Refactor bsdiff patch writing code to another file.

bsdiff.cc had code to handle both the sub-streams compression and the
patch format. This CL moves the patch file format logic to a new class
in a separated file, and the bzip2 compression to another class. This
allows to replace the core bsdiff logic separatedly from the patch
format.

There are no changes to the functionality of bsdiff and the generated
patches. The code does a bit more of memcpy() since it doesn't write
the control stream to disk as it goes.

Bug: 34220646
Test: Ran bsdiff and compared results with previous version.

Change-Id: Ibdc1482e98cbd370cbed677c326008e19a217ef8

1 files changed, 116 insertions, 0 deletions

diff --git a/bz2_compressor.cc b/bz2_compressor.cc
new file mode 100644
index 0000000..69b27e5
--- /dev/null
+++ b/bz2_compressor.cc
@@ -0,0 +1,116 @@
+// Copyright 2017 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "bz2_compressor.h"
+
+#include <string.h>
+
+#include "logging.h"
+
+using std::endl;
+
+namespace {
+
+// The BZ2 compression level used. Smaller compression levels are nowadays
+// pointless.
+const int kCompressionLevel = 9;
+
+}  // namespace
+
+namespace bsdiff {
+
+BZ2Compressor::BZ2Compressor() {
+  memset(&bz_strm_, 0, sizeof(bz_strm_));
+  int bz_err = BZ2_bzCompressInit(&bz_strm_, kCompressionLevel,
+                                  0 /* verbosity */, 0 /* workFactor */);
+  if (bz_err != BZ_OK) {
+    LOG(ERROR) << "Initializing bz_strm, bz_error=" << bz_err << endl;
+  } else {
+    bz_strm_initialized_ = true;
+  }
+  comp_buffer_.resize(1024 * 1024);
+}
+
+BZ2Compressor::~BZ2Compressor() {
+  if (!bz_strm_initialized_)
+    return;
+  int bz_err = BZ2_bzCompressEnd(&bz_strm_);
+  if (bz_err != BZ_OK) {
+    LOG(ERROR) << "Deleting the compressor stream, bz_error=" << bz_err << endl;
+  }
+}
+
+bool BZ2Compressor::Write(const uint8_t* buf, size_t size) {
+  if (!bz_strm_initialized_)
+    return false;
+
+  // The bz_stream struct defines the next_in as a non-const data pointer,
+  // although the documentation says it won't modify it.
+  bz_strm_.next_in = reinterpret_cast<char*>(const_cast<uint8_t*>(buf));
+  bz_strm_.avail_in = size;
+
+  while (bz_strm_.avail_in) {
+    bz_strm_.next_out = reinterpret_cast<char*>(comp_buffer_.data());
+    bz_strm_.avail_out = comp_buffer_.size();
+    int bz_err = BZ2_bzCompress(&bz_strm_, BZ_RUN);
+    if (bz_err != BZ_RUN_OK) {
+      LOG(ERROR) << "Compressing data, bz_error=" << bz_err << endl;
+      return false;
+    }
+
+    uint64_t output_bytes = comp_buffer_.size() - bz_strm_.avail_out;
+    if (output_bytes) {
+      comp_chunks_.emplace_back(comp_buffer_.data(),
+                                comp_buffer_.data() + output_bytes);
+    }
+  }
+  return true;
+}
+
+bool BZ2Compressor::Finish() {
+  if (!bz_strm_initialized_)
+    return false;
+  bz_strm_.next_in = nullptr;
+  bz_strm_.avail_in = 0;
+
+  int bz_err = BZ_FINISH_OK;
+  while (bz_err == BZ_FINISH_OK) {
+    bz_strm_.next_out = reinterpret_cast<char*>(comp_buffer_.data());
+    bz_strm_.avail_out = comp_buffer_.size();
+    bz_err = BZ2_bzCompress(&bz_strm_, BZ_FINISH);
+
+    uint64_t output_bytes = comp_buffer_.size() - bz_strm_.avail_out;
+    if (output_bytes) {
+      comp_chunks_.emplace_back(comp_buffer_.data(),
+                                comp_buffer_.data() + output_bytes);
+    }
+  }
+  if (bz_err != BZ_STREAM_END) {
+    LOG(ERROR) << "Finishing compressing data, bz_error=" << bz_err << endl;
+    return false;
+  }
+  bz_err = BZ2_bzCompressEnd(&bz_strm_);
+  bz_strm_initialized_ = false;
+  if (bz_err != BZ_OK) {
+    LOG(ERROR) << "Deleting the compressor stream, bz_error=" << bz_err << endl;
+    return false;
+  }
+  return true;
+}
+
+const std::vector<uint8_t>& BZ2Compressor::GetCompressedData() {
+  if (!comp_chunks_.empty()) {
+    size_t chunks_size = 0;
+    for (const auto& chunk : comp_chunks_)
+      chunks_size += chunk.size();
+    comp_data_.reserve(comp_data_.size() + chunks_size);
+    for (const auto& chunk : comp_chunks_) {
+      comp_data_.insert(comp_data_.end(), chunk.begin(), chunk.end());
+    }
+    comp_chunks_.clear();
+  }
+  return comp_data_;
+}
+
+}  // namespace bsdiff