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// Copyright 2011 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Asynchronous hash computer for the Blob interface.
*
* The Blob interface, part of the HTML5 File API, is supported on Chrome 7+,
* Firefox 4.0 and Opera 11. No Blob interface implementation is expected on
* Internet Explorer 10. Chrome 11, Firefox 5.0 and the subsequent release of
* Opera are supposed to use vendor prefixes due to evolving API, see
* http://dev.w3.org/2006/webapi/FileAPI/ for details.
*
* This implementation currently uses upcoming Chrome and Firefox prefixes,
* plus the original Blob.slice specification, as implemented on Chrome 10
* and Firefox 4.0.
*
*/
goog.provide('goog.crypt.BlobHasher');
goog.provide('goog.crypt.BlobHasher.EventType');
goog.require('goog.asserts');
goog.require('goog.crypt');
goog.require('goog.crypt.Hash');
goog.require('goog.debug.Logger');
goog.require('goog.events.EventTarget');
goog.require('goog.fs');
/**
* Construct the hash computer.
*
* @param {!goog.crypt.Hash} hashFn The hash function to use.
* @param {number=} opt_blockSize Processing block size.
* @constructor
* @extends {goog.events.EventTarget}
*/
goog.crypt.BlobHasher = function(hashFn, opt_blockSize) {
goog.base(this);
/**
* The actual hash function.
* @type {!goog.crypt.Hash}
* @private
*/
this.hashFn_ = hashFn;
/**
* The blob being processed.
* @type {Blob}
* @private
*/
this.blob_ = null;
/**
* Computed hash value.
* @type {Array.<number>}
* @private
*/
this.hashVal_ = null;
/**
* Number of bytes already processed.
* @type {number}
* @private
*/
this.bytesProcessed_ = 0;
/**
* Processing block size.
* @type {number}
* @private
*/
this.blockSize_ = opt_blockSize || 5000000;
/**
* File reader object.
* @type {FileReader}
* @private
*/
this.fileReader_ = null;
/**
* The logger used by this object.
* @type {!goog.debug.Logger}
* @private
*/
this.logger_ = goog.debug.Logger.getLogger('goog.crypt.BlobHasher');
};
goog.inherits(goog.crypt.BlobHasher, goog.events.EventTarget);
/**
* Event names for hash computation events
* @enum {string}
*/
goog.crypt.BlobHasher.EventType = {
STARTED: 'started',
PROGRESS: 'progress',
COMPLETE: 'complete',
ABORT: 'abort',
ERROR: 'error'
};
/**
* Start the hash computation.
* @param {!Blob} blob The blob of data to compute the hash for.
*/
goog.crypt.BlobHasher.prototype.hash = function(blob) {
this.abort();
this.hashFn_.reset();
this.blob_ = blob;
this.hashVal_ = null;
this.bytesProcessed_ = 0;
this.dispatchEvent(goog.crypt.BlobHasher.EventType.STARTED);
this.processNextBlock_();
};
/**
* Abort hash computation.
*/
goog.crypt.BlobHasher.prototype.abort = function() {
if (this.fileReader_ &&
this.fileReader_.readyState != this.fileReader_.DONE) {
this.fileReader_.abort();
}
};
/**
* @return {number} Number of bytes processed so far.
*/
goog.crypt.BlobHasher.prototype.getBytesProcessed = function() {
return this.bytesProcessed_;
};
/**
* @return {Array.<number>} The computed hash value or null if not ready.
*/
goog.crypt.BlobHasher.prototype.getHash = function() {
return this.hashVal_;
};
/**
* Helper function setting up the processing for the next block, or finalizing
* the computation if all blocks were processed.
* @private
*/
goog.crypt.BlobHasher.prototype.processNextBlock_ = function() {
goog.asserts.assert(this.blob_, 'The blob has disappeared during processing');
if (this.bytesProcessed_ < this.blob_.size) {
// We have to reset the FileReader every time, otherwise it fails on
// Chrome, including the latest Chrome 12 beta.
// http://code.google.com/p/chromium/issues/detail?id=82346
this.fileReader_ = new FileReader();
this.fileReader_.onload = goog.bind(this.onLoad_, this);
this.fileReader_.onabort = goog.bind(this.dispatchEvent, this,
goog.crypt.BlobHasher.EventType.ABORT);
this.fileReader_.onerror = goog.bind(this.dispatchEvent, this,
goog.crypt.BlobHasher.EventType.ERROR);
var size = Math.min(this.blob_.size - this.bytesProcessed_,
this.blockSize_);
var chunk = goog.fs.sliceBlob(this.blob_, this.bytesProcessed_,
this.bytesProcessed_ + size);
if (!chunk || chunk.size != size) {
this.logger_.severe('Failed slicing the blob');
this.dispatchEvent(goog.crypt.BlobHasher.EventType.ERROR);
return;
}
if (this.fileReader_.readAsArrayBuffer) {
this.fileReader_.readAsArrayBuffer(chunk);
} else if (this.fileReader_.readAsBinaryString) {
this.fileReader_.readAsBinaryString(chunk);
} else {
this.logger_.severe('Failed calling the chunk reader');
this.dispatchEvent(goog.crypt.BlobHasher.EventType.ERROR);
}
} else {
this.hashVal_ = this.hashFn_.digest();
this.dispatchEvent(goog.crypt.BlobHasher.EventType.COMPLETE);
}
};
/**
* Handle processing block loaded.
* @private
*/
goog.crypt.BlobHasher.prototype.onLoad_ = function() {
this.logger_.info('Successfully loaded a chunk');
var array = null;
if (this.fileReader_.result instanceof Array ||
goog.isString(this.fileReader_.result)) {
array = this.fileReader_.result;
} else if (goog.global['ArrayBuffer'] && goog.global['Uint8Array'] &&
this.fileReader_.result instanceof ArrayBuffer) {
array = new Uint8Array(this.fileReader_.result);
}
if (!array) {
this.logger_.severe('Failed reading the chunk');
this.dispatchEvent(goog.crypt.BlobHasher.EventType.ERROR);
return;
}
this.hashFn_.update(array);
this.bytesProcessed_ += array.length;
this.dispatchEvent(goog.crypt.BlobHasher.EventType.PROGRESS);
this.processNextBlock_();
};
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