win32: add tmpfile() replacement

The Windows version of tmpfile is actually pretty broken. It tries to
create the file in the root directory of the current drive, which means
on Vista and up, it normally fails due to insufficient permissions.
Replace it with a version that uses GetTempPath.

Also remove the Windows-specific note about automatic deletion of the
cache file. FILE_FLAG_DELETE_ON_CLOSE is available in NT, and it should
be pretty reliable.

2 files changed, 37 insertions, 0 deletions

diff --git a/osdep/io.c b/osdep/io.c
index e0caa56f79..819cdcbf69 100644
--- a/osdep/io.c
+++ b/osdep/io.c
@@ -310,6 +310,41 @@ int mp_mkdir(const char *path, int mode)
     return res;
 }
 
+FILE *mp_tmpfile(void)
+{
+    // Reserve a file name in the format %TMP%\mpvXXXX.TMP
+    wchar_t tmp_path[MAX_PATH + 1];
+    if (!GetTempPathW(MAX_PATH + 1, tmp_path))
+        return NULL;
+    wchar_t tmp_name[MAX_PATH + 1];
+    if (!GetTempFileNameW(tmp_path, L"mpv", 0, tmp_name))
+        return NULL;
+
+    // Create the file. FILE_ATTRIBUTE_TEMPORARY indicates the file will be
+    // short-lived. Windows should avoid flushing it to disk while there is
+    // sufficient cache.
+    HANDLE file = CreateFileW(tmp_name, GENERIC_READ | GENERIC_WRITE | DELETE,
+        FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, CREATE_ALWAYS,
+        FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, NULL);
+    if (file == INVALID_HANDLE_VALUE) {
+        DeleteFileW(tmp_name);
+        return NULL;
+    }
+
+    int fd = _open_osfhandle((intptr_t)file, 0);
+    if (fd < 0) {
+        CloseHandle(file);
+        return NULL;
+    }
+    FILE *fp = fdopen(fd, "w+b");
+    if (!fp) {
+        close(fd);
+        return NULL;
+    }
+
+    return fp;
+}
+
 static char **utf8_environ;
 static void *utf8_environ_ctx;
 
diff --git a/osdep/io.h b/osdep/io.h
index 306e2ac6ec..ae3cdc1802 100644
--- a/osdep/io.h
+++ b/osdep/io.h
@@ -75,6 +75,7 @@ DIR *mp_opendir(const char *path);
 struct dirent *mp_readdir(DIR *dir);
 int mp_closedir(DIR *dir);
 int mp_mkdir(const char *path, int mode);
+FILE *mp_tmpfile(void);
 char *mp_getenv(const char *name);
 
 typedef struct {
@@ -101,6 +102,7 @@ void mp_globfree(mp_glob_t *pglob);
 #define readdir(...) mp_readdir(__VA_ARGS__)
 #define closedir(...) mp_closedir(__VA_ARGS__)
 #define mkdir(...) mp_mkdir(__VA_ARGS__)
+#define tmpfile(...) mp_tmpfile(__VA_ARGS__)
 #define getenv(...) mp_getenv(__VA_ARGS__)
 
 #ifndef GLOB_NOMATCH