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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/common/important_file_writer.h"
#include <stdio.h>
#include <string>
#include "base/bind.h"
#include "base/file_path.h"
#include "base/file_util.h"
#include "base/logging.h"
#include "base/message_loop_proxy.h"
#include "base/metrics/histogram.h"
#include "base/string_number_conversions.h"
#include "base/threading/thread.h"
#include "base/time.h"
using base::TimeDelta;
namespace {
const int kDefaultCommitIntervalMs = 10000;
enum TempFileFailure {
FAILED_CREATING,
FAILED_OPENING,
FAILED_CLOSING,
FAILED_WRITING,
FAILED_RENAMING,
TEMP_FILE_FAILURE_MAX
};
void LogFailure(const FilePath& path, TempFileFailure failure_code,
const std::string& message) {
UMA_HISTOGRAM_ENUMERATION("ImportantFile.TempFileFailures", failure_code,
TEMP_FILE_FAILURE_MAX);
DPLOG(WARNING) << "temp file failure: " << path.value()
<< " : " << message;
}
void WriteToDiskTask(const FilePath& path, const std::string& data) {
// Write the data to a temp file then rename to avoid data loss if we crash
// while writing the file. Ensure that the temp file is on the same volume
// as target file, so it can be moved in one step, and that the temp file
// is securely created.
FilePath tmp_file_path;
if (!file_util::CreateTemporaryFileInDir(path.DirName(), &tmp_file_path)) {
LogFailure(path, FAILED_CREATING, "could not create temporary file");
return;
}
int flags = base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_WRITE;
base::PlatformFile tmp_file =
base::CreatePlatformFile(tmp_file_path, flags, NULL, NULL);
if (tmp_file == base::kInvalidPlatformFileValue) {
LogFailure(path, FAILED_OPENING, "could not open temporary file");
return;
}
// If this happens in the wild something really bad is going on.
CHECK_LE(data.length(), static_cast<size_t>(kint32max));
int bytes_written = base::WritePlatformFile(
tmp_file, 0, data.data(), static_cast<int>(data.length()));
base::FlushPlatformFile(tmp_file); // Ignore return value.
if (!base::ClosePlatformFile(tmp_file)) {
LogFailure(path, FAILED_CLOSING, "failed to close temporary file");
file_util::Delete(tmp_file_path, false);
return;
}
if (bytes_written < static_cast<int>(data.length())) {
LogFailure(path, FAILED_WRITING, "error writing, bytes_written=" +
base::IntToString(bytes_written));
file_util::Delete(tmp_file_path, false);
return;
}
if (!file_util::ReplaceFile(tmp_file_path, path)) {
LogFailure(path, FAILED_RENAMING, "could not rename temporary file");
file_util::Delete(tmp_file_path, false);
return;
}
}
} // namespace
ImportantFileWriter::ImportantFileWriter(
const FilePath& path, base::MessageLoopProxy* file_message_loop_proxy)
: path_(path),
file_message_loop_proxy_(file_message_loop_proxy),
serializer_(NULL),
commit_interval_(TimeDelta::FromMilliseconds(
kDefaultCommitIntervalMs)) {
DCHECK(CalledOnValidThread());
DCHECK(file_message_loop_proxy_.get());
}
ImportantFileWriter::~ImportantFileWriter() {
// We're usually a member variable of some other object, which also tends
// to be our serializer. It may not be safe to call back to the parent object
// being destructed.
DCHECK(!HasPendingWrite());
}
bool ImportantFileWriter::HasPendingWrite() const {
DCHECK(CalledOnValidThread());
return timer_.IsRunning();
}
void ImportantFileWriter::WriteNow(const std::string& data) {
DCHECK(CalledOnValidThread());
if (data.length() > static_cast<size_t>(kint32max)) {
NOTREACHED();
return;
}
if (HasPendingWrite())
timer_.Stop();
if (!file_message_loop_proxy_->PostTask(
FROM_HERE, base::Bind(&WriteToDiskTask, path_, data))) {
// Posting the task to background message loop is not expected
// to fail, but if it does, avoid losing data and just hit the disk
// on the current thread.
NOTREACHED();
WriteToDiskTask(path_, data);
}
}
void ImportantFileWriter::ScheduleWrite(DataSerializer* serializer) {
DCHECK(CalledOnValidThread());
DCHECK(serializer);
serializer_ = serializer;
if (!timer_.IsRunning()) {
timer_.Start(FROM_HERE, commit_interval_, this,
&ImportantFileWriter::DoScheduledWrite);
}
}
void ImportantFileWriter::DoScheduledWrite() {
DCHECK(serializer_);
std::string data;
if (serializer_->SerializeData(&data)) {
WriteNow(data);
} else {
DLOG(WARNING) << "failed to serialize data to be saved in "
<< path_.value();
}
serializer_ = NULL;
}
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