传递指针参数在MATLAB到C-DLL函数foo（CHAR **） [英] Passing pointer argument in MATLAB to a C-DLL function foo(char**)

问题描述

我写一个C-DLL是从MATLAB调用。
它是可调用为const char ** 参数的函数？例如。

I am writing a C-DLL to be called from MATLAB. Is it possible to call a function with const char ** parameter? e.g.

void myGetVersion( const char ** );

的C code将是：

The C code would be:

const char *version=0;
myGetVersion( &version );

什么会相应MATLAB- code（如果可能的话）？

What would be corresponding MATLAB-Code (if it is possible at all)?

非常感谢你！

P.S .:
我觉得这是帮助页面，但我不能发现我的情况： - （

P.S.: I think this is the help page, but I couldn't find my case :-(

推荐答案

答案是使用的 LIBPOINTER 功能<一个href=\"http://stackoverflow.com/questions/7445054/passing-pointer-argument-in-matlab-to-a-c-dll-function-foochar/7445529#7445529\">@JonasHeidelberg建议。让我展开他的工作的例子..解

The answer is to build a pointer to a c-string using the LIBPOINTER function as @JonasHeidelberg suggested. Let me expand his solution with a working example..

首先让我们建立一个简单的DLL：

First lets build a simple DLL:

#ifndef VERSION_H
#define VERSION_H

#ifdef __cplusplus
extern "C" {
#endif

#ifdef _WIN32
#   ifdef BUILDING_DLL
#       define DLL_IMPORT_EXPORT __declspec(dllexport)
#   else
#       define DLL_IMPORT_EXPORT __declspec(dllimport)
#   endif
#else
#   define DLL_IMPORT_EXPORT
#endif

DLL_IMPORT_EXPORT void myGetVersion(char**str);

#ifdef __cplusplus
}
#endif

#endif

version.c

#include "version.h"
#include <string.h>

DLL_IMPORT_EXPORT void myGetVersion(char **str)
{
    *str = strdup("1.0.0");
}

您可以使用preferred编译器来构建DLL库（Visual Studio中，MinGW的GCC ..）。我使用MinGW的编译上面的，下面是我使用生成文件：

You can use your preferred compiler to build the DLL library (Visual Studio, MinGW GCC, ..). I am using MinGW to compile the above, here is the makefile I am using:

CC = gcc

all: main

libversion.dll: version.c
    $(CC) -DBUILDING_DLL version.c -I. -shared -o libversion.dll

main: libversion.dll main.c
    $(CC) main.c -o main -L. -lversion

clean:
    rm -rf *.o *.dll *.exe

在我们转移到MATLAB，让一个C程序测试库：

Before we move to MATLAB, lets test the library with a C program:

#include <stdio.h>
#include <stdlib.h>
#include "version.h"

int main()
{
    char *str = NULL;
    myGetVersion(&str);
    printf("%s\n", str);
    free(str);

    return 0;
}

现在，所有的工作，这里是如何使用该库从MATLAB：

Now that all is working, here is how to use this library from MATLAB:

%# load DLL and check exported functions
loadlibrary libversion.dll version.h
assert( libisloaded('libversion') )
libfunctions libversion -full

%# pass c-string by reference
pstr = libpointer('stringPtrPtr',{''}); %# we use a cellarray of strings
get(pstr)
calllib('libversion','myGetVersion',pstr)
dllVersion = pstr.Value{1}

%# unload DLL
unloadlibrary libversion

以字符串返回的输出：

The output with the string returned:

Functions in library libversion:
stringPtrPtr myGetVersion(stringPtrPtr)

       Value: {''}
    DataType: 'stringPtrPtr'

dllVersion =
1.0.0

这篇关于传递指针参数在MATLAB到C-DLL函数foo（CHAR **）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！