The Apache Portable Runtime (APR) is a supporting library for the Apache

Apache HTTP Server

The Apache HTTP Server, commonly referred to as Apache , is web server software notable for playing a key role in the initial growth of the World Wide Web. In 2009 it became the first web server software to surpass the 100 million website milestone...

 web server

Web server

Web server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....

. It provides a set of APIs that map to the underlying operating system (OS). Where the OS doesn't support a particular function, APR will provide an emulation. Thus programmers can use the APR to make a program truly portable across platforms.

APR originally formed a part of Apache HTTP Server

Apache HTTP Server

The Apache HTTP Server, commonly referred to as Apache , is web server software notable for playing a key role in the initial growth of the World Wide Web. In 2009 it became the first web server software to surpass the 100 million website milestone...

, but the Apache Software Foundation

Apache Software Foundation

The Apache Software Foundation is a non-profit corporation to support Apache software projects, including the Apache HTTP Server. The ASF was formed from the Apache Group and incorporated in Delaware, U.S., in June 1999.The Apache Software Foundation is a decentralized community of developers...

 spun it off into a separate project. Other applications can use it to achieve platform independence.

Functionality

The range of platform-independent functionality provided by APR includes:

• Memory allocation and memory pool
  Memory pool
  Memory pools, also called fixed-size-blocks allocation, allow dynamic memory allocation comparable to malloc or C++'s operator new. As those implementations suffer from fragmentation because of variable block sizes, it can be impossible to use them in a real time system due to performance...
  
   functionality
• Atomic operations
• Dynamic library
  Library (computer science)
  In computer science, a library is a collection of resources used to develop software. These may include pre-written code and subroutines, classes, values or type specifications....
  
   handling
• File I/O
  I/O
  I/O may refer to:* Input/output, a system of communication for information processing systems* Input-output model, an economic model of flow prediction between sectors...
  
  
• Command-argument parsing
• Locking
• Hash table
  Hash table
  In computer science, a hash table or hash map is a data structure that uses a hash function to map identifying values, known as keys , to their associated values . Thus, a hash table implements an associative array...
  
  s and arrays
• Mmap
  Mmap
  In computing, mmap is a POSIX-compliant Unix system call that maps files or devices into memory. It is a method of memory-mapped file I/O. It naturally implements demand paging, because initially file contents are not entirely read from disk and do not use physical RAM at all...
  
   functionality
• Network sockets
  Berkeley sockets
  The Berkeley sockets application programming interface comprises a library for developing applications in the C programming language that perform inter-process communication, most commonly for communications across a computer network....
  
   and protocols
• Thread
  Thread (computer science)
  In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
  
  , process
  Process (computing)
  In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
  
   and mutex
  Mutual exclusion
  Mutual exclusion algorithms are used in concurrent programming to avoid the simultaneous use of a common resource, such as a global variable, by pieces of computer code called critical sections. A critical section is a piece of code in which a process or thread accesses a common resource...
  
   functionality
• Shared memory
  Shared memory
  In computing, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Depending on context, programs may run on a single processor or on multiple separate processors...
  
   functionality
• Time routines
• User and group ID services

Similar projects

• Glib
  GLib
  GLib is a cross-platform software utility library that began as part of the GTK+ project. However, before releasing version 2 of GTK+, the project's developers decided to separate non-GUI-specific code from the GTK+ platform, thus creating GLib as a separate product...
  
   provides similar functionality. It supports many more data structures and OS-independent functions, but fewer IPC
  Inter-process communication
  In computing, Inter-process communication is a set of methods for the exchange of data among multiple threads in one or more processes. Processes may be running on one or more computers connected by a network. IPC methods are divided into methods for message passing, synchronization, shared...
  
  -related functions. (Glib lacks local and global locking and shared-memory management.)
• NSPR is a cross-platform abstraction library used by the Mozilla
  Mozilla
  Mozilla is a term used in a number of ways in relation to the Mozilla.org project and the Mozilla Foundation, their defunct commercial predecessor Netscape Communications Corporation, and their related application software....
  
   project. It is used by another subproject of Mozilla
  Mozilla
  Mozilla is a term used in a number of ways in relation to the Mozilla.org project and the Mozilla Foundation, their defunct commercial predecessor Netscape Communications Corporation, and their related application software....
  
   XPFE to provide cross-platform graphical user interface
  Graphical user interface
  In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
  
   (GUI) functionality.
• Adaptive Communication Environment
  Adaptive Communication Environment
  The Adaptive Communication Environment is an open-source framework used to simplify various aspects of network programming...
  
   (ACE) is an object-oriented library written in C++ similar in functionality to APR. It is widely deployed in commercial products.
• commonc++ is a cross-platform C++ class library for systems programming, with much of the same functionality as APR.
• POCO
  POCO C++ Libraries
  The POCO C++ Libraries are a collection of open source class libraries for developing network-centric, portable applications in C++. POCO stands for POrtable COmponents...
  
   is a modern C++ framework similar in concept but more extensive than APR.
• WxWidgets
  WxWidgets
  wxWidgets is a widget toolkit for creating graphical user interfaces for cross-platform applications. wxWidgets enables a program's GUI code to compile and run on several computer platforms with minimal or no code changes...
  
   is an object-oriented cross-platform GUI library that also provides abstraction classes for database communication, IPC
  Inter-process communication
  In computing, Inter-process communication is a set of methods for the exchange of data among multiple threads in one or more processes. Processes may be running on one or more computers connected by a network. IPC methods are divided into methods for message passing, synchronization, shared...
  
   and networking functionality.
• Qt
  Qt (toolkit)
  Qt is a cross-platform application framework that is widely used for developing application software with a graphical user interface , and also used for developing non-GUI programs such as command-line tools and consoles for servers...
  
  , a cross-platform application development framework with similar features, can also foster GUI
  Gui
  Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...
  
   development.

External links

• The current APR programming documentation
• The Apache Software Foundation website
• APR programming tutorial
• APR wikibooks tutorial (inactive)