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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "vm/Compression.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/MemoryChecking.h"
#include "mozilla/PodOperations.h"
#include "mozilla/ScopeExit.h"
#include "js/Utility.h"
#include "util/Memory.h"
using namespace js;
static void* zlib_alloc(void* cx, uInt items, uInt size) {
return js_calloc(items, size);
}
static void zlib_free(void* cx, void* addr) { js_free(addr); }
Compressor::Compressor(const unsigned char* inp, size_t inplen)
: inp(inp),
inplen(inplen),
initialized(false),
finished(false),
currentChunkSize(0) {
MOZ_ASSERT(inplen > 0, "data to compress can't be empty");
zs.opaque = nullptr;
zs.next_in = (Bytef*)inp;
zs.avail_in = 0;
zs.next_out = nullptr;
zs.avail_out = 0;
zs.zalloc = zlib_alloc;
zs.zfree = zlib_free;
zs.total_in = 0;
zs.total_out = 0;
zs.msg = nullptr;
zs.state = nullptr;
zs.data_type = 0;
zs.adler = 0;
zs.reserved = 0;
// Reserve space for the CompressedDataHeader.
outbytes = sizeof(CompressedDataHeader);
}
Compressor::~Compressor() {
if (initialized) {
int ret = deflateEnd(&zs);
if (ret != Z_OK) {
// If we finished early, we can get a Z_DATA_ERROR.
MOZ_ASSERT(ret == Z_DATA_ERROR);
MOZ_ASSERT(!finished);
}
}
}
// According to the zlib docs, the default value for windowBits is 15. Passing
// -15 is treated the same, but it also forces 'raw deflate' (no zlib header or
// trailer). Raw deflate is necessary for chunked decompression.
static const int WindowBits = -15;
bool Compressor::init() {
if (inplen >= UINT32_MAX) {
return false;
}
// zlib is slow and we'd rather be done compression sooner
// even if it means decompression is slower which penalizes
// Function.toString()
int ret = deflateInit2(&zs, Z_BEST_SPEED, Z_DEFLATED, WindowBits, 8,
Z_DEFAULT_STRATEGY);
if (ret != Z_OK) {
MOZ_ASSERT(ret == Z_MEM_ERROR);
return false;
}
initialized = true;
return true;
}
void Compressor::setOutput(unsigned char* out, size_t outlen) {
MOZ_ASSERT(outlen > outbytes);
zs.next_out = out + outbytes;
zs.avail_out = outlen - outbytes;
}
Compressor::Status Compressor::compressMore() {
MOZ_ASSERT(zs.next_out);
uInt left = inplen - (zs.next_in - inp);
if (left <= MAX_INPUT_SIZE) {
zs.avail_in = left;
} else if (zs.avail_in == 0) {
zs.avail_in = MAX_INPUT_SIZE;
}
// Finish the current chunk if needed.
bool flush = false;
MOZ_ASSERT(currentChunkSize <= CHUNK_SIZE);
if (currentChunkSize + zs.avail_in >= CHUNK_SIZE) {
// Adjust avail_in, so we don't get chunks that are larger than
// CHUNK_SIZE.
zs.avail_in = CHUNK_SIZE - currentChunkSize;
MOZ_ASSERT(currentChunkSize + zs.avail_in == CHUNK_SIZE);
flush = true;
}
MOZ_ASSERT(zs.avail_in <= left);
bool done = zs.avail_in == left;
Bytef* oldin = zs.next_in;
Bytef* oldout = zs.next_out;
int ret = deflate(&zs, done ? Z_FINISH : (flush ? Z_FULL_FLUSH : Z_NO_FLUSH));
outbytes += zs.next_out - oldout;
currentChunkSize += zs.next_in - oldin;
MOZ_ASSERT(currentChunkSize <= CHUNK_SIZE);
if (ret == Z_MEM_ERROR) {
zs.avail_out = 0;
return OOM;
}
if (ret == Z_BUF_ERROR || (ret == Z_OK && zs.avail_out == 0)) {
// We have to resize the output buffer. Note that we're not done yet
// because ret != Z_STREAM_END.
MOZ_ASSERT(zs.avail_out == 0);
return MOREOUTPUT;
}
if (done || currentChunkSize == CHUNK_SIZE) {
MOZ_ASSERT_IF(!done, flush);
MOZ_ASSERT(chunkSize(inplen, chunkOffsets.length()) == currentChunkSize);
if (!chunkOffsets.append(outbytes)) {
return OOM;
}
currentChunkSize = 0;
MOZ_ASSERT_IF(done, chunkOffsets.length() == (inplen - 1) / CHUNK_SIZE + 1);
}
MOZ_ASSERT_IF(!done, ret == Z_OK);
MOZ_ASSERT_IF(done, ret == Z_STREAM_END);
return done ? DONE : CONTINUE;
}
size_t Compressor::totalBytesNeeded() const {
return AlignBytes(outbytes, sizeof(uint32_t)) + sizeOfChunkOffsets();
}
void Compressor::finish(char* dest, size_t destBytes) {
MOZ_ASSERT(!chunkOffsets.empty());
CompressedDataHeader* compressedHeader =
reinterpret_cast<CompressedDataHeader*>(dest);
compressedHeader->compressedBytes = outbytes;
size_t outbytesAligned = AlignBytes(outbytes, sizeof(uint32_t));
// Zero the padding bytes, the ImmutableStringsCache will hash them.
mozilla::PodZero(dest + outbytes, outbytesAligned - outbytes);
uint32_t* destArr = reinterpret_cast<uint32_t*>(dest + outbytesAligned);
MOZ_ASSERT(uintptr_t(dest + destBytes) ==
uintptr_t(destArr + chunkOffsets.length()));
mozilla::PodCopy(destArr, chunkOffsets.begin(), chunkOffsets.length());
finished = true;
}
bool js::DecompressString(const unsigned char* inp, size_t inplen,
unsigned char* out, size_t outlen) {
MOZ_ASSERT(inplen <= UINT32_MAX);
// Mark the memory we pass to zlib as initialized for MSan.
MOZ_MAKE_MEM_DEFINED(out, outlen);
z_stream zs;
zs.zalloc = zlib_alloc;
zs.zfree = zlib_free;
zs.opaque = nullptr;
zs.next_in = (Bytef*)inp;
zs.avail_in = inplen;
zs.next_out = out;
MOZ_ASSERT(outlen);
zs.avail_out = outlen;
int ret = inflateInit(&zs);
if (ret != Z_OK) {
MOZ_ASSERT(ret == Z_MEM_ERROR);
return false;
}
ret = inflate(&zs, Z_FINISH);
MOZ_ASSERT(ret == Z_STREAM_END);
ret = inflateEnd(&zs);
MOZ_ASSERT(ret == Z_OK);
return true;
}
bool js::DecompressStringChunk(const unsigned char* inp, size_t chunk,
unsigned char* out, size_t outlen) {
MOZ_ASSERT(outlen <= Compressor::CHUNK_SIZE);
const CompressedDataHeader* header =
reinterpret_cast<const CompressedDataHeader*>(inp);
size_t compressedBytes = header->compressedBytes;
size_t compressedBytesAligned = AlignBytes(compressedBytes, sizeof(uint32_t));
const unsigned char* offsetBytes = inp + compressedBytesAligned;
const uint32_t* offsets = reinterpret_cast<const uint32_t*>(offsetBytes);
uint32_t compressedStart =
chunk > 0 ? offsets[chunk - 1] : sizeof(CompressedDataHeader);
uint32_t compressedEnd = offsets[chunk];
MOZ_ASSERT(compressedStart < compressedEnd);
MOZ_ASSERT(compressedEnd <= compressedBytes);
bool lastChunk = compressedEnd == compressedBytes;
// Mark the memory we pass to zlib as initialized for MSan.
MOZ_MAKE_MEM_DEFINED(out, outlen);
z_stream zs;
zs.zalloc = zlib_alloc;
zs.zfree = zlib_free;
zs.opaque = nullptr;
zs.next_in = (Bytef*)(inp + compressedStart);
zs.avail_in = compressedEnd - compressedStart;
zs.next_out = out;
MOZ_ASSERT(outlen);
zs.avail_out = outlen;
// when release-asserts below are tripped.
volatile int ret = inflateInit2(&zs, WindowBits);
if (ret != Z_OK) {
MOZ_ASSERT(ret == Z_MEM_ERROR);
return false;
}
auto autoCleanup = mozilla::MakeScopeExit([&] {
mozilla::DebugOnly<int> ret = inflateEnd(&zs);
MOZ_ASSERT(ret == Z_OK);
});
if (lastChunk) {
ret = inflate(&zs, Z_FINISH);
MOZ_RELEASE_ASSERT(ret == Z_STREAM_END);
} else {
ret = inflate(&zs, Z_NO_FLUSH);
if (ret == Z_MEM_ERROR) {
return false;
}
MOZ_RELEASE_ASSERT(ret == Z_OK);
}
MOZ_ASSERT(zs.avail_in == 0);
MOZ_ASSERT(zs.avail_out == 0);
return true;
}