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_ENDSLEY_PATCH_WRITER_H_ 6 #define _BSDIFF_ENDSLEY_PATCH_WRITER_H_ 7 8 #include <memory> 9 #include <string> 10 #include <vector> 11 12 #include "bsdiff/compressor_interface.h" 13 #include "bsdiff/constants.h" 14 #include "bsdiff/patch_writer_interface.h" 15 16 namespace bsdiff { 17 18 // A PatchWriterInterface class compatible with the format used by Android Play 19 // Store's bsdiff implementation, which is based on Matthew Endsley's bsdiff 20 // implementation. See https://github.com/mendsley/bsdiff for the original 21 // implementation of this format. See also Google's APK patch size estimator for 22 // more information on the file-by-file format used by Play Store: 23 // https://github.com/googlesamples/apk-patch-size-estimator 24 25 // This format, identified by the "ENDSLEY/BSDIFF43" magic string, uses a single 26 // stream with the control entries, diff data and extra data interleaved. After 27 // the header, each Control Entry is stored in 24 bytes followed by the diff 28 // stream data for that entry only, and then followed by the extra stream data 29 // for that entry only. The format doesn't handle the compression of the data, 30 // instead, the whole file (including the magic string) is compressed with any 31 // compression algorithm. 32 33 // This format is easier to parse and allows the patch to be streamed, but by 34 // mixing the diff and extra data into the same compression context offers a 35 // slightly worse compression ratio (about 3.5% compared to upstream's format). 36 37 class EndsleyPatchWriter : public PatchWriterInterface { 38 public: 39 // Create the patch writer that will write the data to the passed vector 40 // |patch|, resizing it as needed. The |patch| vector must be valid until 41 // Close() is called or this patch is destroyed. The data in |patch| will be 42 // compressed using the compressor type |type|. 43 EndsleyPatchWriter(std::vector<uint8_t>* patch, 44 CompressorType type, 45 int brotli_quality) 46 : patch_(patch), 47 compressor_type_(type), 48 brotli_quality_(brotli_quality) {} 49 50 // PatchWriterInterface overrides. 51 bool Init(size_t new_size) override; 52 bool WriteDiffStream(const uint8_t* data, size_t size) override; 53 bool WriteExtraStream(const uint8_t* data, size_t size) override; 54 bool AddControlEntry(const ControlEntry& entry) override; 55 bool Close() override; 56 57 private: 58 // Emit at the end of the |patch_| vector the passed control entry. 59 void EmitControlEntry(const ControlEntry& entry); 60 61 // Emit at the end of the |patch_| vector the passed buffer. 62 void EmitBuffer(const uint8_t* data, size_t size); 63 64 // Flush as much as possible of the pending data. 65 void Flush(); 66 67 // The vector we are writing to, owned by the caller. 68 std::vector<uint8_t>* patch_; 69 70 // The compressor type to use and its quality (if any). 71 CompressorType compressor_type_; 72 int brotli_quality_; 73 74 std::unique_ptr<CompressorInterface> compressor_; 75 76 // The pending diff and extra data to be encoded in the file. These vectors 77 // would not be used whenever is possible to the data directly to the patch_ 78 // vector; namely when the control, diff and extra stream data are provided in 79 // that order for each control entry. 80 std::vector<uint8_t> diff_data_; 81 std::vector<uint8_t> extra_data_; 82 std::vector<ControlEntry> control_; 83 84 // Defined as the sum of all the diff_size and extra_size values in 85 // |control_|. This is used to determine whether it is worth Flushing the 86 // pending data. 87 size_t pending_control_data_{0}; 88 89 // Number of bytes in the diff and extra stream that are pending in the 90 // last control entry encoded in the |patch_|. If both are zero the last 91 // control entry was completely emitted. 92 size_t pending_diff_{0}; 93 size_t pending_extra_{0}; 94 }; 95 96 } // namespace bsdiff 97 98 #endif // _BSDIFF_ENDSLEY_PATCH_WRITER_H_ 99
