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https://github.com/scratchfoundation/scratch-html5.git
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81 lines
2.5 KiB
JavaScript
81 lines
2.5 KiB
JavaScript
// Copyright (C) 2013 Massachusetts Institute of Technology
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License version 2,
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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// Provides the equivalent functionality of an AS ByteArray
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// using JavaScript ArrayBuffers and viewers
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var OffsetBuffer = function(data) {
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this.offset = 0;
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this.ab = data;
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};
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// Read various datatypes from the ArrayBuffer, seeking the offset.
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OffsetBuffer.prototype.readString = function(length) {
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var str = this.ab2str(this.ab.slice(this.offset, this.offset + length));
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this.offset += length;
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return str;
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};
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OffsetBuffer.prototype.readInt = function() {
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var num = this.ab2int(this.ab.slice(this.offset, this.offset + 4));
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this.offset += 4;
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return num;
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};
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OffsetBuffer.prototype.readUint = function() {
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var num = this.ab2uint(this.ab.slice(this.offset, this.offset + 4));
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this.offset += 4;
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return num;
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};
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OffsetBuffer.prototype.readShort = function() {
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var num = this.ab2short(this.ab.slice(this.offset, this.offset + 2));
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this.offset += 2;
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return num;
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};
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OffsetBuffer.prototype.readBytes = function(length) {
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var bytes = this.ab.slice(this.offset, this.offset + length);
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this.offset += length;
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return bytes;
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};
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// Length of the internal buffer
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OffsetBuffer.prototype.getLength = function() {
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return this.ab.byteLength;
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};
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// Number of bytes remaining from the current offset
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OffsetBuffer.prototype.bytesAvailable = function() {
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return this.getLength() - this.offset;
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};
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// ArrayBuffer -> JS type conversion methods
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OffsetBuffer.prototype.ab2str = function(buf) {
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return String.fromCharCode.apply(null, new Uint8Array(buf));
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};
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// These create Javascript Numbers
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OffsetBuffer.prototype.ab2int = function(buf) {
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return new Int32Array(buf)[0];
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};
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OffsetBuffer.prototype.ab2uint = function(buf) {
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return new Uint32Array(buf)[0];
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};
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OffsetBuffer.prototype.ab2short = function(buf) {
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return new Int16Array(buf)[0];
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};
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