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