ImportantFileWriter

Introducing a class for writing important files, preventing their corruption during writing.

Switched PrefService to use it. Other classes will be switched in future changesets.

TEST=This may affect things using preferences. Make sure that changes in preferences don't get lost, and that you don't get excessive disk activity when changing preferences.

http://crbug.com/10618

Review URL: http://codereview.chromium.org/83001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@14717 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 29 insertions, 24 deletions

diff --git a/base/file_util.cc b/base/file_util.cc
index f7a0411..8eec3ac 100644
--- a/base/file_util.cc
+++ b/base/file_util.cc
@@ -188,6 +188,14 @@ bool ReadFileToString(const FilePath& path, std::string* contents) {
   return true;
 }
 
+FILE* CreateAndOpenTemporaryFile(FilePath* path) {
+  FilePath directory;
+  if (!GetTempDir(&directory))
+    return false;
+
+  return CreateAndOpenTemporaryFileInDir(directory, path);
+}
+
 bool GetFileSize(const FilePath& file_path, int64* file_size) {
   FileInfo info;
   if (!GetFileInfo(file_path, &info))
diff --git a/base/file_util.h b/base/file_util.h
index 489cbcc..47254ab 100644
--- a/base/file_util.h
+++ b/base/file_util.h
@@ -296,6 +296,9 @@ FILE* CreateAndOpenTemporaryFile(FilePath* path);
 // Like above but for shmem files.  Only useful for POSIX.
 FILE* CreateAndOpenTemporaryShmemFile(FilePath* path);
 
+// Similar to CreateAndOpenTemporaryFile, but the file is created in |dir|.
+FILE* CreateAndOpenTemporaryFileInDir(const FilePath& dir, FilePath* path);
+
 // Same as CreateTemporaryFileName but the file is created in |dir|.
 bool CreateTemporaryFileNameInDir(const std::wstring& dir,
                                   std::wstring* temp_file);
diff --git a/base/file_util_posix.cc b/base/file_util_posix.cc
index f218460..1835d3a 100644
--- a/base/file_util_posix.cc
+++ b/base/file_util_posix.cc
@@ -369,30 +369,20 @@ bool CreateTemporaryFileName(FilePath* path) {
   return true;
 }
 
-FILE* CreateAndOpenTemporaryFile(FilePath* path) {
-  FilePath directory;
-  if (!GetTempDir(&directory))
-    return false;
-
-  int fd = CreateAndOpenFdForTemporaryFile(directory, path);
-  if (fd < 0)
-    return NULL;
-
-  FILE *fp = fdopen(fd, "a+");
-  return fp;
-}
-
 FILE* CreateAndOpenTemporaryShmemFile(FilePath* path) {
   FilePath directory;
   if (!GetShmemTempDir(&directory))
     return false;
 
-  int fd = CreateAndOpenFdForTemporaryFile(directory, path);
+  return CreateAndOpenTemporaryFileInDir(directory, path);
+}
+
+FILE* CreateAndOpenTemporaryFileInDir(const FilePath& dir, FilePath* path) {
+  int fd = CreateAndOpenFdForTemporaryFile(dir, path);
   if (fd < 0)
     return NULL;
 
-  FILE *fp = fdopen(fd, "a+");
-  return fp;
+  return fdopen(fd, "a+");
 }
 
 bool CreateTemporaryFileNameInDir(const std::wstring& dir,
diff --git a/base/file_util_win.cc b/base/file_util_win.cc
index 8b3d4f5..8964fbf 100644
--- a/base/file_util_win.cc
+++ b/base/file_util_win.cc
@@ -446,20 +446,24 @@ bool CreateTemporaryFileName(FilePath* path) {
   return false;
 }
 
+FILE* CreateAndOpenTemporaryShmemFile(FilePath* path) {
+  return CreateAndOpenTemporaryFile(path);
+}
+
 // On POSIX we have semantics to create and open a temporary file
 // atomically.
 // TODO(jrg): is there equivalent call to use on Windows instead of
 // going 2-step?
-FILE* CreateAndOpenTemporaryFile(FilePath* path) {
-
-  if (!CreateTemporaryFileName(path)) {
+FILE* CreateAndOpenTemporaryFileInDir(const FilePath& dir, FilePath* path) {
+  std::wstring wstring_path;
+  if (!CreateTemporaryFileNameInDir(dir.value(), &wstring_path)) {
     return NULL;
   }
-  return OpenFile(*path, "w+");
-}
-
-FILE* CreateAndOpenTemporaryShmemFile(FilePath* path) {
-  return CreateAndOpenTemporaryFile(path);
+  *path = FilePath(wstring_path);
+  // Open file in binary mode, to avoid problems with fwrite. On Windows
+  // it replaces \n's with \r\n's, which may surprise you.
+  // Reference: http://msdn.microsoft.com/en-us/library/h9t88zwz(VS.71).aspx
+  return OpenFile(*path, "wb+");
 }
 
 bool CreateTemporaryFileNameInDir(const std::wstring& dir,