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https://github.com/facebook/rocksdb.git
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c073ed7601
Summary: Fix typo in comments and code. Pull Request resolved: https://github.com/facebook/rocksdb/pull/10233 Test Plan: Existing unit tests should pass. Reviewed By: jay-zhuang, anand1976 Differential Revision: D37356702 Pulled By: gitbw95 fbshipit-source-id: 32c019adcc6dcc95a9882b38147a310091368e51
129 lines
4.4 KiB
C++
129 lines
4.4 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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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include <cstdint>
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#include <memory>
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#include "db/log_format.h"
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#include "rocksdb/compression_type.h"
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#include "rocksdb/env.h"
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#include "rocksdb/io_status.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/status.h"
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#include "util/compression.h"
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namespace ROCKSDB_NAMESPACE {
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class WritableFileWriter;
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namespace log {
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/**
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* Writer is a general purpose log stream writer. It provides an append-only
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* abstraction for writing data. The details of the how the data is written is
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* handled by the WritableFile sub-class implementation.
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*
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* File format:
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*
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* File is broken down into variable sized records. The format of each record
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* is described below.
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* +-----+-------------+--+----+----------+------+-- ... ----+
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* File | r0 | r1 |P | r2 | r3 | r4 | |
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* +-----+-------------+--+----+----------+------+-- ... ----+
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* <--- kBlockSize ------>|<-- kBlockSize ------>|
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* rn = variable size records
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* P = Padding
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*
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* Data is written out in kBlockSize chunks. If next record does not fit
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* into the space left, the leftover space will be padded with \0.
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*
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* Legacy record format:
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*
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* +---------+-----------+-----------+--- ... ---+
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* |CRC (4B) | Size (2B) | Type (1B) | Payload |
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* +---------+-----------+-----------+--- ... ---+
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*
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* CRC = 32bit hash computed over the record type and payload using CRC
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* Size = Length of the payload data
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* Type = Type of record
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* (kZeroType, kFullType, kFirstType, kLastType, kMiddleType )
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* The type is used to group a bunch of records together to represent
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* blocks that are larger than kBlockSize
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* Payload = Byte stream as long as specified by the payload size
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*
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* Recyclable record format:
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*
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* +---------+-----------+-----------+----------------+--- ... ---+
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* |CRC (4B) | Size (2B) | Type (1B) | Log number (4B)| Payload |
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* +---------+-----------+-----------+----------------+--- ... ---+
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*
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* Same as above, with the addition of
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* Log number = 32bit log file number, so that we can distinguish between
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* records written by the most recent log writer vs a previous one.
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*/
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class Writer {
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public:
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// Create a writer that will append data to "*dest".
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// "*dest" must be initially empty.
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// "*dest" must remain live while this Writer is in use.
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explicit Writer(std::unique_ptr<WritableFileWriter>&& dest,
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uint64_t log_number, bool recycle_log_files,
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bool manual_flush = false,
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CompressionType compressionType = kNoCompression);
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// No copying allowed
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Writer(const Writer&) = delete;
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void operator=(const Writer&) = delete;
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~Writer();
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IOStatus AddRecord(const Slice& slice,
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Env::IOPriority rate_limiter_priority = Env::IO_TOTAL);
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IOStatus AddCompressionTypeRecord();
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WritableFileWriter* file() { return dest_.get(); }
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const WritableFileWriter* file() const { return dest_.get(); }
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uint64_t get_log_number() const { return log_number_; }
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IOStatus WriteBuffer();
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IOStatus Close();
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bool TEST_BufferIsEmpty();
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private:
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std::unique_ptr<WritableFileWriter> dest_;
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size_t block_offset_; // Current offset in block
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uint64_t log_number_;
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bool recycle_log_files_;
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// crc32c values for all supported record types. These are
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// pre-computed to reduce the overhead of computing the crc of the
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// record type stored in the header.
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uint32_t type_crc_[kMaxRecordType + 1];
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IOStatus EmitPhysicalRecord(
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RecordType type, const char* ptr, size_t length,
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Env::IOPriority rate_limiter_priority = Env::IO_TOTAL);
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// If true, it does not flush after each write. Instead it relies on the upper
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// layer to manually does the flush by calling ::WriteBuffer()
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bool manual_flush_;
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// Compression Type
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CompressionType compression_type_;
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StreamingCompress* compress_;
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// Reusable compressed output buffer
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std::unique_ptr<char[]> compressed_buffer_;
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};
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} // namespace log
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} // namespace ROCKSDB_NAMESPACE
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