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loadlibrary

Load C shared library into MATLAB

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Syntax

loadlibrary(libname,hfile)
loadlibrary(libname)
loadlibrary(libname,hfile,Name,Value)
loadlibrary(libname,@protofile)
[notfound,warnings] = loadlibrary(___)

Description

loadlibrary(libname,hfile) loads functions from C shared library libname defined in header file hfile into MATLAB®. The loadlibrary function only supports calling functions that are callable from C and header files that can be parsed by a C compiler. Functions written in C++ must be declared as extern "C". Alternatively, to call functions in C++ libraries, see Call C++ from MATLAB.

loadlibrary(libname) loads the library if the name of the header file is the same as the name of the library file.

example

loadlibrary(libname,hfile,Name,Value) loads the library with one or more Name,Value arguments.

example

loadlibrary(libname,@protofile) uses a prototype file, protofile, in place of a header file.

example

[notfound,warnings] = loadlibrary(___) returns warning information, and can include any of the input arguments in previous syntaxes.

Examples

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Open Live Script

Add path to examples folder.

addpath(fullfile(matlabroot,'extern','examples','shrlib'))

Display functions in library.

if not(libisloaded('shrlibsample'))
    loadlibrary('shrlibsample')
end
libfunctions('shrlibsample')
Functions in library shrlibsample:

addDoubleRef              addMixedTypes             addStructByRef            addStructFields           allocateStruct            deallocateStruct          exportedDoubleValue       getListOfStrings          multDoubleArray           multDoubleRef             multiplyShort             print2darray              printExportedDoubleValue  readEnum                  stringToUpper

Clean up.

unloadlibrary shrlibsample

Suppose that you have a library, mylib, with the header file, mylib.h. The header file contains the statement, #include header2.h. To use functions defined in header2.h, call loadlibrary with the addheader option.

loadlibrary('mylib','mylib.h','addheader','header2')
Open Live Script
if libisloaded('shrlibsample')
    unloadlibrary('shrlibsample')
else
    addpath(fullfile(matlabroot,'extern','examples','shrlib'))
end

Create an alias name lib for library shrlibsample.

loadlibrary('shrlibsample','shrlibsample.h','alias','lib')

Call function stringToUpper using the alias name.

str = 'This was a Mixed Case string';
calllib('lib','stringToUpper',str)
ans = 
'THIS WAS A MIXED CASE STRING'

Clean up.

unloadlibrary lib

Add path to folder containing shrlibsample and its header file, shrlibsample.h.

addpath(fullfile(matlabroot,'extern','examples','shrlib'))

The shrlibsample.h header file includes the header file, shrhelp.h. If shrhelp.h is in a different folder, for example, c:\work, use the 'includepath' option to tell MATLAB where to find the file.

loadlibrary('shrlibsample','shrlibsample.h','includepath','c:\work')

Cleanup.

unloadlibrary shrlibsample

This example shows how to replace the addMixedTypes function name in the MATLAB shrlibsample library with an alias name, addTypes. To define the alias name, create a prototype file then load the library using the prototype file as the header file.

Use a folder for which you have write-access.

cd('c:\work')

Create a prototype file, mxproto.m.

hfile = fullfile(matlabroot,'extern','examples','shrlib','shrlibsample.h');
[notfound,warnings] = loadlibrary('shrlibsample',hfile,'mfilename','mxproto')

MATLAB creates the prototype file in the current folder. Ignore the warning messages.

Add the alias name to the prototype file. Open the file in MATLAB Editor.

edit mxproto.m

Search for the function addMixedTypes.

The following statement assigns the alias addTypes.

fcns.alias{fcnNum}='addTypes';

Add the statement to the line before the statement to increment fcnNum. The new function prototype, with the new statement shown in bold, looks like the following:

%  double addMixedTypes ( short , int , double ); 
fcns.thunkname{fcnNum}='doubleint16int32doubleThunk';
fcns.name{fcnNum}='addMixedTypes'; 
fcns.calltype{fcnNum}='Thunk'; 
fcns.LHS{fcnNum}='double'; 
fcns.RHS{fcnNum}={'int16', 'int32', 'double'};
fcns.alias{fcnNum}='addTypes'; % Alias defined
fcnNum=fcnNum+1; % Increment fcnNum

Reload shrlibsample using the prototype file.

unloadlibrary shrlibsample
loadlibrary('shrlibsample',@mxproto)

Call the function by its alias name.

calllib('shrlibsample','addTypes',int16(127),int32(33000),pi)
ans = 3.3130e+04

Cleanup.

unloadlibrary shrlibsample

Input Arguments

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Name of shared library, specified as a character vector. The name is case-sensitive and must match the file on your system.

On Microsoft® Windows® systems, libname refers to the name of a shared library (.dll) file. On Linux® systems, it refers to the name of a shared object (.so) file. On Apple Mac systems, it refers to a dynamic shared library (.dylib). If you do not include a file extension with the libname argument, loadlibrary attempts to find the library with either the appropriate platform MEX-file extension or the appropriate platform library extension. For a list of MEX-file extensions, use mexext.

MATLAB extracts the name portion of libname to identify the library in other shared library functions. For example, when you call the calllib function, do not include the path or file extension in the library argument name.

Data Types: char

Name of C header file, specified as a character vector. The name is case-sensitive and must match the file on your system. If you do not include a file extension in the file name, loadlibrary uses .h for the extension.

Data Types: char

Name of prototype file, specified as a character vector. The name is case-sensitive and must match the file on your system. @protofile specifies a function handle to the prototype file. When using a prototype file, the only valid Name,Value pair argument is alias.

Data Types: char

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: loadlibrary('mylib','mylib.h','addheader','header2')

Header file, specified as the comma-separated pair consisting of 'addheader' and a character vector. Specify the file name without a file extension.

Each file specified by addheader must have a corresponding #include statement in the base header file. To load only the functions defined in the header file that you want to use in MATLAB, use addheader.

MATLAB does not verify the existence of header files and ignores any that are not needed.

Alternative name for library, specified as the comma-separated pair consisting of 'alias' and a character vector. Associates the specified name with the library. All subsequent calls to MATLAB functions that reference this library must use this alias until the library is unloaded.

More search paths for subordinate header files—header files within header files, specified as the comma-separated pair consisting of 'includepath' and a character vector.

Prototype file, specified as the comma-separated pair consisting of 'mfilename' and a character vector. Generates a prototype file in the current folder. The prototype file name must be different from the library name. Use this file in place of a header file when loading the library.

Thunk file, specified as the comma-separated pair consisting of 'thunkfilename' and a character vector. Overrides the default thunk file name.

Output Arguments

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Names of functions found in header files but missing from the library, returned as cell array.

Data Types: cell

Warnings produced while processing the header file, returned as character array.

Limitations

  • You must have a supported C compiler and Perl must be available.

  • Do not call loadlibrary if the library is already in memory. To test this condition, call libisloaded.

  • loadlibrary does not support libraries generated by the MATLAB Compiler SDK™ and code generation products like MATLAB Coder.

  • The MATLAB Shared Library interface does not support library functions with function pointer inputs.

  • For more information, see Limitations to Shared Library Support.

More About

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Prototype File

A prototype file is a file of MATLAB commands which you can modify and use in place of a header file.

Thunk File

A thunk file is a compatibility layer to a 64-bit library generated by MATLAB. The name of the thunk file is BASENAME_thunk_COMPUTER.c where BASENAME is either the name of the shared library or, if specified, the mfilename prototype name. COMPUTER is the text returned by the computer function.

MATLAB compiles this file and creates the file BASENAME_thunk_COMPUTER.LIBEXT, where LIBEXT is the platform-dependent default shared library extension, for example, dll on Windows.

Tips

  • If you have more than one library file of the same name, load the first using the library file name. Then load the additional libraries using the alias option.

  • Use the alias option as an alternate name for a library. To load an alternate header file, use the @protofile argument.

Version History

Introduced before R2006a

See Also

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