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// 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 "bsdiff/endsley_patch_writer.h"
#include <string.h>
#include <algorithm>
#include "bsdiff/brotli_compressor.h"
#include "bsdiff/bz2_compressor.h"
#include "bsdiff/logging.h"
namespace {
constexpr uint8_t kEndsleyMagicHeader[] = "ENDSLEY/BSDIFF43";
void EncodeInt64(int64_t x, uint8_t* buf) {
uint64_t y = x < 0 ? (1ULL << 63ULL) - x : x;
for (int i = 0; i < 8; ++i) {
buf[i] = y & 0xff;
y /= 256;
}
}
// The minimum size that we would consider flushing out.
constexpr size_t kMinimumFlushSize = 1024 * 1024; // 1 MiB
} // namespace
namespace bsdiff {
bool EndsleyPatchWriter::Init(size_t new_size) {
switch (compressor_type_) {
case CompressorType::kNoCompression:
// The patch is uncompressed and it will need exactly:
// new_size + 24 * len(control_entries) + sizeof(header)
// We don't know the length of the control entries yet, but we can reserve
// enough space to hold at least |new_size|.
patch_->clear();
patch_->reserve(new_size);
break;
case CompressorType::kBrotli:
compressor_.reset(new BrotliCompressor(brotli_quality_));
if (!compressor_) {
LOG(ERROR) << "Error creating brotli compressor.";
return false;
}
break;
case CompressorType::kBZ2:
compressor_.reset(new BZ2Compressor());
if (!compressor_) {
LOG(ERROR) << "Error creating BZ2 compressor.";
return false;
}
break;
}
// Header is the magic followed by the new length.
uint8_t header[24];
memcpy(header, kEndsleyMagicHeader, 16);
EncodeInt64(new_size, header + 16);
EmitBuffer(header, sizeof(header));
return true;
}
bool EndsleyPatchWriter::WriteDiffStream(const uint8_t* data, size_t size) {
if (!size)
return true;
// Speed-up the common case where the diff stream data is added right after
// the control entry that refers to it.
if (control_.empty() && pending_diff_ >= size) {
pending_diff_ -= size;
EmitBuffer(data, size);
return true;
}
diff_data_.insert(diff_data_.end(), data, data + size);
return true;
}
bool EndsleyPatchWriter::WriteExtraStream(const uint8_t* data, size_t size) {
if (!size)
return true;
// Speed-up the common case where the extra stream data is added right after
// the diff stream data and the control entry that refers to it. Note that
// the diff data comes first so we need to make sure it is all out.
if (control_.empty() && !pending_diff_ && pending_extra_ >= size) {
pending_extra_ -= size;
EmitBuffer(data, size);
return true;
}
extra_data_.insert(extra_data_.end(), data, data + size);
return true;
}
bool EndsleyPatchWriter::AddControlEntry(const ControlEntry& entry) {
// Speed-up the common case where the control entry is added when there's
// nothing else pending.
if (control_.empty() && diff_data_.empty() && extra_data_.empty() &&
!pending_diff_ && !pending_extra_) {
pending_diff_ = entry.diff_size;
pending_extra_ = entry.extra_size;
EmitControlEntry(entry);
return true;
}
control_.push_back(entry);
pending_control_data_ += entry.diff_size + entry.extra_size;
// Check whether it is worth Flushing the entries now that the we have more
// control entries. We need control entries to write enough output data, and
// we need that output data to be at least 50% of the available diff and extra
// data. This last requirement is to reduce the overhead of removing the
// flushed data.
if (pending_control_data_ > kMinimumFlushSize &&
(diff_data_.size() + extra_data_.size()) / 2 <= pending_control_data_) {
Flush();
}
return true;
}
bool EndsleyPatchWriter::Close() {
// Flush any pending data.
Flush();
if (pending_diff_ || pending_extra_ || !control_.empty()) {
LOG(ERROR) << "Insufficient data sent to diff/extra streams";
return false;
}
if (!diff_data_.empty() || !extra_data_.empty()) {
LOG(ERROR) << "Pending data to diff/extra not flushed out on Close()";
return false;
}
if (compressor_) {
if (!compressor_->Finish())
return false;
*patch_ = compressor_->GetCompressedData();
}
return true;
}
void EndsleyPatchWriter::EmitControlEntry(const ControlEntry& entry) {
// Generate the 24 byte control entry.
uint8_t buf[24];
EncodeInt64(entry.diff_size, buf);
EncodeInt64(entry.extra_size, buf + 8);
EncodeInt64(entry.offset_increment, buf + 16);
EmitBuffer(buf, sizeof(buf));
}
void EndsleyPatchWriter::EmitBuffer(const uint8_t* data, size_t size) {
if (compressor_) {
compressor_->Write(data, size);
} else {
patch_->insert(patch_->end(), data, data + size);
}
}
void EndsleyPatchWriter::Flush() {
size_t used_diff = 0;
size_t used_extra = 0;
size_t used_control = 0;
do {
if (!pending_diff_ && !pending_extra_ && used_control < control_.size()) {
// We can emit a control entry in these conditions.
const ControlEntry& entry = control_[used_control];
used_control++;
pending_diff_ = entry.diff_size;
pending_extra_ = entry.extra_size;
pending_control_data_ -= entry.extra_size + entry.diff_size;
EmitControlEntry(entry);
}
if (pending_diff_) {
size_t diff_size = std::min(diff_data_.size() - used_diff, pending_diff_);
EmitBuffer(diff_data_.data() + used_diff, diff_size);
pending_diff_ -= diff_size;
used_diff += diff_size;
}
if (!pending_diff_ && pending_extra_) {
size_t extra_size =
std::min(extra_data_.size() - used_extra, pending_extra_);
EmitBuffer(extra_data_.data() + used_extra, extra_size);
pending_extra_ -= extra_size;
used_extra += extra_size;
}
} while (!pending_diff_ && !pending_extra_ && used_control < control_.size());
if (used_diff)
diff_data_.erase(diff_data_.begin(), diff_data_.begin() + used_diff);
if (used_extra)
extra_data_.erase(extra_data_.begin(), extra_data_.begin() + used_extra);
if (used_control)
control_.erase(control_.begin(), control_.begin() + used_control);
}
} // namespace bsdiff
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