1    :  // Copyright 2012 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #ifndef SYZYGY_BLOCK_GRAPH_BLOCK_HASH_H_
  16    :  #define SYZYGY_BLOCK_GRAPH_BLOCK_HASH_H_
  17    :  
  18    :  #include "base/md5.h"
  19    :  #include "syzygy/block_graph/block_graph.h"
  20    :  #include "syzygy/common/comparable.h"
  21    :  
  22    :  namespace block_graph {
  23    :  
  24    :  using block_graph::BlockGraph;
  25    :  
  26    :  // Represents a hash of the content of a block. Internally we store an 128-bit
  27    :  // MD5 digest, but this endows it with comparison operators. We explicitly
  28    :  // provide copy and assignment operators to make this STL container compatible.
  29    :  struct BlockHash : public common::Comparable<BlockHash> {
  30    :   public:
  31    :    BlockHash() {
  32    :    }
  33    :  
  34    :    // Constructor from Block.
  35  E :    explicit BlockHash(const BlockGraph::Block* block) {
  36  E :      Hash(block);
  37  E :    }
  38    :  
  39    :    // General comparison function, required by Comparable.
  40  E :    int Compare(const BlockHash& other) const {
  41  E :      return memcmp(&md5_digest, &other.md5_digest, sizeof(md5_digest));
  42  E :    }
  43    :  
  44    :    // Populates this block hash from the given block. The hash is calculated
  45    :    // on the block content and its references, as follows:
  46    :    //     Block properties: type, size, data_size, reference count
  47    :    //     References (increasing source offset): source offset, type, size
  48    :    //     Data (skipping references)
  49    :    void Hash(const BlockGraph::Block* block);
  50    :  
  51    :    base::MD5Digest md5_digest;
  52    :  };
  53    :  
  54    :  }  // namespace block_graph
  55    :  
  56    :  #endif  // SYZYGY_BLOCK_GRAPH_BLOCK_HASH_H_