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rocksdb/table/block.h

191 lines
5.7 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.
//
// 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.
#pragma once
#include <stddef.h>
#include <stdint.h>
#include "rocksdb/iterator.h"
#include "rocksdb/options.h"
#include "db/dbformat.h"
namespace rocksdb {
struct BlockContents;
class Comparator;
class BlockIter;
class BlockHashIndex;
class BlockPrefixIndex;
class Block {
public:
// Initialize the block with the specified contents.
explicit Block(const BlockContents& contents);
~Block();
size_t size() const { return size_; }
const char* data() const { return data_; }
bool cachable() const { return cachable_; }
uint32_t NumRestarts() const;
CompressionType compression_type() const { return compression_type_; }
// If hash index lookup is enabled and `use_hash_index` is true. This block
// will do hash lookup for the key prefix.
//
// NOTE: for the hash based lookup, if a key prefix doesn't match any key,
// the iterator will simply be set as "invalid", rather than returning
// the key that is just pass the target key.
//
// If iter is null, return new Iterator
// If iter is not null, update this one and return it as Iterator*
Iterator* NewIterator(const Comparator* comparator,
BlockIter* iter = nullptr);
void SetBlockHashIndex(BlockHashIndex* hash_index);
void SetBlockPrefixIndex(BlockPrefixIndex* prefix_index);
// Report an approximation of how much memory has been used.
size_t ApproximateMemoryUsage() const;
private:
const char* data_;
size_t size_;
uint32_t restart_offset_; // Offset in data_ of restart array
bool owned_; // Block owns data_[]
bool cachable_;
CompressionType compression_type_;
std::unique_ptr<BlockHashIndex> hash_index_;
std::unique_ptr<BlockPrefixIndex> prefix_index_;
// No copying allowed
Block(const Block&);
void operator=(const Block&);
};
class BlockIter : public Iterator {
public:
BlockIter()
: comparator_(nullptr),
data_(nullptr),
restarts_(0),
num_restarts_(0),
current_(0),
restart_index_(0),
status_(Status::OK()),
hash_index_(nullptr),
prefix_index_(nullptr) {}
BlockIter(const Comparator* comparator, const char* data, uint32_t restarts,
uint32_t num_restarts, BlockHashIndex* hash_index,
BlockPrefixIndex* prefix_index)
: BlockIter() {
Initialize(comparator, data, restarts, num_restarts,
hash_index, prefix_index);
}
void Initialize(const Comparator* comparator, const char* data,
uint32_t restarts, uint32_t num_restarts, BlockHashIndex* hash_index,
BlockPrefixIndex* prefix_index) {
assert(data_ == nullptr); // Ensure it is called only once
assert(num_restarts > 0); // Ensure the param is valid
comparator_ = comparator;
data_ = data;
restarts_ = restarts;
num_restarts_ = num_restarts;
current_ = restarts_;
restart_index_ = num_restarts_;
hash_index_ = hash_index;
prefix_index_ = prefix_index;
}
void SetStatus(Status s) {
status_ = s;
}
virtual bool Valid() const override { return current_ < restarts_; }
virtual Status status() const override { return status_; }
virtual Slice key() const override {
assert(Valid());
return key_.GetKey();
}
virtual Slice value() const override {
assert(Valid());
return value_;
}
virtual void Next() override;
virtual void Prev() override;
virtual void Seek(const Slice& target) override;
virtual void SeekToFirst() override;
virtual void SeekToLast() override;
private:
const Comparator* comparator_;
const char* data_; // underlying block contents
uint32_t restarts_; // Offset of restart array (list of fixed32)
uint32_t num_restarts_; // Number of uint32_t entries in restart array
// current_ is offset in data_ of current entry. >= restarts_ if !Valid
uint32_t current_;
uint32_t restart_index_; // Index of restart block in which current_ falls
IterKey key_;
Slice value_;
Status status_;
BlockHashIndex* hash_index_;
BlockPrefixIndex* prefix_index_;
inline int Compare(const Slice& a, const Slice& b) const {
return comparator_->Compare(a, b);
}
// Return the offset in data_ just past the end of the current entry.
inline uint32_t NextEntryOffset() const {
return (value_.data() + value_.size()) - data_;
}
uint32_t GetRestartPoint(uint32_t index) {
assert(index < num_restarts_);
return DecodeFixed32(data_ + restarts_ + index * sizeof(uint32_t));
}
void SeekToRestartPoint(uint32_t index) {
key_.Clear();
restart_index_ = index;
// current_ will be fixed by ParseNextKey();
// ParseNextKey() starts at the end of value_, so set value_ accordingly
uint32_t offset = GetRestartPoint(index);
value_ = Slice(data_ + offset, 0);
}
void CorruptionError();
bool ParseNextKey();
bool BinarySeek(const Slice& target, uint32_t left, uint32_t right,
uint32_t* index);
int CompareBlockKey(uint32_t block_index, const Slice& target);
bool BinaryBlockIndexSeek(const Slice& target, uint32_t* block_ids,
uint32_t left, uint32_t right,
uint32_t* index);
bool HashSeek(const Slice& target, uint32_t* index);
bool PrefixSeek(const Slice& target, uint32_t* index);
};
} // namespace rocksdb