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loadlibrary.c

/* loader-loadlibrary.c --  dynamic linking for Win32

   Copyright (C) 1998, 1999, 2000, 2004, 2005, 2006,
                 2007, 2008 Free Software Foundation, Inc.
   Written by Thomas Tanner, 1998

   NOTE: The canonical source of this file is maintained with the
   GNU Libtool package.  Report bugs to bug-libtool@gnu.org.

GNU Libltdl is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

As a special exception to the GNU Lesser General Public License,
if you distribute this file as part of a program or library that
is built using GNU Libtool, you may include this file under the
same distribution terms that you use for the rest of that program.

GNU Libltdl is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with GNU Libltdl; see the file COPYING.LIB.  If not, a
copy can be downloaded from  http://www.gnu.org/licenses/lgpl.html,
or obtained by writing to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

#include "lt__private.h"
#include "lt_dlloader.h"

#if defined(__CYGWIN__)
# include <sys/cygwin.h>
#endif

/* Use the preprocessor to rename non-static symbols to avoid namespace
   collisions when the loader code is statically linked into libltdl.
   Use the "<module_name>_LTX_" prefix so that the symbol addresses can
   be fetched from the preloaded symbol list by lt_dlsym():  */
#define get_vtable      loadlibrary_LTX_get_vtable

LT_BEGIN_C_DECLS
LT_SCOPE lt_dlvtable *get_vtable (lt_user_data loader_data);
LT_END_C_DECLS


/* Boilerplate code to set up the vtable for hooking this loader into
   libltdl's loader list:  */
static int   vl_exit  (lt_user_data loader_data);
static lt_module vm_open  (lt_user_data loader_data, const char *filename,
                           lt_dladvise advise);
static int   vm_close (lt_user_data loader_data, lt_module module);
static void *      vm_sym   (lt_user_data loader_data, lt_module module,
                    const char *symbolname);

static lt_dlinterface_id iface_id = 0;
static lt_dlvtable *vtable = 0;

/* Return the vtable for this loader, only the name and sym_prefix
   attributes (plus the virtual function implementations, obviously)
   change between loaders.  */
lt_dlvtable *
get_vtable (lt_user_data loader_data)
{
  if (!vtable)
    {
      vtable = (lt_dlvtable *) lt__zalloc (sizeof *vtable);
      iface_id = lt_dlinterface_register ("ltdl loadlibrary", NULL);
    }

  if (vtable && !vtable->name)
    {
      vtable->name            = "lt_loadlibrary";
      vtable->module_open     = vm_open;
      vtable->module_close    = vm_close;
      vtable->find_sym        = vm_sym;
      vtable->dlloader_exit   = vl_exit;
      vtable->dlloader_data   = loader_data;
      vtable->priority        = LT_DLLOADER_APPEND;
    }

  if (vtable && (vtable->dlloader_data != loader_data))
    {
      LT__SETERROR (INIT_LOADER);
      return 0;
    }

  return vtable;
}



/* --- IMPLEMENTATION --- */


#include <windows.h>

/* A function called through the vtable when this loader is no
   longer needed by the application.  */
static int
vl_exit (lt_user_data LT__UNUSED loader_data)
{
  vtable = NULL;
  return 0;
}

/* A function called through the vtable to open a module with this
   loader.  Returns an opaque representation of the newly opened
   module for processing with this loader's other vtable functions.  */
static lt_module
vm_open (lt_user_data LT__UNUSED loader_data, const char *filename,
         lt_dladvise LT__UNUSED advise)
{
  lt_module module         = 0;
  char            *ext;
  char            wpath[MAX_PATH];
  size_t    len;

  if (!filename)
    {
      /* Get the name of main module */
      *wpath = 0;
      GetModuleFileName (NULL, wpath, sizeof (wpath));
      filename = wpath;
    }
  else
    {
      len = LT_STRLEN (filename);

      if (len >= MAX_PATH)
        {
        LT__SETERROR (CANNOT_OPEN);
        return 0;
      }

#if HAVE_DECL_CYGWIN_CONV_PATH
      if (cygwin_conv_path (CCP_POSIX_TO_WIN_A, filename, wpath, MAX_PATH))
      {
        LT__SETERROR (CANNOT_OPEN);
        return 0;
      }
      len = 0;
#elif defined(__CYGWIN__)
      cygwin_conv_to_full_win32_path (filename, wpath);
      len = 0;
#else
      strcpy(wpath, filename);
#endif

      ext = strrchr (wpath, '.');
      if (!ext)
      {
        /* Append a `.' to stop Windows from adding an
           implicit `.dll' extension. */
        if (!len)
          len = LT_STRLEN (wpath);

        if (len + 1 >= MAX_PATH)
          {
            LT__SETERROR (CANNOT_OPEN);
            return 0;
          }

        wpath[len] = '.';
        wpath[len+1] = '\0';
      }
    }

  {
    /* Silence dialog from LoadLibrary on some failures.
       No way to get the error mode, but to set it,
       so set it twice to preserve any previous flags. */
    UINT errormode = SetErrorMode(SEM_FAILCRITICALERRORS);
    SetErrorMode(errormode | SEM_FAILCRITICALERRORS);

    module = LoadLibrary (wpath);

    /* Restore the error mode. */
    SetErrorMode(errormode);
  }

  /* libltdl expects this function to fail if it is unable
     to physically load the library.  Sadly, LoadLibrary
     will search the loaded libraries for a match and return
     one of them if the path search load fails.

     We check whether LoadLibrary is returning a handle to
     an already loaded module, and simulate failure if we
     find one. */
  {
    lt_dlhandle cur = 0;

    while ((cur = lt_dlhandle_iterate (iface_id, cur)))
      {
        if (!cur->module)
          {
            cur = 0;
            break;
          }

        if (cur->module == module)
          {
            break;
          }
      }

    if (cur || !module)
      {
        LT__SETERROR (CANNOT_OPEN);
        module = 0;
      }
  }

  return module;
}


/* A function called through the vtable when a particular module
   should be unloaded.  */
static int
vm_close (lt_user_data LT__UNUSED loader_data, lt_module module)
{
  int errors = 0;

  if (FreeLibrary((HMODULE) module) == 0)
    {
      LT__SETERROR (CANNOT_CLOSE);
      ++errors;
    }

  return errors;
}


/* A function called through the vtable to get the address of
   a symbol loaded from a particular module.  */
static void *
vm_sym (lt_user_data LT__UNUSED loader_data, lt_module module, const char *name)
{
  void *address = (void *) GetProcAddress ((HMODULE) module, name);

  if (!address)
    {
      LT__SETERROR (SYMBOL_NOT_FOUND);
    }

  return address;
}

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