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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "xz_utils.h"
#include <vector>
#include "base/array_ref.h"
#include "dwarf/writer.h"
#include "base/leb128.h"
// liblzma.
#include "7zCrc.h"
#include "XzCrc64.h"
#include "XzEnc.h"
namespace art {
namespace debug {
constexpr size_t kChunkSize = kPageSize;
static void XzCompressChunk(ArrayRef<uint8_t> src, std::vector<uint8_t>* dst) {
// Configure the compression library.
CrcGenerateTable();
Crc64GenerateTable();
CLzma2EncProps lzma2Props;
Lzma2EncProps_Init(&lzma2Props);
lzma2Props.lzmaProps.level = 1; // Fast compression.
Lzma2EncProps_Normalize(&lzma2Props);
CXzProps props;
XzProps_Init(&props);
props.lzma2Props = lzma2Props;
// Implement the required interface for communication (written in C so no virtual methods).
struct XzCallbacks : public ISeqInStream, public ISeqOutStream, public ICompressProgress {
static SRes ReadImpl(const ISeqInStream* p, void* buf, size_t* size) {
auto* ctx = static_cast<XzCallbacks*>(const_cast<ISeqInStream*>(p));
*size = std::min(*size, ctx->src_.size() - ctx->src_pos_);
memcpy(buf, ctx->src_.data() + ctx->src_pos_, *size);
ctx->src_pos_ += *size;
return SZ_OK;
}
static size_t WriteImpl(const ISeqOutStream* p, const void* buf, size_t size) {
auto* ctx = static_cast<const XzCallbacks*>(p);
const uint8_t* buffer = reinterpret_cast<const uint8_t*>(buf);
ctx->dst_->insert(ctx->dst_->end(), buffer, buffer + size);
return size;
}
static SRes ProgressImpl(const ICompressProgress* , UInt64, UInt64) {
return SZ_OK;
}
size_t src_pos_;
ArrayRef<uint8_t> src_;
std::vector<uint8_t>* dst_;
};
XzCallbacks callbacks;
callbacks.Read = XzCallbacks::ReadImpl;
callbacks.Write = XzCallbacks::WriteImpl;
callbacks.Progress = XzCallbacks::ProgressImpl;
callbacks.src_pos_ = 0;
callbacks.src_ = src;
callbacks.dst_ = dst;
// Compress.
SRes res = Xz_Encode(&callbacks, &callbacks, &props, &callbacks);
CHECK_EQ(res, SZ_OK);
}
// Compress data while splitting it to smaller chunks to enable random-access reads.
// The XZ file format supports this well, but the compression library does not.
// Therefore compress the chunks separately and then glue them together manually.
//
// The XZ file format is described here: https://tukaani.org/xz/xz-file-format.txt
// In short, the file format is: [header] [compressed_block]* [index] [footer]
// Where [index] is: [num_records] ([compressed_size] [uncompressed_size])* [crc32]
//
void XzCompress(ArrayRef<uint8_t> src, std::vector<uint8_t>* dst) {
uint8_t header[] = { 0xFD, '7', 'z', 'X', 'Z', 0, 0, 1, 0x69, 0x22, 0xDE, 0x36 };
uint8_t footer[] = { 0, 1, 'Y', 'Z' };
dst->insert(dst->end(), header, header + sizeof(header));
std::vector<uint8_t> tmp;
std::vector<uint32_t> index;
for (size_t offset = 0; offset < src.size(); offset += kChunkSize) {
size_t size = std::min(src.size() - offset, kChunkSize);
tmp.clear();
XzCompressChunk(src.SubArray(offset, size), &tmp);
DCHECK_EQ(memcmp(tmp.data(), header, sizeof(header)), 0);
DCHECK_EQ(memcmp(tmp.data() + tmp.size() - sizeof(footer), footer, sizeof(footer)), 0);
uint32_t* index_size = reinterpret_cast<uint32_t*>(tmp.data() + tmp.size() - 8);
DCHECK_ALIGNED(index_size, sizeof(uint32_t));
size_t index_offset = tmp.size() - 16 - *index_size * 4;
const uint8_t* index_ptr = tmp.data() + index_offset;
uint8_t index_indicator = *(index_ptr++);
CHECK_EQ(index_indicator, 0); // Mark the start of index (as opposed to compressed block).
uint32_t num_records = DecodeUnsignedLeb128(&index_ptr);
for (uint32_t i = 0; i < num_records; i++) {
index.push_back(DecodeUnsignedLeb128(&index_ptr)); // Compressed size.
index.push_back(DecodeUnsignedLeb128(&index_ptr)); // Uncompressed size.
}
// Copy the raw compressed block(s) located between the header and index.
dst->insert(dst->end(), tmp.data() + sizeof(header), tmp.data() + index_offset);
}
// Write the index.
uint32_t index_size_in_words;
{
tmp.clear();
dwarf::Writer<> writer(&tmp);
writer.PushUint8(0); // Index indicator.
writer.PushUleb128(static_cast<uint32_t>(index.size()) / 2); // Record count.
for (uint32_t i : index) {
writer.PushUleb128(i);
}
writer.Pad(4);
index_size_in_words = writer.size() / sizeof(uint32_t);
writer.PushUint32(CrcCalc(tmp.data(), tmp.size()));
dst->insert(dst->end(), tmp.begin(), tmp.end());
}
// Write the footer.
{
tmp.clear();
dwarf::Writer<> writer(&tmp);
writer.PushUint32(0); // CRC placeholder.
writer.PushUint32(index_size_in_words);
writer.PushData(footer, sizeof(footer));
writer.UpdateUint32(0, CrcCalc(tmp.data() + 4, 6));
dst->insert(dst->end(), tmp.begin(), tmp.end());
}
}
} // namespace debug
} // namespace art
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