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+// 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 <string>
+#include <stdint.h>
+#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:
+ 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);
+
+ // Maximum encoding length of a BlockHandle
+ enum { kMaxEncodedLength = 10 + 10 };
+
+ private:
+ uint64_t offset_;
+ uint64_t size_;
+};
+
+// Footer encapsulates the fixed information stored at the tail
+// end of every table file.
+class Footer {
+ public:
+ Footer() { }
+
+ // 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);
+
+ // 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
+ };
+
+ 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.
+extern 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_