Libevent
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Libevent
libevent is a software library that provides asynchronous event notification. The libevent API provides a mechanism to execute a callback function when a specific event occurs on a file descriptor or after a timeout has been reached. libevent also supports callbacks triggered by signals and regular timeouts. libevent is meant to replace the event loop found in event-driven network servers. An application can just call event_dispatch() and then add or remove events dynamically without having to change the event loop. Currently, libevent supports /dev/poll, kqueue(2), POSIX select(2), Windows IOCP, poll(2), epoll(7) and Solaris event ports. It also has experimental support for real-time signals. The exposed event API is uniform over all of the supported platforms. As a result, libevent allows for portable application development and provides "the most scalable event notification mechanism available on an operating system". Using callbacks on signals, libevent makes it possibl ...
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Niels Provos
Niels Provos is a German-American researcher in security engineering, malware, and cryptography. He received a PhD in computer science from the University of Michigan. From 2003 to 2018, he worked at Google as a Distinguished Engineer on computer security, security for Google Cloud Platform. In 2018, he left Google to join Stripe (company), Stripe as its new head of security. For many years, Provos contributed to the OpenBSD operating system, where he developed the bcrypt adaptive cryptographic hash function. He is the author of numerous software packages, including the libevent event driven programming system, the Systrace access control system, the honeyd honeypot system, the StegDetect steganography detector, the Bcrypt password encryption technique, and many others. Provos has been an outspoken critic of the effect of the DMCA and similar laws on security researchers, arguing that they threaten to make criminals of people conducting legitimate security research. Provos has al ...
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Epoll
epoll is a Linux kernel system call for a scalable I/O event notification mechanism, first introduced in version 2.5.44 of the Linux kernel. Its function is to monitor multiple file descriptors to see whether I/O is possible on any of them. It is meant to replace the older POSIX select(2) and poll(2) system calls, to achieve better performance in more demanding applications, where the number of watched file descriptors is large (unlike the older system calls, which operate in ''O''(''n'') time, epoll operates in ''O''(1) time). epoll is similar to FreeBSD's kqueue, in that it consists of a set of user-space functions, each taking a file descriptor argument denoting the configurable kernel object, against which they cooperatively operate. epoll uses a red–black tree (RB-tree) data structure to keep track of all file descriptors that are currently being monitored. API int epoll_create1(int flags); Creates an epoll object and returns its file descriptor. The flags parameter allo ...
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Memcached
Memcached (pronounced variously ''mem-cash-dee'' or ''mem-cashed'') is a general-purpose distributed memory-caching system. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read. Memcached is free and open-source software, licensed under the Revised BSD license. Memcached runs on Unix-like operating systems (Linux and macOS) and on Microsoft Windows. It depends on the libevent library. Memcached's APIs provide a very large hash table distributed across multiple machines. When the table is full, subsequent inserts cause older data to be purged in least recently used (LRU) order. Applications using Memcached typically layer requests and additions into RAM before falling back on a slower backing store, such as a database. Memcached has no internal mechanism to track misses which may happen. However, some third party utilities provide this functi ...
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Kqueue
Kqueue is a scalable event notification interface introduced in FreeBSD 4.1 in July 2000, also supported in NetBSD, OpenBSD, DragonFly BSD, and macOS. Kqueue was originally authored in 2000 by Jonathan Lemon, then involved with the FreeBSD Core Team. Kqueue makes it possible for software like nginx to solve the c10k problem. Kqueue provides efficient input and output event pipelines between the kernel and userland. Thus, it is possible to modify event filters as well as receive pending events while using only a single system call to kevent(2) per main event loop iteration. This contrasts with older traditional polling system calls such as poll(2) and select(2) which are less efficient, especially when polling for events on numerous file descriptors. Kqueue not only handles file descriptor events but is also used for various other notifications such as file modification monitoring, signals, asynchronous I/O events (AIO), child process state change monitoring, and timers which su ...
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Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for servers, and Windows IoT for embedded systems. Defunct Windows families include Windows 9x, Windows Mobile, and Windows Phone. The first version of Windows was released on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Windows is the most popular desktop operating system in the world, with 75% market share , according to StatCounter. However, Windows is not the most used operating system when including both mobile and desktop OSes, due to Android's massive growth. , the most recent version of Windows is Windows 11 for consumer PCs and tablets, Windows 11 Enterprise for corporations, and Windows Server 2022 for servers. Genealogy By marketing ...
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Poll(2)
Poll, polled, or polling may refer to: Figurative head counts * Poll, a formal election ** Election verification exit poll, a survey taken to verify election counts ** Polling, voting to make decisions or determine opinions ** Polling places or polling station, a.k.a. the polls, where voters cast their ballots in elections * Poll, a non-formal election: ** Opinion poll, a survey of public opinion ** Exit poll, a survey of voters taken immediately after they have exited the polling stations ** Straw poll, an ad-hoc or unofficial vote ** Survey (human research) Agriculture * Poll (livestock), the top of an animal's head * Polled livestock, hornless livestock of normally horned species * Polling, livestock dehorning Arts, entertainment, and media * Poll (band), a Greek pop group of the 1970s * ''Poll'', the German title for the 2010 film ''The Poll Diaries'' Mathematics, science, and technology * poll (Unix), a Unix system call *POLL, DNA polymerase lambda * Polling (comput ...
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Ntpd
The Network Time Protocol daemon (ntpd) is an operating system program that maintains the system time in synchronization with time servers using the Network Time Protocol (NTP). Description The ntpd program is an operating-system daemon that sets and maintains a computer system's system time in synchronization with Internet-standard time servers. It is a complete implementation of the Network Time Protocol (NTP) version 4, but retains compatibility with versions 1, 2, and 3 as defined by RFC 1059, RFC 1119, and RFC 1305, respectively. ntpd performs most computations in 64-bit floating point arithmetic and uses 64-bit fixed point operations only when necessary to preserve the ultimate precision, about 232 picoseconds. While ordinary workstations and networks cannot achieve the ultimate precision , future processors and networks may require it. xntpd is the Network Time Protocol version three (1992) daemon software. The "x" was added to the name because the branch of code that eve ...
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Transmission (BitTorrent Client)
Transmission is a BitTorrent client which features a variety of user interfaces on top of a cross-platform back-end. Transmission is free software licensed under the terms of the GNU General Public License, with parts under the MIT License. Features Transmission allows users to quickly download files from multiple peers on the Internet and to upload their own files. By adding torrent files via the user interface, users can create a queue of files to be downloaded and uploaded. Within the file selection menus, users can customise their downloads at the level of individual files. Transmission also seeds, that is, it will automatically share downloaded content. Transmission allows the assigning of priorities to torrents and to files within torrents, thus potentially influencing which files download first. It supports the Magnet URI scheme and encrypted connections. It allows torrent-file creation and peer exchange compatible with Vuze and μTorrent. It includes a built-in web se ...
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Cross-platform
In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software requires a separate build for each platform, but some can be directly run on any platform without special preparation, being written in an interpreted language or compiled to portable bytecode for which the interpreters or run-time packages are common or standard components of all supported platforms. For example, a cross-platform application may run on Microsoft Windows, Linux, and macOS. Cross-platform software may run on many platforms, or as few as two. Some frameworks for cross-platform development are Codename One, Kivy, Qt, Flutter, NativeScript, Xamarin, Phonegap, Ionic, and React Native. Platforms ''Platform'' can refer to the type of processor (CPU) or other hardware on which an operating system (OS) or application runs, t ...
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Google Chrome
Google Chrome is a cross-platform web browser developed by Google. It was first released in 2008 for Microsoft Windows, built with free software components from Apple WebKit and Mozilla Firefox. Versions were later released for Linux, macOS, iOS, and also for Android, where it is the default browser. The browser is also the main component of ChromeOS, where it serves as the platform for web applications. Most of Chrome's source code comes from Google's free and open-source software project ''Chromium'', but Chrome is licensed as proprietary freeware. WebKit was the original rendering engine, but Google eventually forked it to create the Blink engine; all Chrome variants except iOS now use Blink. , StatCounter estimates that Chrome has a 67% worldwide browser market share (after peaking at 72.38% in November 2018) on personal computers (PC), is most used on tablets (having surpassed Safari), and is also dominant on smartphones and at 65% across all platforms combined. ...
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BSD License
BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD license was used for its namesake, the Berkeley Software Distribution (BSD), a Unix-like operating system. The original version has since been revised, and its descendants are referred to as modified BSD licenses. BSD is both a license and a class of license (generally referred to as BSD-like). The modified BSD license (in wide use today) is very similar to the license originally used for the BSD version of Unix. The BSD license is a simple license that merely requires that all code retain the BSD license notice if redistributed in source code format, or reproduce the notice if redistributed in binary format. The BSD license (unlike some other licenses e.g. GPL) does not require that source code be distributed at all. Terms In addition t ...
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Context (computing)
In computer science, a task context is the minimal set of data used by a task (which may be a process, thread, or fiber) that must be saved to allow a task to be interrupted, and later continued from the same point. The concept of context assumes significance in the case of interruptible tasks, wherein, upon being interrupted, the processor saves the context and proceeds to serve the interrupt service routine. Thus, the smaller the context is, the smaller the latency is. The context data may be located in processor registers, memory used by the task, or in control registers used by some operating systems to manage the task. The storage memory (files used by a task) is not concerned by the "task context" in the case of a context switch, even if this can be stored for some uses (checkpointing). Context types In some computer languages like C#, there is also the concept of ''safe''/''secure context''. For instance, if an array is needed inside a structure, it can be added to it si ...
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