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// Copyright 2020 the V8 project 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 "src/snapshot/snapshot-compression.h"
#include "src/utils/memcopy.h"
#include "third_party/zlib/google/compression_utils_portable.h"
namespace v8 {
namespace internal {
uint32_t GetUncompressedSize(const Bytef* compressed_data) {
uint32_t size;
MemCopy(&size, compressed_data, sizeof(size));
return size;
}
SnapshotData SnapshotCompression::Compress(
const SnapshotData* uncompressed_data) {
SnapshotData snapshot_data;
base::ElapsedTimer timer;
if (FLAG_profile_deserialization) timer.Start();
static_assert(sizeof(Bytef) == 1, "");
const uLongf input_size =
static_cast<uLongf>(uncompressed_data->RawData().size());
uint32_t payload_length =
static_cast<uint32_t>(uncompressed_data->RawData().size());
uLongf compressed_data_size = compressBound(input_size);
// Allocating >= the final amount we will need.
snapshot_data.AllocateData(
static_cast<uint32_t>(sizeof(payload_length) + compressed_data_size));
byte* compressed_data = const_cast<byte*>(snapshot_data.RawData().begin());
// Since we are doing raw compression (no zlib or gzip headers), we need to
// manually store the uncompressed size.
MemCopy(compressed_data, &payload_length, sizeof(payload_length));
CHECK_EQ(zlib_internal::CompressHelper(
zlib_internal::ZRAW, compressed_data + sizeof(payload_length),
&compressed_data_size,
bit_cast<const Bytef*>(uncompressed_data->RawData().begin()),
input_size, Z_DEFAULT_COMPRESSION, nullptr, nullptr),
Z_OK);
// Reallocating to exactly the size we need.
snapshot_data.Resize(static_cast<uint32_t>(compressed_data_size) +
sizeof(payload_length));
DCHECK_EQ(payload_length,
GetUncompressedSize(snapshot_data.RawData().begin()));
if (FLAG_profile_deserialization) {
double ms = timer.Elapsed().InMillisecondsF();
PrintF("[Compressing %d bytes took %0.3f ms]\n", payload_length, ms);
}
return snapshot_data;
}
SnapshotData SnapshotCompression::Decompress(
Vector<const byte> compressed_data) {
SnapshotData snapshot_data;
base::ElapsedTimer timer;
if (FLAG_profile_deserialization) timer.Start();
const Bytef* input_bytef = bit_cast<const Bytef*>(compressed_data.begin());
// Since we are doing raw compression (no zlib or gzip headers), we need to
// manually retrieve the uncompressed size.
uint32_t uncompressed_payload_length = GetUncompressedSize(input_bytef);
input_bytef += sizeof(uncompressed_payload_length);
snapshot_data.AllocateData(uncompressed_payload_length);
uLongf uncompressed_size = uncompressed_payload_length;
CHECK_EQ(zlib_internal::UncompressHelper(
zlib_internal::ZRAW,
bit_cast<Bytef*>(snapshot_data.RawData().begin()),
&uncompressed_size, input_bytef,
static_cast<uLong>(compressed_data.size() -
sizeof(uncompressed_payload_length))),
Z_OK);
if (FLAG_profile_deserialization) {
double ms = timer.Elapsed().InMillisecondsF();
PrintF("[Decompressing %d bytes took %0.3f ms]\n",
uncompressed_payload_length, ms);
}
return snapshot_data;
}
} // namespace internal
} // namespace v8
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