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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root 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 "table/block.h"
#include "table/format.h"
#include "util/memory_allocator.h"
namespace rocksdb {
class BlockFetcher {
public:
// Read the block identified by "handle" from "file".
// The only relevant option is options.verify_checksums for now.
// On failure return non-OK.
// On success fill *result and return OK - caller owns *result
// @param uncompression_dict Data for presetting the compression library's
// dictionary.
BlockFetcher(RandomAccessFileReader* file,
FilePrefetchBuffer* prefetch_buffer, const Footer& footer,
const ReadOptions& read_options, const BlockHandle& handle,
BlockContents* contents, const ImmutableCFOptions& ioptions,
bool do_uncompress, bool maybe_compressed,
const UncompressionDict& uncompression_dict,
const PersistentCacheOptions& cache_options,
MemoryAllocator* memory_allocator = nullptr,
MemoryAllocator* memory_allocator_compressed = nullptr)
: file_(file),
prefetch_buffer_(prefetch_buffer),
footer_(footer),
read_options_(read_options),
handle_(handle),
contents_(contents),
ioptions_(ioptions),
do_uncompress_(do_uncompress),
maybe_compressed_(maybe_compressed),
uncompression_dict_(uncompression_dict),
cache_options_(cache_options),
memory_allocator_(memory_allocator),
memory_allocator_compressed_(memory_allocator_compressed) {}
Status ReadBlockContents();
CompressionType get_compression_type() const { return compression_type_; }
private:
static const uint32_t kDefaultStackBufferSize = 5000;
RandomAccessFileReader* file_;
FilePrefetchBuffer* prefetch_buffer_;
const Footer& footer_;
const ReadOptions read_options_;
const BlockHandle& handle_;
BlockContents* contents_;
const ImmutableCFOptions& ioptions_;
bool do_uncompress_;
bool maybe_compressed_;
const UncompressionDict& uncompression_dict_;
const PersistentCacheOptions& cache_options_;
MemoryAllocator* memory_allocator_;
MemoryAllocator* memory_allocator_compressed_;
Status status_;
Slice slice_;
char* used_buf_ = nullptr;
size_t block_size_;
CacheAllocationPtr heap_buf_;
CacheAllocationPtr compressed_buf_;
char stack_buf_[kDefaultStackBufferSize];
bool got_from_prefetch_buffer_ = false;
rocksdb::CompressionType compression_type_;
// return true if found
bool TryGetUncompressBlockFromPersistentCache();
// return true if found
bool TryGetFromPrefetchBuffer();
bool TryGetCompressedBlockFromPersistentCache();
void PrepareBufferForBlockFromFile();
// Copy content from used_buf_ to new heap buffer.
void CopyBufferToHeap();
void GetBlockContents();
void InsertCompressedBlockToPersistentCacheIfNeeded();
void InsertUncompressedBlockToPersistentCacheIfNeeded();
void CheckBlockChecksum();
};
} // namespace rocksdb
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