The Tor Browser: toolkit/components/workerlz4/lz4.js@925c144e1f1f (annotated)

toolkit/components/workerlz4/lz4.js@925c144e1f1f (annotated)

toolkit/components/workerlz4/lz4.js

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 /* 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 || null);
   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;