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// Copyright (c) 2012 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/browser/sessions/session_backend.h"
#include <limits>
#include "base/file_util.h"
#include "base/memory/scoped_vector.h"
#include "base/metrics/histogram.h"
#include "base/threading/thread_restrictions.h"
#include "net/base/file_stream.h"
#include "net/base/net_errors.h"
using base::TimeTicks;
// File version number.
static const int32 kFileCurrentVersion = 1;
// The signature at the beginning of the file = SSNS (Sessions).
static const int32 kFileSignature = 0x53534E53;
namespace {
// The file header is the first bytes written to the file,
// and is used to identify the file as one written by us.
struct FileHeader {
int32 signature;
int32 version;
};
// SessionFileReader ----------------------------------------------------------
// SessionFileReader is responsible for reading the set of SessionCommands that
// describe a Session back from a file. SessionFileRead does minimal error
// checking on the file (pretty much only that the header is valid).
class SessionFileReader {
public:
typedef SessionCommand::id_type id_type;
typedef SessionCommand::size_type size_type;
explicit SessionFileReader(const FilePath& path)
: errored_(false),
buffer_(SessionBackend::kFileReadBufferSize, 0),
buffer_position_(0),
available_count_(0) {
file_.reset(new net::FileStream(NULL));
if (file_util::PathExists(path))
file_->OpenSync(path,
base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ);
}
// Reads the contents of the file specified in the constructor, returning
// true on success. It is up to the caller to free all SessionCommands
// added to commands.
bool Read(BaseSessionService::SessionType type,
std::vector<SessionCommand*>* commands);
private:
// Reads a single command, returning it. A return value of NULL indicates
// either there are no commands, or there was an error. Use errored_ to
// distinguish the two. If NULL is returned, and there is no error, it means
// the end of file was successfully reached.
SessionCommand* ReadCommand();
// Shifts the unused portion of buffer_ to the beginning and fills the
// remaining portion with data from the file. Returns false if the buffer
// couldn't be filled. A return value of false only signals an error if
// errored_ is set to true.
bool FillBuffer();
// Whether an error condition has been detected (
bool errored_;
// As we read from the file, data goes here.
std::string buffer_;
// The file.
scoped_ptr<net::FileStream> file_;
// Position in buffer_ of the data.
size_t buffer_position_;
// Number of available bytes; relative to buffer_position_.
size_t available_count_;
DISALLOW_COPY_AND_ASSIGN(SessionFileReader);
};
bool SessionFileReader::Read(BaseSessionService::SessionType type,
std::vector<SessionCommand*>* commands) {
if (!file_->IsOpen())
return false;
FileHeader header;
int read_count;
TimeTicks start_time = TimeTicks::Now();
read_count = file_->ReadUntilComplete(reinterpret_cast<char*>(&header),
sizeof(header));
if (read_count != sizeof(header) || header.signature != kFileSignature ||
header.version != kFileCurrentVersion)
return false;
ScopedVector<SessionCommand> read_commands;
SessionCommand* command;
while ((command = ReadCommand()) && !errored_)
read_commands.push_back(command);
if (!errored_)
read_commands.swap(*commands);
if (type == BaseSessionService::TAB_RESTORE) {
UMA_HISTOGRAM_TIMES("TabRestore.read_session_file_time",
TimeTicks::Now() - start_time);
} else {
UMA_HISTOGRAM_TIMES("SessionRestore.read_session_file_time",
TimeTicks::Now() - start_time);
}
return !errored_;
}
SessionCommand* SessionFileReader::ReadCommand() {
// Make sure there is enough in the buffer for the size of the next command.
if (available_count_ < sizeof(size_type)) {
if (!FillBuffer())
return NULL;
if (available_count_ < sizeof(size_type)) {
VLOG(1) << "SessionFileReader::ReadCommand, file incomplete";
// Still couldn't read a valid size for the command, assume write was
// incomplete and return NULL.
return NULL;
}
}
// Get the size of the command.
size_type command_size;
memcpy(&command_size, &(buffer_[buffer_position_]), sizeof(command_size));
buffer_position_ += sizeof(command_size);
available_count_ -= sizeof(command_size);
if (command_size == 0) {
VLOG(1) << "SessionFileReader::ReadCommand, empty command";
// Empty command. Shouldn't happen if write was successful, fail.
return NULL;
}
// Make sure buffer has the complete contents of the command.
if (command_size > available_count_) {
if (command_size > buffer_.size())
buffer_.resize((command_size / 1024 + 1) * 1024, 0);
if (!FillBuffer() || command_size > available_count_) {
// Again, assume the file was ok, and just the last chunk was lost.
VLOG(1) << "SessionFileReader::ReadCommand, last chunk lost";
return NULL;
}
}
const id_type command_id = buffer_[buffer_position_];
// NOTE: command_size includes the size of the id, which is not part of
// the contents of the SessionCommand.
SessionCommand* command =
new SessionCommand(command_id, command_size - sizeof(id_type));
if (command_size > sizeof(id_type)) {
memcpy(command->contents(),
&(buffer_[buffer_position_ + sizeof(id_type)]),
command_size - sizeof(id_type));
}
buffer_position_ += command_size;
available_count_ -= command_size;
return command;
}
bool SessionFileReader::FillBuffer() {
if (available_count_ > 0 && buffer_position_ > 0) {
// Shift buffer to beginning.
memmove(&(buffer_[0]), &(buffer_[buffer_position_]), available_count_);
}
buffer_position_ = 0;
DCHECK(buffer_position_ + available_count_ < buffer_.size());
int to_read = static_cast<int>(buffer_.size() - available_count_);
int read_count = file_->ReadUntilComplete(&(buffer_[available_count_]),
to_read);
if (read_count < 0) {
errored_ = true;
return false;
}
if (read_count == 0)
return false;
available_count_ += read_count;
return true;
}
} // namespace
// SessionBackend -------------------------------------------------------------
// File names (current and previous) for a type of TAB.
static const char* kCurrentTabSessionFileName = "Current Tabs";
static const char* kLastTabSessionFileName = "Last Tabs";
// File names (current and previous) for a type of SESSION.
static const char* kCurrentSessionFileName = "Current Session";
static const char* kLastSessionFileName = "Last Session";
// static
const int SessionBackend::kFileReadBufferSize = 1024;
SessionBackend::SessionBackend(BaseSessionService::SessionType type,
const FilePath& path_to_dir)
: type_(type),
path_to_dir_(path_to_dir),
last_session_valid_(false),
inited_(false),
empty_file_(true) {
// NOTE: this is invoked on the main thread, don't do file access here.
}
void SessionBackend::Init() {
if (inited_)
return;
inited_ = true;
// Create the directory for session info.
file_util::CreateDirectory(path_to_dir_);
MoveCurrentSessionToLastSession();
}
void SessionBackend::AppendCommands(
std::vector<SessionCommand*>* commands,
bool reset_first) {
Init();
// Make sure and check current_session_file_, if opening the file failed
// current_session_file_ will be NULL.
if ((reset_first && !empty_file_) || !current_session_file_.get() ||
!current_session_file_->IsOpen()) {
ResetFile();
}
// Need to check current_session_file_ again, ResetFile may fail.
if (current_session_file_.get() && current_session_file_->IsOpen() &&
!AppendCommandsToFile(current_session_file_.get(), *commands)) {
current_session_file_.reset(NULL);
}
empty_file_ = false;
STLDeleteElements(commands);
delete commands;
}
void SessionBackend::ReadLastSessionCommands(
const CancelableTaskTracker::IsCanceledCallback& is_canceled,
const BaseSessionService::InternalGetCommandsCallback& callback) {
if (is_canceled.Run())
return;
Init();
ScopedVector<SessionCommand> commands;
ReadLastSessionCommandsImpl(&(commands.get()));
callback.Run(commands.Pass());
}
bool SessionBackend::ReadLastSessionCommandsImpl(
std::vector<SessionCommand*>* commands) {
Init();
SessionFileReader file_reader(GetLastSessionPath());
return file_reader.Read(type_, commands);
}
void SessionBackend::DeleteLastSession() {
Init();
file_util::Delete(GetLastSessionPath(), false);
}
void SessionBackend::MoveCurrentSessionToLastSession() {
Init();
current_session_file_.reset(NULL);
const FilePath current_session_path = GetCurrentSessionPath();
const FilePath last_session_path = GetLastSessionPath();
if (file_util::PathExists(last_session_path))
file_util::Delete(last_session_path, false);
if (file_util::PathExists(current_session_path)) {
int64 file_size;
if (file_util::GetFileSize(current_session_path, &file_size)) {
if (type_ == BaseSessionService::TAB_RESTORE) {
UMA_HISTOGRAM_COUNTS("TabRestore.last_session_file_size",
static_cast<int>(file_size / 1024));
} else {
UMA_HISTOGRAM_COUNTS("SessionRestore.last_session_file_size",
static_cast<int>(file_size / 1024));
}
}
last_session_valid_ = file_util::Move(current_session_path,
last_session_path);
}
if (file_util::PathExists(current_session_path))
file_util::Delete(current_session_path, false);
// Create and open the file for the current session.
ResetFile();
}
bool SessionBackend::ReadCurrentSessionCommandsImpl(
std::vector<SessionCommand*>* commands) {
Init();
SessionFileReader file_reader(GetCurrentSessionPath());
return file_reader.Read(type_, commands);
}
bool SessionBackend::AppendCommandsToFile(net::FileStream* file,
const std::vector<SessionCommand*>& commands) {
for (std::vector<SessionCommand*>::const_iterator i = commands.begin();
i != commands.end(); ++i) {
int wrote;
const size_type content_size = static_cast<size_type>((*i)->size());
const size_type total_size = content_size + sizeof(id_type);
if (type_ == BaseSessionService::TAB_RESTORE)
UMA_HISTOGRAM_COUNTS("TabRestore.command_size", total_size);
else
UMA_HISTOGRAM_COUNTS("SessionRestore.command_size", total_size);
wrote = file->WriteSync(reinterpret_cast<const char*>(&total_size),
sizeof(total_size));
if (wrote != sizeof(total_size)) {
NOTREACHED() << "error writing";
return false;
}
id_type command_id = (*i)->id();
wrote = file->WriteSync(reinterpret_cast<char*>(&command_id),
sizeof(command_id));
if (wrote != sizeof(command_id)) {
NOTREACHED() << "error writing";
return false;
}
if (content_size > 0) {
wrote = file->WriteSync(reinterpret_cast<char*>((*i)->contents()),
content_size);
if (wrote != content_size) {
NOTREACHED() << "error writing";
return false;
}
}
}
file->FlushSync();
return true;
}
SessionBackend::~SessionBackend() {
if (current_session_file_.get()) {
// Destructor performs file IO because file is open in sync mode.
// crbug.com/112512.
base::ThreadRestrictions::ScopedAllowIO allow_io;
current_session_file_.reset();
}
}
void SessionBackend::ResetFile() {
DCHECK(inited_);
if (current_session_file_.get()) {
// File is already open, truncate it. We truncate instead of closing and
// reopening to avoid the possibility of scanners locking the file out
// from under us once we close it. If truncation fails, we'll try to
// recreate.
const int header_size = static_cast<int>(sizeof(FileHeader));
if (current_session_file_->Truncate(header_size) != header_size)
current_session_file_.reset(NULL);
}
if (!current_session_file_.get())
current_session_file_.reset(OpenAndWriteHeader(GetCurrentSessionPath()));
empty_file_ = true;
}
net::FileStream* SessionBackend::OpenAndWriteHeader(const FilePath& path) {
DCHECK(!path.empty());
scoped_ptr<net::FileStream> file(new net::FileStream(NULL));
if (file->OpenSync(path, base::PLATFORM_FILE_CREATE_ALWAYS |
base::PLATFORM_FILE_WRITE | base::PLATFORM_FILE_EXCLUSIVE_WRITE |
base::PLATFORM_FILE_EXCLUSIVE_READ) != net::OK)
return NULL;
FileHeader header;
header.signature = kFileSignature;
header.version = kFileCurrentVersion;
int wrote = file->WriteSync(reinterpret_cast<char*>(&header),
sizeof(header));
if (wrote != sizeof(header))
return NULL;
return file.release();
}
FilePath SessionBackend::GetLastSessionPath() {
FilePath path = path_to_dir_;
if (type_ == BaseSessionService::TAB_RESTORE)
path = path.AppendASCII(kLastTabSessionFileName);
else
path = path.AppendASCII(kLastSessionFileName);
return path;
}
FilePath SessionBackend::GetCurrentSessionPath() {
FilePath path = path_to_dir_;
if (type_ == BaseSessionService::TAB_RESTORE)
path = path.AppendASCII(kCurrentTabSessionFileName);
else
path = path.AppendASCII(kCurrentSessionFileName);
return path;
}
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