The Simplified Wrapper and Interface Generator (SWIG) is an
open-source software
Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. Op ...
tool used to connect
computer program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components.
A computer program ...
s or
libraries
A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...
written in
C or
C++
C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
with
scripting language
A scripting language or script language is a programming language that is used to manipulate, customize, and automate the facilities of an existing system. Scripting languages are usually interpreted at runtime rather than compiled.
A scripting ...
s such as
Lua
Lua or LUA may refer to:
Science and technology
* Lua (programming language)
* Latvia University of Agriculture
* Last universal ancestor, in evolution
Ethnicity and language
* Lua people, of Laos
* Lawa people, of Thailand sometimes referred t ...
,
Perl
Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offici ...
,
PHP
PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group ...
,
Python
Python may refer to:
Snakes
* Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia
** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia
* Python (mythology), a mythical serpent
Computing
* Python (pro ...
,
R,
Ruby
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sa ...
,
Tcl
TCL or Tcl or TCLs may refer to:
Business
* TCL Technology, a Chinese consumer electronics and appliance company
**TCL Electronics, a subsidiary of TCL Technology
* Texas Collegiate League, a collegiate baseball league
* Trade Centre Limited ...
, and other languages like
C#,
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
,
JavaScript
JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of Website, websites use JavaScript on the Client (computing), client side ...
,
Go,
D,
OCaml
OCaml ( , formerly Objective Caml) is a general-purpose programming language, general-purpose, multi-paradigm programming language which extends the Caml dialect of ML (programming language), ML with object-oriented programming, object-oriented ...
,
Octave
In music, an octave ( la, octavus: eighth) or perfect octave (sometimes called the diapason) is the interval between one musical pitch and another with double its frequency. The octave relationship is a natural phenomenon that has been refer ...
,
Scilab
Scilab is a free and open-source, cross-platform numerical computational package and a high-level, numerically oriented programming language. It can be used for signal processing, statistical analysis, image enhancement, fluid dynamics simulat ...
and
Scheme A scheme is a systematic plan for the implementation of a certain idea.
Scheme or schemer may refer to:
Arts and entertainment
* ''The Scheme'' (TV series), a BBC Scotland documentary series
* The Scheme (band), an English pop band
* ''The Schem ...
. Output can also be in the form of
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. T ...
.
Function
The aim is to allow the calling of native functions (that were written in C or C++) by other programming languages, passing complex data types to those functions, keeping memory from being inappropriately freed, inheriting object classes across languages, etc. The programmer writes an interface file containing a list of C/C++ functions to be made visible to an interpreter. SWIG will compile the interface file and generate code in regular C/C++ and the target programming language. SWIG will generate
conversion code for functions with simple arguments; conversion code for complex types of arguments must be written by the programmer. The SWIG tool creates
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...
that provides the glue between C/C++ and the target language. Depending on the language, this glue comes in two forms:
*a
shared library
In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subr ...
that an extant interpreter can link to as some form of extension module, or
*a shared library that can be linked to other programs compiled in the target language (for example, using
Java Native Interface
In software design, the Java Native Interface (JNI) is a foreign function interface programming framework that enables Java code running in a Java virtual machine (JVM) to call and be called by
native applications (programs specific to a hardwa ...
(JNI) in Java).
SWIG is not used for calling interpreted functions by native code; this must be done by the programmer manually.
Example
SWIG wraps simple C declarations by creating an interface that closely matches the way in which the declarations would be used in a C program. For example, consider the following interface file:
%module example
%inline %
#define STATUS 50
#define VERSION "1.1"
In this file, there are two functions and , a global variable , and two constants and . When SWIG creates an extension module, these declarations are accessible as scripting language functions, variables, and constants respectively. In Python:
>>> example.sin(3)
0.141120008
>>> example.strcmp('Dave','Mike')
-1
>>> print(example.cvar.Foo)
42
>>> print(example.STATUS)
50
>>> print(example.VERSION)
1.1
Purpose
There are two main reasons to embed a
scripting engine
A scripting language or script language is a programming language that is used to manipulate, customize, and automate the facilities of an existing system. Scripting languages are usually interpreted at runtime rather than compiled.
A scripting ...
in an existing C/C++ program:
*The program can then be customized far faster,
via a scripting language instead of C/C++. The scripting engine may even be exposed to the end-user, so that they can automate common tasks by writing scripts.
*Even if the final product is not to contain the scripting engine, it may nevertheless be very useful for writing test scripts.
There are several reasons to create dynamic libraries that can be loaded into extant interpreters, including:
*Provide access to a C/C++
library
A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...
which has no equivalent in the scripting language.
*Write the whole program in the scripting language first, and after
profiling, rewrite performance-critical code in C or C++.
History
SWIG is written in C and C++ and has been publicly available since February 1996. The initial author and main developer was
David M. Beazley who developed SWIG while working as a graduate student at
Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
and the
University of Utah
The University of Utah (U of U, UofU, or simply The U) is a public research university in Salt Lake City, Utah. It is the flagship institution of the Utah System of Higher Education. The university was established in 1850 as the University of De ...
and while on the faculty at the
University of Chicago
The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...
. Development is currently supported by an active group of volunteers led by William Fulton. SWIG has been released under a
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...
.
Google Summer of Code
SWIG was a successful participant of
Google Summer of Code
The Google Summer of Code, often abbreviated to GSoC, is an international annual program in which Google awards stipends to contributors who successfully complete a free and open-source software coding project during the summer. , the program is ...
in 2008, 2009, 2012. In 2008, SWIG got four slots. Haoyu Bai spent his summers on SWIG's Python 3.0 Backend, Jan Jezabek worked on Support for generating
COM
Com or COM may refer to:
Computing
* COM (hardware interface), a serial port interface on IBM PC-compatible computers
* COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS
* .com, an Internet top-level d ...
wrappers, Cheryl Foil spent her time on Comment 'Translator' for SWIG, and Maciej Drwal worked on a C backend.
In 2009, SWIG again participated in Google Summer of Code. This time four students participated. Baozeng Ding worked on a
Scilab
Scilab is a free and open-source, cross-platform numerical computational package and a high-level, numerically oriented programming language. It can be used for signal processing, statistical analysis, image enhancement, fluid dynamics simulat ...
module. Matevz Jekovec spent time on
C++0x
C++11 is a version of the ISO/IEC 14882 standard for the C++ programming language. C++11 replaced the prior version of the C++ standard, called C++03, and was later replaced by C++14. The name follows the tradition of naming language versions b ...
features. Ashish Sharma spent his summer on an
Objective-C
Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTS ...
module, Miklos Vajna spent his time on PHP directors.
In 2012, SWIG participated in Google Summer of Code. This time four out of five students successfully completed the project. Leif Middelschulte worked on a C target language module. Swati Sharma enhanced the Objective-C module. Neha Narang added the new module on JavaScript. Dmitry Kabak worked on source code documentation and
Doxygen
Doxygen ( ) is a documentation generator and static analysis tool for software source trees. When used as a documentation generator, Doxygen extracts information from specially-formatted comments within the code. When used for analysis, Doxyge ...
comments.
Alternatives
For Python, similar functionality is offered by
SIP and
Boost's Boost.python library.
Projects Using SWIG
*
ZXID
ZXID.org Identity Management toolkit implements standalone SAML 2.0,
Liberty ID-WSF, ID-WSF 2.0, and XACML 2.0 stacks and aims at implementing all popular
federation, Single sign-on, SSO, and ID Web Services protocols. It is a C implementation
...
(Apache License, Version 2.0)
*Symlabs SFIS (commercial)
*
LLDB
*
GNU Radio
GNU Radio is a free software development toolkit that provides signal processing blocks to implement software-defined radios and signal processing, signal-processing systems. It can be used with external Radio frequency, RF hardware to create soft ...
*
Xapian
Xapian is a free and open-source probabilistic information retrieval library, released under the GNU General Public License (GPL). It is a full-text search engine library for programmers.
It is written in C++, with bindings to allow use from ...
*
TensorFlow
TensorFlow is a free and open-source software library for machine learning and artificial intelligence. It can be used across a range of tasks but has a particular focus on training and inference of deep neural networks. "It is machine learnin ...
*
Apache SINGA
*
QuantLib
*
Babeltrace
See also
*
Language binding
In programming and software design, binding is an application programming interface (API) that provides glue code specifically made to allow a programming language to use a foreign library or operating system service (one that is not native to th ...
*
Foreign function interface
A foreign function interface (FFI) is a mechanism by which a program written in one programming language can call routines or make use of services written in another.
Naming
The term comes from the specification for Common Lisp, which explicit ...
*
Calling convention
In computer science, a calling convention is an implementation-level (low-level) scheme for how subroutines or functions receive parameters from their caller and how they return a result. When some code calls a function, design choices have been ...
*
Name mangling
In compiler construction, name mangling (also called name decoration) is a technique used to solve various problems caused by the need to resolve unique names for programming entities in many modern programming languages.
It provides a way of e ...
*
Application programming interface
An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...
*
Application binary interface
In computer software, an application binary interface (ABI) is an interface between two binary program modules. Often, one of these modules is a library or operating system facility, and the other is a program that is being run by a user.
An ' ...
*
Comparison of application virtual machines
Application virtualization software refers to both application virtual machines and software responsible for implementing them. Application virtual machines are typically used to allow application bytecode to run portably on many different comput ...
*
Wrapper function
A wrapper function is a function (another word for a ''subroutine'') in a software library or a computer program whose main purpose is to call a second subroutine or a system call with little or no additional computation. Wrapper functions are us ...
*
GIWS for the opposite of SWIG: calling Java from C/C++
References
Further reading
*Article
Expose Your C/C++ Program's Internal API with a Quick SWIG by Victor Volkman
*Article
by Michael Fötsch
*Presentation
Application overview for openSUSE by Klaus Kämpf
External links
*{{Official website
Cross-platform software
Free computer programming tools
Programming tools
Scripting languages