/******************************************************************************

 *

 * Project:  Common Portability Library

 * Purpose:  Fetch a function pointer from a shared library / DLL.

 * Author:   Frank Warmerdam, warmerdam@pobox.com

 *

 ******************************************************************************

 * Copyright (c) 1999, Frank Warmerdam

 * Copyright (c) 2009-2013, Even Rouault <even dot rouault at spatialys.com>

 *

 * SPDX-License-Identifier: MIT

 ****************************************************************************/

#include "cpl_port.h"

#include "cpl_conv.h"

#include <cstddef>

#include "cpl_config.h"

#include "cpl_error.h"

#include "cpl_string.h"

/* ==================================================================== */

/*                  Unix Implementation                                 */

/* ==================================================================== */

/* MinGW32 might define HAVE_DLFCN_H, so skip the unix implementation */

#if defined(HAVE_DLFCN_H) && !defined(_WIN32)

#define GOT_GETSYMBOL

#include <dlfcn.h>

/************************************************************************/

/*                            CPLGetSymbol()                            */

/************************************************************************/

/**

 * Fetch a function pointer from a shared library / DLL.

 *

 * This function is meant to abstract access to shared libraries and

 * DLLs and performs functions similar to dlopen()/dlsym() on Unix and

 * LoadLibrary() / GetProcAddress() on Windows.

 *

 * If no support for loading entry points from a shared library is available

 * this function will always return NULL.   Rules on when this function

 * issues a CPLError() or not are not currently well defined, and will have

 * to be resolved in the future.

 *

 * Currently CPLGetSymbol() doesn't try to:

 * <ul>

 *  <li> prevent the reference count on the library from going up

 *    for every request, or given any opportunity to unload

 *    the library.

 *  <li> Attempt to look for the library in non-standard

 *    locations.

 *  <li> Attempt to try variations on the symbol name, like

 *    pre-pending or post-pending an underscore.

 * </ul>

 *

 * Some of these issues may be worked on in the future.

 *

 * @param pszLibrary the name of the shared library or DLL containing

 * the function.  May contain path to file.  If not system supplies search

 * paths will be used.

 * @param pszSymbolName the name of the function to fetch a pointer to.

 * @return A pointer to the function if found, or NULL if the function isn't

 * found, or the shared library can't be loaded.

 */

void *CPLGetSymbol(const char *pszLibrary, const char *pszSymbolName)

{

    void *pLibrary = dlopen(pszLibrary, RTLD_LAZY);

    if (pLibrary == nullptr)

    {

        CPLError(CE_Failure, CPLE_AppDefined, "%s", dlerror());

        return nullptr;

    }

    void *pSymbol = dlsym(pLibrary, pszSymbolName);

#if (defined(__APPLE__) && defined(__MACH__))

    /* On mach-o systems, C symbols have a leading underscore and depending

     * on how dlcompat is configured it may or may not add the leading

     * underscore.  If dlsym() fails, add an underscore and try again.

     */

    if (pSymbol == nullptr)

    {

        char withUnder[256] = {};

        snprintf(withUnder, sizeof(withUnder), "_%s", pszSymbolName);

        pSymbol = dlsym(pLibrary, withUnder);

    }

#endif

    if (pSymbol == nullptr)

    {

        CPLError(CE_Failure, CPLE_AppDefined, "%s", dlerror());

        // Do not call dlclose here.  misc.py:misc_6() demonstrates the crash.

        // coverity[leaked_storage]

        return nullptr;

    }

    // coverity[leaked_storage]  It is not safe to call dlclose.

    return (pSymbol);

}

#endif /* def __unix__ && defined(HAVE_DLFCN_H) */

/* ==================================================================== */

/*                 Windows Implementation                               */

/* ==================================================================== */

#if defined(_WIN32)

#define GOT_GETSYMBOL

#include <windows.h>

/************************************************************************/

/*                            CPLGetSymbol()                            */

/************************************************************************/

void *CPLGetSymbol(const char *pszLibrary, const char *pszSymbolName)

{

    void *pLibrary = nullptr;

    void *pSymbol = nullptr;

    // Avoid error boxes to pop up (#5211, #5525).

    UINT uOldErrorMode =

        SetErrorMode(SEM_NOOPENFILEERRORBOX | SEM_FAILCRITICALERRORS);

#if defined(_MSC_VER) || __MSVCRT_VERSION__ >= 0x0601

    if (CPLTestBool(CPLGetConfigOption("GDAL_FILENAME_IS_UTF8", "YES")))

    {

        wchar_t *pwszFilename =

            CPLRecodeToWChar(pszLibrary, CPL_ENC_UTF8, CPL_ENC_UCS2);

        pLibrary = LoadLibraryW(pwszFilename);

        CPLFree(pwszFilename);

    }

    else

#endif

    {

        pLibrary = LoadLibraryA(pszLibrary);

    }

    if (pLibrary <= (void *)HINSTANCE_ERROR)

    {

        LPVOID lpMsgBuf = nullptr;

        int nLastError = GetLastError();

        // Restore old error mode.

        SetErrorMode(uOldErrorMode);

        FormatMessage(

            FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |

                FORMAT_MESSAGE_IGNORE_INSERTS,

            nullptr, nLastError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),

            reinterpret_cast<LPTSTR>(&lpMsgBuf), 0, nullptr);

        CPLError(CE_Failure, CPLE_AppDefined,

                 "Can't load requested DLL: %s\n%d: %s", pszLibrary, nLastError,

                 static_cast<const char *>(lpMsgBuf));

        return nullptr;

    }

    // Restore old error mode.

    SetErrorMode(uOldErrorMode);

    pSymbol = reinterpret_cast<void *>(

        GetProcAddress(static_cast<HINSTANCE>(pLibrary), pszSymbolName));

    if (pSymbol == nullptr)

    {

        CPLError(CE_Failure, CPLE_AppDefined,

                 "Can't find requested entry point: %s", pszSymbolName);

        return nullptr;

    }

    return (pSymbol);

}

#endif  // def _WIN32

/* ==================================================================== */

/*      Dummy implementation.                                           */

/* ==================================================================== */

#ifndef GOT_GETSYMBOL

/************************************************************************/

/*                            CPLGetSymbol()                            */

/*                                                                      */

/*      Dummy implementation.                                           */

/************************************************************************/

void *CPLGetSymbol(const char *pszLibrary, const char *pszEntryPoint)

{

    CPLDebug("CPL",

             "CPLGetSymbol(%s,%s) called.  Failed as this is stub"

             " implementation.",

             pszLibrary, pszEntryPoint);

    return nullptr;

}

#endif