Re: [FFmpeg-devel] [PATCH] Long path support for Windows (fixes #8885)

[nihil-admirari@tutanota.com]

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Let's try once again with .diff extension.

Feb 13, 2022, 19:48 by nihil-admirari@tutanota.com:

> Previous patch got corrupted with lots of unbreakable spaces C2 A0, so it does not apply: > https://patchwork.ffmpeg.org/project/ffmpeg/patch/Mvn2TLP--3-2@tutanota.com/> . Let's retry with an attachment.
>

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From d328777fe84166c78124dc27708596dd830a99e2 Mon Sep 17 00:00:00 2001
From: nihil-admirari <50202386+nihil-admirari@users.noreply.github.com>
Date: Sun, 13 Feb 2022 13:43:56 +0300
Subject: [PATCH] Long path support for Windows (fixes #8885)

Long path support is enabled by adding a manifest to all of fftools.
MAX_PATH-sized buffers are replaced with dynamically sized ones.

Signed-off-by: nihil-admirari <50202386+nihil-admirari@users.noreply.github.com>
---
 compat/w32dlfcn.h                | 61 +++++++++++++++++++++++++++-----
 fftools/Makefile                 |  5 +++
 fftools/cmdutils.c               | 31 ++++++++++++----
 fftools/long_paths_utf8.manifest | 12 +++++++
 fftools/long_paths_utf8.rc       |  3 ++
 libavformat/avisynth.c           | 10 +++---
 libavutil/wchar_filename.h       | 37 +++++++++++++++++++
 7 files changed, 139 insertions(+), 20 deletions(-)
 create mode 100644 fftools/long_paths_utf8.manifest
 create mode 100644 fftools/long_paths_utf8.rc

diff --git a/compat/w32dlfcn.h b/compat/w32dlfcn.h
index 52a94ef..ba2330a 100644
--- a/compat/w32dlfcn.h
+++ b/compat/w32dlfcn.h
@@ -25,6 +25,30 @@
 #if (_WIN32_WINNT < 0x0602) || HAVE_WINRT
 #include "libavutil/wchar_filename.h"
 #endif
+
+static inline wchar_t *get_module_filename(const HMODULE module)
+{
+    wchar_t *path = NULL;
+    int path_size = 0, path_len = 0;
+
+    do {
+        path_size = path_size ? 1.5 * path_size : MAX_PATH;
+        wchar_t *new_path = av_realloc_array(path, path_size, sizeof *path);
+        if (!new_path) {
+            av_free(path);
+            return NULL;
+        }
+        path = new_path;
+        path_len = GetModuleFileNameW(module, path, path_size);
+    } while (path_len && path_size <= 32768 && path_size <= path_len);
+
+    if (!path_len) {
+        av_free(path);
+        return NULL;
+    }
+    return path;
+}
+
 /**
  * Safe function used to open dynamic libs. This attempts to improve program security
  * by removing the current directory from the dll search path. Only dll's found in the
@@ -38,24 +62,43 @@ static inline HMODULE win32_dlopen(const char *name)
     // Need to check if KB2533623 is available
     if (!GetProcAddress(GetModuleHandleW(L"kernel32.dll"), "SetDefaultDllDirectories")) {
         HMODULE module = NULL;
-        wchar_t *path = NULL, *name_w = NULL;
-        DWORD pathlen;
+        wchar_t *path = NULL, *new_path = NULL, *name_w = NULL;
+        DWORD pathlen, pathsize, namelen;
         if (utf8towchar(name, &name_w))
             goto exit;
-        path = (wchar_t *)av_calloc(MAX_PATH, sizeof(wchar_t));
+        namelen = wcslen(name_w);
         // Try local directory first
-        pathlen = GetModuleFileNameW(NULL, path, MAX_PATH);
-        pathlen = wcsrchr(path, '\\') - path;
-        if (pathlen == 0 || pathlen + wcslen(name_w) + 2 > MAX_PATH)
+        path = get_module_filename(NULL);
+        if (!path)
+            goto exit;
+        new_path = wcsrchr(path, '\\');
+        if (!new_path)
+            goto exit;
+        pathlen = new_path - path;
+        pathsize = pathlen + namelen + 2;
+        new_path = av_realloc_array(path, pathsize, sizeof *path);
+        if (!new_path)
             goto exit;
-        path[pathlen] = '\\';
+        path = new_path;
         wcscpy(path + pathlen + 1, name_w);
         module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
         if (module == NULL) {
             // Next try System32 directory
-            pathlen = GetSystemDirectoryW(path, MAX_PATH);
-            if (pathlen == 0 || pathlen + wcslen(name_w) + 2 > MAX_PATH)
+            pathlen = GetSystemDirectoryW(path, pathsize);
+            if (!pathlen)
                 goto exit;
+            if (pathlen + namelen + 2 > pathsize) {
+                pathsize = pathlen + namelen + 2;
+                new_path = av_realloc_array(path, pathsize, sizeof *path);
+                if (!new_path)
+                    goto exit;
+                path = new_path;
+                // The buffer might have been not enough for system directory
+                // in the first place.
+                pathlen = GetSystemDirectoryW(path, pathsize);
+                if (!pathlen)
+                    goto exit;
+            }
             path[pathlen] = '\\';
             wcscpy(path + pathlen + 1, name_w);
             module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
diff --git a/fftools/Makefile b/fftools/Makefile
index da42078..53438b6 100644
--- a/fftools/Makefile
+++ b/fftools/Makefile
@@ -11,6 +11,11 @@ ALLAVPROGS_G = $(AVBASENAMES:%=%$(PROGSSUF)_g$(EXESUF))
 
 OBJS-ffmpeg                        += fftools/ffmpeg_opt.o fftools/ffmpeg_filter.o fftools/ffmpeg_hw.o
 
+# Windows resource files
+OBJS-ffmpeg-$(HAVE_GNU_WINDRES) += fftools/long_paths_utf8.o
+OBJS-ffplay-$(HAVE_GNU_WINDRES) += fftools/long_paths_utf8.o
+OBJS-ffprobe-$(HAVE_GNU_WINDRES) += fftools/long_paths_utf8.o
+
 define DOFFTOOL
 OBJS-$(1) += fftools/cmdutils.o fftools/$(1).o $(OBJS-$(1)-yes)
 $(1)$(PROGSSUF)_g$(EXESUF): $$(OBJS-$(1))
diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
index 4b50e15..ea78897 100644
--- a/fftools/cmdutils.c
+++ b/fftools/cmdutils.c
@@ -62,6 +62,7 @@
 #endif
 #ifdef _WIN32
 #include <windows.h>
+#include "compat/w32dlfcn.h"
 #endif
 
 static int init_report(const char *env);
@@ -2065,6 +2066,9 @@ FILE *get_preset_file(char *filename, size_t filename_size,
 {
     FILE *f = NULL;
     int i;
+#if HAVE_GETMODULEHANDLE && defined(_WIN32)
+    char *datadir = NULL;
+#endif
     const char *base[3] = { getenv("FFMPEG_DATADIR"),
                             getenv("HOME"),
                             FFMPEG_DATADIR, };
@@ -2074,19 +2078,31 @@ FILE *get_preset_file(char *filename, size_t filename_size,
         f = fopen(filename, "r");
     } else {
 #if HAVE_GETMODULEHANDLE && defined(_WIN32)
-        char datadir[MAX_PATH], *ls;
+        wchar_t *datadir_w = get_module_filename(NULL);
         base[2] = NULL;
 
-        if (GetModuleFileNameA(GetModuleHandleA(NULL), datadir, sizeof(datadir) - 1))
+        if (wchartoansi(datadir_w, &datadir))
+            datadir = NULL;
+        av_free(datadir_w);
+
+        if (datadir)
         {
-            for (ls = datadir; ls < datadir + strlen(datadir); ls++)
+            char *ls;
+            for (ls = datadir; *ls; ls++)
                 if (*ls == '\\') *ls = '/';
 
             if (ls = strrchr(datadir, '/'))
             {
-                *ls = 0;
-                strncat(datadir, "/ffpresets",  sizeof(datadir) - 1 - strlen(datadir));
-                base[2] = datadir;
+                const int datadir_len = ls - datadir;
+                const int desired_size = datadir_len + strlen("/ffpresets") + 1;
+                char *new_datadir = av_realloc_array(
+                    datadir, desired_size, sizeof *datadir);
+                if (new_datadir) {
+                    datadir = new_datadir;
+                    datadir[datadir_len] = 0;
+                    strncat(datadir, "/ffpresets",  desired_size - 1 - datadir_len);
+                    base[2] = datadir;
+                }
             }
         }
 #endif
@@ -2106,6 +2122,9 @@ FILE *get_preset_file(char *filename, size_t filename_size,
         }
     }
 
+#if HAVE_GETMODULEHANDLE && defined(_WIN32)
+    av_free(datadir);
+#endif
     return f;
 }
 
diff --git a/fftools/long_paths_utf8.manifest b/fftools/long_paths_utf8.manifest
new file mode 100644
index 0000000..d1ac1e4
--- /dev/null
+++ b/fftools/long_paths_utf8.manifest
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <assemblyIdentity type="win32" name="FFmpeg" version="1.0.0.0"/>
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings xmlns:ws2016="http://schemas.microsoft.com/SMI/2016/WindowsSettings"
+                     xmlns:ws2019="http://schemas.microsoft.com/SMI/2019/WindowsSettings">
+      <ws2016:longPathAware>true</ws2016:longPathAware>
+      <ws2019:activeCodePage>UTF-8</ws2019:activeCodePage>
+    </windowsSettings>
+  </application>
+</assembly>
diff --git a/fftools/long_paths_utf8.rc b/fftools/long_paths_utf8.rc
new file mode 100644
index 0000000..f33de76
--- /dev/null
+++ b/fftools/long_paths_utf8.rc
@@ -0,0 +1,3 @@
+#include <windows.h>
+
+CREATEPROCESS_MANIFEST_RESOURCE_ID RT_MANIFEST "long_paths_utf8.manifest"
diff --git a/libavformat/avisynth.c b/libavformat/avisynth.c
index 350ac6d..3738cb1 100644
--- a/libavformat/avisynth.c
+++ b/libavformat/avisynth.c
@@ -34,6 +34,7 @@
 /* Platform-specific directives. */
 #ifdef _WIN32
   #include "compat/w32dlfcn.h"
+  #include "libavutil/wchar_filename.h"
   #undef EXTERN_C
   #define AVISYNTH_LIB "avisynth"
 #else
@@ -572,8 +573,7 @@ static int avisynth_open_file(AVFormatContext *s)
     AVS_Value arg, val;
     int ret;
 #ifdef _WIN32
-    char filename_ansi[MAX_PATH * 4];
-    wchar_t filename_wc[MAX_PATH * 4];
+    char *filename_ansi = NULL;
 #endif
 
     if (ret = avisynth_context_create(s))
@@ -581,10 +581,10 @@ static int avisynth_open_file(AVFormatContext *s)
 
 #ifdef _WIN32
     /* Convert UTF-8 to ANSI code page */
-    MultiByteToWideChar(CP_UTF8, 0, s->url, -1, filename_wc, MAX_PATH * 4);
-    WideCharToMultiByte(CP_THREAD_ACP, 0, filename_wc, -1, filename_ansi,
-                        MAX_PATH * 4, NULL, NULL);
+    if (utf8toansi(s->url, &filename_ansi))
+        goto fail;
     arg = avs_new_value_string(filename_ansi);
+    av_free(filename_ansi);
 #else
     arg = avs_new_value_string(s->url);
 #endif
diff --git a/libavutil/wchar_filename.h b/libavutil/wchar_filename.h
index 90f0824..32260a4 100644
--- a/libavutil/wchar_filename.h
+++ b/libavutil/wchar_filename.h
@@ -40,6 +40,43 @@ static inline int utf8towchar(const char *filename_utf8, wchar_t **filename_w)
     MultiByteToWideChar(CP_UTF8, 0, filename_utf8, -1, *filename_w, num_chars);
     return 0;
 }
+
+av_warn_unused_result
+static inline int wchartoansi(const wchar_t *filename_w, char **filename)
+{
+    const int num_chars = WideCharToMultiByte(CP_THREAD_ACP, 0, filename_w, -1,
+                                              NULL, 0, NULL, NULL);
+    if (num_chars <= 0) {
+        *filename = NULL;
+        return 0;
+    }
+    *filename = (char *)av_calloc(num_chars, sizeof(char));
+    if (!*filename) {
+        errno = ENOMEM;
+        return -1;
+    }
+    WideCharToMultiByte(CP_THREAD_ACP, 0, filename_w, -1,
+                        *filename, num_chars, NULL, NULL);
+    return 0;
+}
+
+av_warn_unused_result
+static inline int utf8toansi(const char *filename_utf8, char **filename)
+{
+    wchar_t *filename_w = NULL;
+    int ret = -1;
+    if (utf8towchar(filename_utf8, &filename_w))
+        return -1;
+
+    if (!filename_w) {
+        *filename = NULL;
+        return 0;
+    }
+
+    ret = wchartoansi(filename_w, filename);
+    av_free(filename_w);
+    return ret;
+}
 #endif
 
 #endif /* AVUTIL_WCHAR_FILENAME_H */
-- 
2.32.0


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