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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 "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/stl_util.h"
#include "net/disk_cache/flash/format.h"
#include "net/disk_cache/flash/log_structured_store.h"
#include "net/disk_cache/flash/segment.h"
#include "net/disk_cache/flash/storage.h"
namespace disk_cache {
LogStructuredStore::LogStructuredStore(Storage* storage)
: storage_(storage),
num_segments_(storage->size() / kFlashSegmentSize),
open_segments_(num_segments_),
write_index_(0),
current_entry_id_(-1),
current_entry_num_bytes_left_to_write_(0),
init_(false),
closed_(false) {
DCHECK(storage->size() % kFlashSegmentSize == 0);
}
LogStructuredStore::~LogStructuredStore() {
DCHECK(!init_ || closed_);
STLDeleteElements(&open_segments_);
}
bool LogStructuredStore::Init() {
DCHECK(!init_);
// TODO(agayev): Once we start persisting segment metadata to disk, we will
// start from where we left off during the last shutdown.
scoped_ptr<Segment> segment(new Segment(write_index_, false, storage_));
if (!segment->Init())
return false;
segment->AddUser();
open_segments_[write_index_] = segment.release();
init_ = true;
return true;
}
bool LogStructuredStore::Close() {
DCHECK(init_ && !closed_);
open_segments_[write_index_]->ReleaseUser();
if (!open_segments_[write_index_]->Close())
return false;
closed_ = true;
return true;
// TODO(agayev): persist metadata to disk.
}
bool LogStructuredStore::CreateEntry(int32 size, int32* id) {
DCHECK(init_ && !closed_);
DCHECK(current_entry_id_ == -1 && size <= disk_cache::kFlashSegmentFreeSpace);
// TODO(agayev): Avoid large entries from leaving the segments almost empty.
if (!open_segments_[write_index_]->CanHold(size)) {
if (!open_segments_[write_index_]->Close())
return false;
open_segments_[write_index_]->ReleaseUser();
if (open_segments_[write_index_]->HasNoUsers()) {
delete open_segments_[write_index_];
open_segments_[write_index_] = NULL;
}
write_index_ = GetNextSegmentIndex();
scoped_ptr<Segment> segment(new Segment(write_index_, false, storage_));
if (!segment->Init())
return false;
segment->AddUser();
open_segments_[write_index_] = segment.release();
}
*id = open_segments_[write_index_]->write_offset();
open_segments_[write_index_]->StoreOffset(*id);
current_entry_id_ = *id;
current_entry_num_bytes_left_to_write_ = size;
open_entries_.insert(current_entry_id_);
return true;
}
bool LogStructuredStore::WriteData(const void* buffer, int32 size) {
DCHECK(init_ && !closed_);
DCHECK(current_entry_id_ != -1 &&
size <= current_entry_num_bytes_left_to_write_);
if (open_segments_[write_index_]->WriteData(buffer, size)) {
current_entry_num_bytes_left_to_write_ -= size;
return true;
}
return false;
}
bool LogStructuredStore::OpenEntry(int32 id) {
DCHECK(init_ && !closed_);
if (open_entries_.find(id) != open_entries_.end())
return false;
// Segment is already open.
int32 index = id / disk_cache::kFlashSegmentSize;
if (open_segments_[index]) {
if (!open_segments_[index]->HaveOffset(id))
return false;
open_segments_[index]->AddUser();
open_entries_.insert(id);
return true;
}
// Segment is not open.
scoped_ptr<Segment> segment(new Segment(index, true, storage_));
if (!segment->Init() || !segment->HaveOffset(id))
return false;
segment->AddUser();
open_segments_[index] = segment.release();
open_entries_.insert(id);
return true;
}
bool LogStructuredStore::ReadData(int32 id, void* buffer, int32 size,
int32 offset) const {
DCHECK(init_ && !closed_);
DCHECK(open_entries_.find(id) != open_entries_.end());
int32 index = id / disk_cache::kFlashSegmentSize;
DCHECK(open_segments_[index] && open_segments_[index]->HaveOffset(id));
return open_segments_[index]->ReadData(buffer, size, id + offset);
}
void LogStructuredStore::CloseEntry(int32 id) {
DCHECK(init_ && !closed_);
std::set<int32>::iterator entry_iter = open_entries_.find(id);
DCHECK(entry_iter != open_entries_.end());
if (current_entry_id_ != -1) {
DCHECK(id == current_entry_id_ && !current_entry_num_bytes_left_to_write_);
open_entries_.erase(entry_iter);
current_entry_id_ = -1;
return;
}
int32 index = id / disk_cache::kFlashSegmentSize;
DCHECK(open_segments_[index]);
open_entries_.erase(entry_iter);
open_segments_[index]->ReleaseUser();
if (open_segments_[index]->HasNoUsers()) {
delete open_segments_[index];
open_segments_[index] = NULL;
}
}
int32 LogStructuredStore::GetNextSegmentIndex() {
DCHECK(init_ && !closed_);
int32 next_index = (write_index_ + 1) % num_segments_;
while (InUse(next_index)) {
next_index = (next_index + 1) % num_segments_;
DCHECK_NE(next_index, write_index_);
}
return next_index;
}
bool LogStructuredStore::InUse(int32 index) const {
DCHECK(init_ && !closed_);
DCHECK(index >= 0 && index < num_segments_);
return open_segments_[index] != NULL;
}
} // namespace disk_cache
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