ceph/src/rocksdb/table/block_fetcher.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5 //
   6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   7 // Use of this source code is governed by a BSD-style license that can be
   8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   9
  10 #pragma once
  11 #include "table/block.h"
  12 #include "table/format.h"
  13 #include "util/memory_allocator.h"
  14
  15 namespace rocksdb {
  16 class BlockFetcher {
  17  public:
  18   // Read the block identified by "handle" from "file".
  19   // The only relevant option is options.verify_checksums for now.
  20   // On failure return non-OK.
  21   // On success fill *result and return OK - caller owns *result
  22   // @param uncompression_dict Data for presetting the compression library's
  23   //    dictionary.
  24   BlockFetcher(RandomAccessFileReader* file,
  25                FilePrefetchBuffer* prefetch_buffer, const Footer& footer,
  26                const ReadOptions& read_options, const BlockHandle& handle,
  27                BlockContents* contents, const ImmutableCFOptions& ioptions,
  28                bool do_uncompress, bool maybe_compressed,
  29                const UncompressionDict& uncompression_dict,
  30                const PersistentCacheOptions& cache_options,
  31                MemoryAllocator* memory_allocator = nullptr,
  32                MemoryAllocator* memory_allocator_compressed = nullptr)
  33       : file_(file),
  34         prefetch_buffer_(prefetch_buffer),
  35         footer_(footer),
  36         read_options_(read_options),
  37         handle_(handle),
  38         contents_(contents),
  39         ioptions_(ioptions),
  40         do_uncompress_(do_uncompress),
  41         maybe_compressed_(maybe_compressed),
  42         uncompression_dict_(uncompression_dict),
  43         cache_options_(cache_options),
  44         memory_allocator_(memory_allocator),
  45         memory_allocator_compressed_(memory_allocator_compressed) {}
  46   Status ReadBlockContents();
  47   CompressionType get_compression_type() const { return compression_type_; }
  48
  49  private:
  50   static const uint32_t kDefaultStackBufferSize = 5000;
  51
  52   RandomAccessFileReader* file_;
  53   FilePrefetchBuffer* prefetch_buffer_;
  54   const Footer& footer_;
  55   const ReadOptions read_options_;
  56   const BlockHandle& handle_;
  57   BlockContents* contents_;
  58   const ImmutableCFOptions& ioptions_;
  59   bool do_uncompress_;
  60   bool maybe_compressed_;
  61   const UncompressionDict& uncompression_dict_;
  62   const PersistentCacheOptions& cache_options_;
  63   MemoryAllocator* memory_allocator_;
  64   MemoryAllocator* memory_allocator_compressed_;
  65   Status status_;
  66   Slice slice_;
  67   char* used_buf_ = nullptr;
  68   size_t block_size_;
  69   CacheAllocationPtr heap_buf_;
  70   CacheAllocationPtr compressed_buf_;
  71   char stack_buf_[kDefaultStackBufferSize];
  72   bool got_from_prefetch_buffer_ = false;
  73   rocksdb::CompressionType compression_type_;
  74
  75   // return true if found
  76   bool TryGetUncompressBlockFromPersistentCache();
  77   // return true if found
  78   bool TryGetFromPrefetchBuffer();
  79   bool TryGetCompressedBlockFromPersistentCache();
  80   void PrepareBufferForBlockFromFile();
  81   // Copy content from used_buf_ to new heap buffer.
  82   void CopyBufferToHeap();
  83   void GetBlockContents();
  84   void InsertCompressedBlockToPersistentCacheIfNeeded();
  85   void InsertUncompressedBlockToPersistentCacheIfNeeded();
  86   void CheckBlockChecksum();
  87 };
  88 }  // namespace rocksdb