FFmpeg
w32dlfcn.h
Go to the documentation of this file.
1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #ifndef COMPAT_W32DLFCN_H
20 #define COMPAT_W32DLFCN_H
21 
22 #ifdef _WIN32
23 #include <stdint.h>
24 
25 #include <windows.h>
26 
27 #include "config.h"
28 #include "libavutil/macros.h"
30 
31 static inline wchar_t *get_module_filename(HMODULE module)
32 {
33  wchar_t *path = NULL, *new_path;
34  DWORD path_size = 0, path_len;
35 
36  do {
37  path_size = path_size ? FFMIN(2 * path_size, INT16_MAX + 1) : MAX_PATH;
38  new_path = av_realloc_array(path, path_size, sizeof *path);
39  if (!new_path) {
40  av_free(path);
41  return NULL;
42  }
43  path = new_path;
44  // Returns path_size in case of insufficient buffer.
45  // Whether the error is set or not and whether the output
46  // is null-terminated or not depends on the version of Windows.
47  path_len = GetModuleFileNameW(module, path, path_size);
48  } while (path_len && path_size <= INT16_MAX && path_size <= path_len);
49 
50  if (!path_len) {
51  av_free(path);
52  return NULL;
53  }
54  return path;
55 }
56 
57 /**
58  * Safe function used to open dynamic libs. This attempts to improve program security
59  * by removing the current directory from the dll search path. Only dll's found in the
60  * executable or system directory are allowed to be loaded.
61  * @param name The dynamic lib name.
62  * @return A handle to the opened lib.
63  */
64 static inline HMODULE win32_dlopen(const char *name)
65 {
66  wchar_t *name_w;
67  HMODULE module = NULL;
68  if (utf8towchar(name, &name_w))
69  name_w = NULL;
70 #if _WIN32_WINNT < 0x0602
71  // On Win7 and earlier we check if KB2533623 is available
72  if (!GetProcAddress(GetModuleHandleW(L"kernel32.dll"), "SetDefaultDllDirectories")) {
73  wchar_t *path = NULL, *new_path;
74  DWORD pathlen, pathsize, namelen;
75  if (!name_w)
76  goto exit;
77  namelen = wcslen(name_w);
78  // Try local directory first
79  path = get_module_filename(NULL);
80  if (!path)
81  goto exit;
82  new_path = wcsrchr(path, '\\');
83  if (!new_path)
84  goto exit;
85  pathlen = new_path - path;
86  pathsize = pathlen + namelen + 2;
87  new_path = av_realloc_array(path, pathsize, sizeof *path);
88  if (!new_path)
89  goto exit;
90  path = new_path;
91  wcscpy(path + pathlen + 1, name_w);
92  module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
93  if (module == NULL) {
94  // Next try System32 directory
95  pathlen = GetSystemDirectoryW(path, pathsize);
96  if (!pathlen)
97  goto exit;
98  // Buffer is not enough in two cases:
99  // 1. system directory + \ + module name
100  // 2. system directory even without the module name.
101  if (pathlen + namelen + 2 > pathsize) {
102  pathsize = pathlen + namelen + 2;
103  new_path = av_realloc_array(path, pathsize, sizeof *path);
104  if (!new_path)
105  goto exit;
106  path = new_path;
107  // Query again to handle the case #2.
108  pathlen = GetSystemDirectoryW(path, pathsize);
109  if (!pathlen)
110  goto exit;
111  }
112  path[pathlen] = L'\\';
113  wcscpy(path + pathlen + 1, name_w);
114  module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
115  }
116 exit:
117  av_free(path);
118  av_free(name_w);
119  return module;
120  }
121 #endif
122 #ifndef LOAD_LIBRARY_SEARCH_APPLICATION_DIR
123 # define LOAD_LIBRARY_SEARCH_APPLICATION_DIR 0x00000200
124 #endif
125 #ifndef LOAD_LIBRARY_SEARCH_SYSTEM32
126 # define LOAD_LIBRARY_SEARCH_SYSTEM32 0x00000800
127 #endif
128 #if HAVE_WINRT
129  if (!name_w)
130  return NULL;
131  module = LoadPackagedLibrary(name_w, 0);
132 #else
133 #define LOAD_FLAGS (LOAD_LIBRARY_SEARCH_APPLICATION_DIR | LOAD_LIBRARY_SEARCH_SYSTEM32)
134  /* filename may be be in CP_ACP */
135  if (!name_w)
136  return LoadLibraryExA(name, NULL, LOAD_FLAGS);
137  module = LoadLibraryExW(name_w, NULL, LOAD_FLAGS);
138 #undef LOAD_FLAGS
139 #endif
140  av_free(name_w);
141  return module;
142 }
143 #define dlopen(name, flags) win32_dlopen(name)
144 #define dlclose FreeLibrary
145 #define dlsym GetProcAddress
146 #else
147 #include <dlfcn.h>
148 #endif
149 
150 #endif /* COMPAT_W32DLFCN_H */
wchar_filename.h
name
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default minimum maximum flags name is the option name
Definition: writing_filters.txt:88
macros.h
av_realloc_array
void * av_realloc_array(void *ptr, size_t nmemb, size_t size)
Definition: mem.c:225
NULL
#define NULL
Definition: coverity.c:32
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
L
#define L(x)
Definition: vpx_arith.h:36
av_free
#define av_free(p)
Definition: tableprint_vlc.h:33