mirror of https://github.com/facebook/rocksdb.git
126 lines
4.1 KiB
C++
126 lines
4.1 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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// Log format information shared by reader and writer.
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#pragma once
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#ifndef ROCKSDB_LITE
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#include <limits>
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#include <memory>
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#include <utility>
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#include "rocksdb/options.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/status.h"
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#include "rocksdb/types.h"
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namespace rocksdb {
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namespace blob_db {
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constexpr uint32_t kMagicNumber = 2395959; // 0x00248f37
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constexpr uint32_t kVersion1 = 1;
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constexpr uint64_t kNoExpiration = std::numeric_limits<uint64_t>::max();
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using ExpirationRange = std::pair<uint64_t, uint64_t>;
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// Format of blob log file header (30 bytes):
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//
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// +--------------+---------+---------+-------+-------------+-------------------+
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// | magic number | version | cf id | flags | compression | expiration range |
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// +--------------+---------+---------+-------+-------------+-------------------+
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// | Fixed32 | Fixed32 | Fixed32 | char | char | Fixed64 Fixed64 |
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// +--------------+---------+---------+-------+-------------+-------------------+
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//
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// List of flags:
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// has_ttl: Whether the file contain TTL data.
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//
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// Expiration range in the header is a rough range based on
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// blob_db_options.ttl_range_secs.
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struct BlobLogHeader {
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static constexpr size_t kSize = 30;
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uint32_t version = kVersion1;
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uint32_t column_family_id = 0;
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CompressionType compression = kNoCompression;
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bool has_ttl = false;
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ExpirationRange expiration_range = std::make_pair(0, 0);
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void EncodeTo(std::string* dst);
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Status DecodeFrom(Slice slice);
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};
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// Format of blob log file footer (32 bytes):
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//
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// +--------------+------------+-------------------+------------+
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// | magic number | blob count | expiration range | footer CRC |
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// +--------------+------------+-------------------+------------+
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// | Fixed32 | Fixed64 | Fixed64 + Fixed64 | Fixed32 |
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// +--------------+------------+-------------------+------------+
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//
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// The footer will be presented only when the blob file is properly closed.
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//
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// Unlike the same field in file header, expiration range in the footer is the
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// range of smallest and largest expiration of the data in this file.
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struct BlobLogFooter {
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static constexpr size_t kSize = 32;
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uint64_t blob_count = 0;
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ExpirationRange expiration_range = std::make_pair(0, 0);
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uint32_t crc = 0;
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void EncodeTo(std::string* dst);
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Status DecodeFrom(Slice slice);
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};
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// Blob record format (32 bytes header + key + value):
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//
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// +------------+--------------+------------+------------+----------+---------+-----------+
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// | key length | value length | expiration | header CRC | blob CRC | key | value |
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// +------------+--------------+------------+------------+----------+---------+-----------+
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// | Fixed64 | Fixed64 | Fixed64 | Fixed32 | Fixed32 | key len | value len |
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// +------------+--------------+------------+------------+----------+---------+-----------+
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//
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// If file has has_ttl = false, expiration field is always 0, and the blob
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// doesn't has expiration.
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//
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// Also note that if compression is used, value is compressed value and value
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// length is compressed value length.
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//
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// Header CRC is the checksum of (key_len + val_len + expiration), while
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// blob CRC is the checksum of (key + value).
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//
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// We could use variable length encoding (Varint64) to save more space, but it
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// make reader more complicated.
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struct BlobLogRecord {
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// header include fields up to blob CRC
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static constexpr size_t kHeaderSize = 32;
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uint64_t key_size = 0;
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uint64_t value_size = 0;
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uint64_t expiration = 0;
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uint32_t header_crc = 0;
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uint32_t blob_crc = 0;
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Slice key;
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Slice value;
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std::unique_ptr<char[]> key_buf;
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std::unique_ptr<char[]> value_buf;
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uint64_t record_size() const { return kHeaderSize + key_size + value_size; }
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void EncodeHeaderTo(std::string* dst);
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Status DecodeHeaderFrom(Slice src);
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Status CheckBlobCRC() const;
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};
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} // namespace blob_db
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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