gecko/toolkit/components/workerlz4/lz4.js
2014-01-09 17:10:04 +01:00

137 lines
5.3 KiB
JavaScript

/* 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 file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
if (typeof Components != "undefined") {
throw new Error("This file is meant to be loaded in a worker");
}
if (!module || !exports) {
throw new Error("Please load this module with require()");
}
const SharedAll = require("resource://gre/modules/osfile/osfile_shared_allthreads.jsm");
const Internals = require("resource://gre/modules/workers/lz4_internal.js");
const MAGIC_NUMBER = new Uint8Array([109, 111, 122, 76, 122, 52, 48, 0]); // "mozLz4a\0"
const BYTES_IN_SIZE_HEADER = ctypes.uint32_t.size;
const HEADER_SIZE = MAGIC_NUMBER.byteLength + BYTES_IN_SIZE_HEADER;
const EXPECTED_HEADER_TYPE = new ctypes.ArrayType(ctypes.uint8_t, HEADER_SIZE);
const EXPECTED_SIZE_BUFFER_TYPE = new ctypes.ArrayType(ctypes.uint8_t, BYTES_IN_SIZE_HEADER);
/**
* An error during (de)compression
*
* @param {string} operation The name of the operation ("compress", "decompress")
* @param {string} reason A reason to be used when matching errors. Must start
* with "because", e.g. "becauseInvalidContent".
* @param {string} message A human-readable message.
*/
function LZError(operation, reason, message) {
SharedAll.OSError.call(this);
this.operation = operation;
this[reason] = true;
this.message = message;
}
LZError.prototype = Object.create(SharedAll.OSError);
LZError.prototype.toString = function toString() {
return this.message;
};
exports.Error = LZError;
/**
* Compress a block to a form suitable for writing to disk.
*
* Compatibility note: For the moment, we are basing our code on lz4
* 1.3, which does not specify a *file* format. Therefore, we define
* our own format. Once lz4 defines a complete file format, we will
* migrate both |compressFileContent| and |decompressFileContent| to this file
* format. For backwards-compatibility, |decompressFileContent| will however
* keep the ability to decompress files provided with older versions of
* |compressFileContent|.
*
* Compressed files have the following layout:
*
* | MAGIC_NUMBER (8 bytes) | content size (uint32_t, little endian) | content, as obtained from lz4_compress |
*
* @param {TypedArray|void*} buffer The buffer to write to the disk.
* @param {object=} options An object that may contain the following fields:
* - {number} bytes The number of bytes to read from |buffer|. If |buffer|
* is an |ArrayBuffer|, |bytes| defaults to |buffer.byteLength|. If
* |buffer| is a |void*|, |bytes| MUST be provided.
* @return {Uint8Array} An array of bytes suitable for being written to the
* disk.
*/
function compressFileContent(array, options = {}) {
// Prepare the output array
let inputBytes;
if (SharedAll.isTypedArray(array) && !(options && "bytes" in options)) {
inputBytes = array.byteLength;
} else if (options && options.bytes) {
inputBytes = options.bytes;
} else {
throw new TypeError("compressFileContent requires a size");
}
let maxCompressedSize = Internals.maxCompressedSize(inputBytes);
let outputArray = new Uint8Array(HEADER_SIZE + maxCompressedSize);
// Compress to output array
let payload = new Uint8Array(outputArray.buffer, outputArray.byteOffset + HEADER_SIZE);
let compressedSize = Internals.compress(array, inputBytes, payload);
// Add headers
outputArray.set(MAGIC_NUMBER);
let view = new DataView(outputArray.buffer);
view.setUint32(MAGIC_NUMBER.byteLength, inputBytes, true);
return new Uint8Array(outputArray.buffer, 0, HEADER_SIZE + compressedSize);
}
exports.compressFileContent = compressFileContent;
function decompressFileContent(array, options = {}) {
let {ptr, bytes} = SharedAll.normalizeToPointer(array, options.bytes);
if (bytes < HEADER_SIZE) {
throw new LZError("decompress", "becauseLZNoHeader", "Buffer is too short (no header)");
}
// Read headers
let expectMagicNumber = ctypes.cast(ptr, EXPECTED_HEADER_TYPE.ptr).contents;
for (let i = 0; i < MAGIC_NUMBER.byteLength; ++i) {
if (expectMagicNumber[i] != MAGIC_NUMBER[i]) {
throw new LZError("decompress", "becauseLZWrongMagicNumber", "Invalid header (no magic number");
}
}
let sizeBuf =
ctypes.cast(
SharedAll.offsetBy(ptr, MAGIC_NUMBER.byteLength),
EXPECTED_SIZE_BUFFER_TYPE.ptr).contents;
let expectDecompressedSize =
sizeBuf[0] + (sizeBuf[1] << 8) + (sizeBuf[2] << 16) + (sizeBuf[3] << 24);
if (expectDecompressedSize == 0) {
// The underlying algorithm cannot handle a size of 0
return new Uint8Array(0);
}
// Prepare the input buffer
let inputPtr = SharedAll.offsetBy(ptr, HEADER_SIZE);
// Prepare the output buffer
let outputBuffer = new Uint8Array(expectDecompressedSize);
let decompressedBytes = (new SharedAll.Type.size_t.implementation(0));
// Decompress
let success = Internals.decompress(inputPtr, bytes - HEADER_SIZE,
outputBuffer, outputBuffer.byteLength,
decompressedBytes.address());
if (!success) {
throw new LZError("decompress", "becauseLZInvalidContent", "Invalid content:Decompression stopped at " + decompressedBytes.value);
}
return new Uint8Array(outputBuffer.buffer, outputBuffer.byteOffset, decompressedBytes.value);
}
exports.decompressFileContent = decompressFileContent;