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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 "net/disk_cache/mapped_file.h"
#include <stdlib.h>
#include "base/file_path.h"
#include "base/logging.h"
namespace disk_cache {
void* MappedFile::Init(const FilePath& name, size_t size) {
DCHECK(!init_);
if (init_ || !File::Init(name))
return NULL;
if (!size)
size = GetLength();
buffer_ = malloc(size);
snapshot_ = malloc(size);
if (buffer_ && snapshot_ && Read(buffer_, size, 0)) {
memcpy(snapshot_, buffer_, size);
} else {
free(buffer_);
free(snapshot_);
buffer_ = snapshot_ = 0;
}
init_ = true;
view_size_ = size;
return buffer_;
}
bool MappedFile::Load(const FileBlock* block) {
size_t offset = block->offset() + view_size_;
return Read(block->buffer(), block->size(), offset);
}
bool MappedFile::Store(const FileBlock* block) {
size_t offset = block->offset() + view_size_;
return Write(block->buffer(), block->size(), offset);
}
void MappedFile::Flush() {
DCHECK(buffer_);
DCHECK(snapshot_);
if (0 == memcmp(buffer_, snapshot_, view_size_)) {
// Nothing changed, no need to flush.
return;
}
const char* buffer_ptr = static_cast<const char*>(buffer_);
char* snapshot_ptr = static_cast<char*>(snapshot_);
size_t i = 0;
while (i < view_size_) {
size_t run_start = i;
// Look for a run of changed bytes (possibly zero-sized). Write them out.
while(i < view_size_ && snapshot_ptr[i] != buffer_ptr[i]) {
snapshot_ptr[i] = buffer_ptr[i];
i++;
}
if (i > run_start) {
Write(snapshot_ptr + run_start, i - run_start, run_start);
}
// Look for a run of unchanged bytes (possibly zero-sized). Skip them.
while (i < view_size_ && snapshot_ptr[i] == buffer_ptr[i]) {
i++;
}
}
DCHECK(0 == memcmp(buffer_, snapshot_, view_size_));
}
MappedFile::~MappedFile() {
if (!init_)
return;
if (buffer_ && snapshot_) {
Flush();
}
free(buffer_);
free(snapshot_);
}
} // namespace disk_cache
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