您最多选择25个主题
主题必须以字母或数字开头，可以包含连字符 (-)，并且长度不得超过35个字符
99 行
3.0 KiB
99 行
3.0 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#ifndef STORAGE_LEVELDB_TABLE_FORMAT_H_
|
|
#define STORAGE_LEVELDB_TABLE_FORMAT_H_
|
|
|
|
#include <cstdint>
|
|
#include <string>
|
|
|
|
#include "leveldb/slice.h"
|
|
#include "leveldb/status.h"
|
|
#include "leveldb/table_builder.h"
|
|
|
|
namespace leveldb {
|
|
|
|
class Block;
|
|
class RandomAccessFile;
|
|
struct ReadOptions;
|
|
|
|
// BlockHandle is a pointer to the extent of a file that stores a data
|
|
// block or a meta block.
|
|
class BlockHandle {
|
|
public:
|
|
// Maximum encoding length of a BlockHandle
|
|
enum { kMaxEncodedLength = 10 + 10 };
|
|
|
|
BlockHandle();
|
|
|
|
// The offset of the block in the file.
|
|
uint64_t offset() const { return offset_; }
|
|
void set_offset(uint64_t offset) { offset_ = offset; }
|
|
|
|
// The size of the stored block
|
|
uint64_t size() const { return size_; }
|
|
void set_size(uint64_t size) { size_ = size; }
|
|
|
|
void EncodeTo(std::string* dst) const;
|
|
Status DecodeFrom(Slice* input);
|
|
|
|
private:
|
|
uint64_t offset_;
|
|
uint64_t size_;
|
|
};
|
|
|
|
// Footer encapsulates the fixed information stored at the tail
|
|
// end of every table file.
|
|
class Footer {
|
|
public:
|
|
// Encoded length of a Footer. Note that the serialization of a
|
|
// Footer will always occupy exactly this many bytes. It consists
|
|
// of two block handles and a magic number.
|
|
enum { kEncodedLength = 2 * BlockHandle::kMaxEncodedLength + 8 };
|
|
|
|
Footer() = default;
|
|
|
|
// The block handle for the metaindex block of the table
|
|
const BlockHandle& metaindex_handle() const { return metaindex_handle_; }
|
|
void set_metaindex_handle(const BlockHandle& h) { metaindex_handle_ = h; }
|
|
|
|
// The block handle for the index block of the table
|
|
const BlockHandle& index_handle() const { return index_handle_; }
|
|
void set_index_handle(const BlockHandle& h) { index_handle_ = h; }
|
|
|
|
void EncodeTo(std::string* dst) const;
|
|
Status DecodeFrom(Slice* input);
|
|
|
|
private:
|
|
BlockHandle metaindex_handle_;
|
|
BlockHandle index_handle_;
|
|
};
|
|
|
|
// kTableMagicNumber was picked by running
|
|
// echo http://code.google.com/p/leveldb/ | sha1sum
|
|
// and taking the leading 64 bits.
|
|
static const uint64_t kTableMagicNumber = 0xdb4775248b80fb57ull;
|
|
|
|
// 1-byte type + 32-bit crc
|
|
static const size_t kBlockTrailerSize = 5;
|
|
|
|
struct BlockContents {
|
|
Slice data; // Actual contents of data
|
|
bool cachable; // True iff data can be cached
|
|
bool heap_allocated; // True iff caller should delete[] data.data()
|
|
};
|
|
|
|
// Read the block identified by "handle" from "file". On failure
|
|
// return non-OK. On success fill *result and return OK.
|
|
Status ReadBlock(RandomAccessFile* file, const ReadOptions& options,
|
|
const BlockHandle& handle, BlockContents* result);
|
|
|
|
// Implementation details follow. Clients should ignore,
|
|
|
|
inline BlockHandle::BlockHandle()
|
|
: offset_(~static_cast<uint64_t>(0)), size_(~static_cast<uint64_t>(0)) {}
|
|
|
|
} // namespace leveldb
|
|
|
|
#endif // STORAGE_LEVELDB_TABLE_FORMAT_H_
|