blob: 3fe3d8d6a9438d820ea3ba06bc9463f7c99f1565 [file] [log] [blame]
// Copyright 2021 The Fuchsia 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 "compression.h"
#include <inttypes.h>
#include <log.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <lz4/lz4frame.h>
static LZ4F_dctx* lz4_context = NULL;
static const void* compressed_input = NULL;
static size_t compressed_size = 0;
// LZ4 decompression doesn't always want the entire input at once, each time we
// process a chunk it will give us the optimal input size for the next call.
static size_t next_input_size = 0;
// Returns true if we're in the middle of decompression.
static bool decompress_running(void) { return compressed_input != NULL; }
bool decompress_start(const void* input, size_t size) {
DLOG("Starting decompression of %zu bytes", size);
if (decompress_running()) {
ELOG("a decompression is already in progress");
return false;
if (!input || size == 0) {
ELOG("no data to decompress");
return false;
LZ4F_errorCode_t result = LZ4F_createDecompressionContext(&lz4_context, LZ4F_VERSION);
if (LZ4F_isError(result)) {
ELOG("failed to create LZ4 decompression context: %s", LZ4F_getErrorName(result));
return false;
compressed_input = input;
compressed_size = next_input_size = size;
return true;
void decompress_stop(void) {
if (lz4_context) {
LZ4F_errorCode_t result = LZ4F_freeDecompressionContext(lz4_context);
if (LZ4F_isError(result)) {
WLOG("decompression did not fully complete: %s", LZ4F_getErrorName(result));
lz4_context = NULL;
compressed_input = NULL;
compressed_size = next_input_size = 0;
decompress_result_t decompress_next_chunk(void** output, size_t* size) {
// 4MiB is the maximum LZ4 block size, always reserve this much space for
// simplicity. If this becomes an issue we could check the frame for this
// particular frame's max block size and dynamically allocate instead.
static uint8_t decompress_buffer[4 * 1024 * 1024];
if (!decompress_running()) {
ELOG("no decompression currently running");
DLOG("Decompressing up to the next %zu bytes", next_input_size);
size_t source_bytes = next_input_size;
size_t dest_bytes = sizeof(decompress_buffer);
size_t result = LZ4F_decompress(lz4_context, decompress_buffer, &dest_bytes, compressed_input,
&source_bytes, NULL);
if (LZ4F_isError(result)) {
ELOG("decompression failure (%s)", LZ4F_getErrorName(result));
DLOG("Decompressed %zu -> %zu bytes", source_bytes, dest_bytes);
next_input_size = result;
compressed_input += source_bytes;
*output = decompress_buffer;
*size = dest_bytes;