Add ws_load_library and ws_module_open, which respectively call

LoadLibrary and g_module_open only for the program directory and system
directory on Windows. Use them to replace a bunch of LoadLibrary and
g_module_open calls. Use the extension ".dll" for all the DLLs that we
load. Add comments about DLL loading in Python.

svn path=/trunk/; revision=33924

3 files changed, 134 insertions, 2 deletions

diff --git a/wsutil/file_util.c b/wsutil/file_util.c
index d145752c83..0c57efbe19 100644
--- a/wsutil/file_util.c
+++ b/wsutil/file_util.c
@@ -48,8 +48,8 @@
 
 #include "file_util.h"
 
-
-
+static gchar *program_path = NULL;
+static gchar *system_path = NULL;
 
 /**
  * g_open:
@@ -441,3 +441,113 @@ ws_stdio_freopen (const gchar *filename,
       errno = save_errno;
       return retval;
 }
+
+
+/* DLL loading */
+static gboolean
+init_dll_load_paths() {
+      TCHAR path_pfx[MAX_PATH];
+      
+      if (program_path && system_path)
+	    return TRUE;
+
+      /* XXX - Duplicate code in filesystem.c:init_progfile_dir */
+      if (GetModuleFileName(NULL, path_pfx, MAX_PATH) == 0 || GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+	    return FALSE;
+      }
+
+      if (!program_path) {
+	    program_path = g_utf16_to_utf8(path_pfx, -1, NULL, NULL, NULL);
+      }
+
+      if (GetSystemDirectory(path_pfx, MAX_PATH) == 0) {
+	    return FALSE;
+      }
+
+      if (!system_path) {
+	    system_path = g_utf16_to_utf8(path_pfx, -1, NULL, NULL, NULL);
+      }
+
+      if (program_path && system_path)
+	    return TRUE;
+
+      return FALSE;      
+}
+
+/*
+ * Internally g_module_open uses LoadLibrary on Windows and returns an
+ * HMODULE cast to a GModule *. However there's no guarantee that this
+ * will always be the case, so we call LoadLibrary and g_module_open
+ * separately.
+ */
+
+void *
+ws_load_library(gchar *library_name) {
+      gchar   *full_path;
+      wchar_t *full_path_w;
+      HMODULE  dll_h;
+
+      if (!init_dll_load_paths() || !library_name)
+	    return NULL;
+
+      /* First try the program directory */
+      full_path = g_module_build_path(program_path, library_name);
+      full_path_w = g_utf8_to_utf16(full_path, -1, NULL, NULL, NULL);
+      
+      if (full_path && full_path_w) {
+	    dll_h = LoadLibraryW(full_path_w);
+	    if (dll_h) {
+		  g_free(full_path);
+		  g_free(full_path_w);
+		  return dll_h;
+	    }
+      }
+
+      /* Next try the system directory */
+      full_path = g_module_build_path(system_path, library_name);
+      full_path_w = g_utf8_to_utf16(full_path, -1, NULL, NULL, NULL);
+
+      if (full_path && full_path_w) {
+	    dll_h = LoadLibraryW(full_path_w);
+	    if (dll_h) {
+		  g_free(full_path);
+		  g_free(full_path_w);
+		  return dll_h;
+	    }
+      }
+
+      return NULL;
+}
+
+GModule *
+ws_module_open(gchar *module_name, GModuleFlags flags) {
+      gchar   *full_path;
+      GModule *mod;
+
+      if (!init_dll_load_paths() || !module_name)
+	    return NULL;
+
+      /* First try the program directory */
+      full_path = g_module_build_path(program_path, module_name);
+      
+      if (full_path) {
+	    mod = g_module_open(full_path, flags);
+	    if (mod) {
+		  g_free(full_path);
+		  return mod;
+	    }
+      }
+
+      /* Next try the system directory */
+      full_path = g_module_build_path(system_path, module_name);
+      
+      if (full_path) {
+	    mod = g_module_open(full_path, flags);
+	    if (mod) {
+		  g_free(full_path);
+		  return mod;
+	    }
+      }
+
+      return NULL;
+}
\ No newline at end of file
diff --git a/wsutil/file_util.h b/wsutil/file_util.h
index e7ee04259f..bf5689905a 100644
--- a/wsutil/file_util.h
+++ b/wsutil/file_util.h
@@ -33,6 +33,7 @@ extern "C" {
 
 #ifdef _WIN32
 #include <io.h>
+#include <gmodule.h>
 #endif
 
 #ifdef HAVE_SYS_STAT_H
@@ -114,6 +115,25 @@ extern FILE * ws_stdio_freopen (const gchar *filename, const gchar *mode, FILE *
 #define ws_dir_rewind			g_dir_rewind
 #define ws_dir_close			g_dir_close
 
+/* DLL loading */
+
+/** Load a DLL using LoadLibrary.
+ * Only the system and program directories are searched.
+ *
+ * @param library_name The name of the DLL.
+ * @return A handle to the DLL if found, NULL on failure.
+ */
+
+void *ws_load_library(gchar *library_name);
+/** Load a DLL using g_module_open.
+ * Only the system and program directories are searched.
+ *
+ * @param module_name The name of the DLL.
+ * @param flags Flags to be passed to g_module_open.
+ * @return A handle to the DLL if found, NULL on failure.
+ */
+GModule *ws_module_open(gchar *module_name, GModuleFlags flags);
+
 /* XXX - remove include "dirent.h" */
 /* XXX - remove include "direct.h" */
 /* XXX - remove include "sys/stat.h" */
diff --git a/wsutil/libwsutil.def b/wsutil/libwsutil.def
index 2cbe0852b0..a0cafe95fc 100644
--- a/wsutil/libwsutil.def
+++ b/wsutil/libwsutil.def
@@ -18,6 +18,8 @@ ws_stdio_remove
 ws_stdio_rename
 ws_stdio_stat
 ws_stdio_unlink
+ws_load_library
+ws_module_open
 
 ; inet_aton.c
 inet_aton