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      1 // Copyright 2017 The Chromium OS Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef _BSDIFF_DIFF_ENCODER_H_
      6 #define _BSDIFF_DIFF_ENCODER_H_
      7 
      8 #include <stdint.h>
      9 
     10 #include "bsdiff/bz2_compressor.h"
     11 #include "bsdiff/patch_writer_interface.h"
     12 
     13 namespace bsdiff {
     14 
     15 // Helper class to encapsulate the diff and extra stream generation logic
     16 // derived from the old and new file buffers. Using this class is impossible to
     17 // produce an invalid or incomplete bsdiff patch, since it has checks in place
     18 // verifying its correct usage.
     19 
     20 class DiffEncoder {
     21  public:
     22   // Initialize the DiffEncoder with the old and new file buffers, as well as
     23   // the path writer used. The |patch| will be initialized when calling Init().
     24   DiffEncoder(PatchWriterInterface* patch,
     25               const uint8_t* old_buf,
     26               uint64_t old_size,
     27               const uint8_t* new_buf,
     28               uint64_t new_size)
     29       : patch_(patch),
     30         old_buf_(old_buf),
     31         old_size_(old_size),
     32         new_buf_(new_buf),
     33         new_size_(new_size) {}
     34 
     35   // Initialize the diff encoder and the underlying patch.
     36   bool Init();
     37 
     38   // Add a new control triplet entry to the patch. The |entry.diff_size| bytes
     39   // for the diff stream and the |entry.extra_size| bytes for the extra stream
     40   // will be computed and added to the corresponding streams in the patch.
     41   // Returns whether the operation succeeded. The operation can fail if either
     42   // the old or new files are referenced out of bounds.
     43   bool AddControlEntry(const ControlEntry& entry);
     44 
     45   // Finalize the patch writing process and close the underlying patch writer.
     46   bool Close();
     47 
     48  private:
     49   // Pointer to the patch we are writing to.
     50   PatchWriterInterface* patch_;
     51 
     52   // Old and new file buffers.
     53   const uint8_t* old_buf_;
     54   uint64_t old_size_;
     55   const uint8_t* new_buf_;
     56   uint64_t new_size_;
     57 
     58   // Bytes of the new_buf_ already written.
     59   uint64_t written_output_{0};
     60 
     61   // The current position in the old buf.
     62   int64_t old_pos_{0};
     63 };
     64 
     65 }  // namespace bsdiff
     66 
     67 #endif  // _BSDIFF_DIFF_ENCODER_H_
     68