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rocksdb/table/plain_table_key_coding.h

149 lines
6.0 KiB

// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#pragma once
#ifndef ROCKSDB_LITE
#include "rocksdb/slice.h"
#include "db/dbformat.h"
namespace rocksdb {
class WritableFile;
struct ParsedInternalKey;
struct PlainTableReaderFileInfo;
enum PlainTableEntryType : unsigned char;
// Helper class to write out a key to an output file
// Actual data format of the key is documented in plain_table_factory.h
class PlainTableKeyEncoder {
public:
explicit PlainTableKeyEncoder(EncodingType encoding_type,
uint32_t user_key_len,
const SliceTransform* prefix_extractor,
size_t index_sparseness)
: encoding_type_((prefix_extractor != nullptr) ? encoding_type : kPlain),
fixed_user_key_len_(user_key_len),
prefix_extractor_(prefix_extractor),
index_sparseness_((index_sparseness > 1) ? index_sparseness : 1),
key_count_for_prefix_(0) {}
// key: the key to write out, in the format of internal key.
// file: the output file to write out
// offset: offset in the file. Needs to be updated after appending bytes
// for the key
// meta_bytes_buf: buffer for extra meta bytes
// meta_bytes_buf_size: offset to append extra meta bytes. Will be updated
// if meta_bytes_buf is updated.
Status AppendKey(const Slice& key, WritableFileWriter* file, uint64_t* offset,
char* meta_bytes_buf, size_t* meta_bytes_buf_size);
// Return actual encoding type to be picked
EncodingType GetEncodingType() { return encoding_type_; }
private:
EncodingType encoding_type_;
uint32_t fixed_user_key_len_;
const SliceTransform* prefix_extractor_;
const size_t index_sparseness_;
size_t key_count_for_prefix_;
IterKey pre_prefix_;
};
// A helper class to decode keys from input buffer
// Actual data format of the key is documented in plain_table_factory.h
class PlainTableKeyDecoder {
public:
explicit PlainTableKeyDecoder(const PlainTableReaderFileInfo* file_info,
EncodingType encoding_type,
uint32_t user_key_len,
const SliceTransform* prefix_extractor)
: file_reader_(file_info),
encoding_type_(encoding_type),
prefix_len_(0),
fixed_user_key_len_(user_key_len),
prefix_extractor_(prefix_extractor),
in_prefix_(false) {}
// Find the next key.
// start: char array where the key starts.
// limit: boundary of the char array
// parsed_key: the output of the result key
// internal_key: if not null, fill with the output of the result key in
// un-parsed format
// bytes_read: how many bytes read from start. Output
// seekable: whether key can be read from this place. Used when building
// indexes. Output.
Status NextKey(uint32_t start_offset, ParsedInternalKey* parsed_key,
Slice* internal_key, Slice* value, uint32_t* bytes_read,
bool* seekable = nullptr);
Status NextKeyNoValue(uint32_t start_offset, ParsedInternalKey* parsed_key,
Slice* internal_key, uint32_t* bytes_read,
bool* seekable = nullptr);
class FileReader {
public:
explicit FileReader(const PlainTableReaderFileInfo* file_info)
: file_info_(file_info),
buf_start_offset_(0),
buf_len_(0),
buf_capacity_(0) {}
// In mmaped mode, the results point to mmaped area of the file, which
// means it is always valid before closing the file.
// In non-mmap mode, the results point to an internal buffer. If the caller
// makes another read call, the results will not be valid. So callers should
// make a copy when needed.
// If return false, status code is stored in status_.
inline bool Read(uint32_t file_offset, uint32_t len, Slice* output);
// If return false, status code is stored in status_.
bool ReadNonMmap(uint32_t file_offset, uint32_t len, Slice* output);
// *bytes_read = 0 means eof. false means failure and status is saved
// in status_. Not directly returning Status to save copying status
// object to map previous performance of mmap mode.
inline bool ReadVarint32(uint32_t offset, uint32_t* output,
uint32_t* bytes_read);
bool ReadVarint32NonMmap(uint32_t offset, uint32_t* output,
uint32_t* bytes_read);
Status status() const { return status_; }
const PlainTableReaderFileInfo* file_info_;
std::unique_ptr<char[]> buf_;
uint32_t buf_start_offset_;
uint32_t buf_len_;
uint32_t buf_capacity_;
Status status_;
};
FileReader file_reader_;
EncodingType encoding_type_;
uint32_t prefix_len_;
uint32_t fixed_user_key_len_;
Slice saved_user_key_;
IterKey cur_key_;
const SliceTransform* prefix_extractor_;
bool in_prefix_;
private:
Status NextPlainEncodingKey(uint32_t start_offset,
ParsedInternalKey* parsed_key,
Slice* internal_key, uint32_t* bytes_read,
bool* seekable = nullptr);
Status NextPrefixEncodingKey(uint32_t start_offset,
ParsedInternalKey* parsed_key,
Slice* internal_key, uint32_t* bytes_read,
bool* seekable = nullptr);
Status ReadInternalKey(uint32_t file_offset, uint32_t user_key_size,
ParsedInternalKey* parsed_key, uint32_t* bytes_read,
bool* internal_key_valid, Slice* internal_key);
inline Status DecodeSize(uint32_t start_offset,
PlainTableEntryType* entry_type, uint32_t* key_size,
uint32_t* bytes_read);
};
} // namespace rocksdb
#endif // ROCKSDB_LITE