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author | dgrogan@chromium.org <dgrogan@chromium.org@62dab493-f737-651d-591e-8d6aee1b9529> | 2011-04-19 23:11:15 +0000 |
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committer | dgrogan@chromium.org <dgrogan@chromium.org@62dab493-f737-651d-591e-8d6aee1b9529> | 2011-04-19 23:11:15 +0000 |
commit | 69c6d38342a1fab5f7f2921aa2e9c0e60ba90e35 (patch) | |
tree | bea96813c653d9e32277cb86cb517ddd90d0595c /table/format.h | |
parent | b743906eeabc925f3e824d91a9747012bf249e2f (diff) | |
download | leveldb-69c6d38342a1fab5f7f2921aa2e9c0e60ba90e35.tar.gz |
reverting disastrous MOE commit, returning to r21
git-svn-id: https://leveldb.googlecode.com/svn/trunk@23 62dab493-f737-651d-591e-8d6aee1b9529
Diffstat (limited to 'table/format.h')
-rw-r--r-- | table/format.h | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/table/format.h b/table/format.h new file mode 100644 index 0000000..a6ab964 --- /dev/null +++ b/table/format.h @@ -0,0 +1,103 @@ +// 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; + +// Read the block identified by "handle" from "file". On success, +// store a pointer to the heap-allocated result in *block and return +// OK. On failure store NULL in *block and return non-OK. +extern Status ReadBlock(RandomAccessFile* file, + const ReadOptions& options, + const BlockHandle& handle, + Block** block); + +// Implementation details follow. Clients should ignore, + +inline BlockHandle::BlockHandle() + : offset_(~static_cast<uint64_t>(0)), + size_(~static_cast<uint64_t>(0)) { +} + +} + +#endif // STORAGE_LEVELDB_TABLE_FORMAT_H_ |