126 lines
3.5 KiB
JavaScript
126 lines
3.5 KiB
JavaScript
// BinaryReader
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// Refactored by Vjeux <vjeuxx@gmail.com>
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// http://blog.vjeux.com/2010/javascript/javascript-binary-reader.html
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// Original
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//+ Jonas Raoni Soares Silva
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//@ http://jsfromhell.com/classes/binary-parser [rev. #1]
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BinaryReader = function (data) {
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this._buffer = data;
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this._pos = 0;
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};
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BinaryReader.prototype = {
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/* Public */
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readInt8: function (){ return this._decodeInt(8, true); },
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readUInt8: function (){ return this._decodeInt(8, false); },
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readInt16: function (){ return this._decodeInt(16, true); },
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readUInt16: function (){ return this._decodeInt(16, false); },
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readInt32: function (){ return this._decodeInt(32, true); },
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readUInt32: function (){ return this._decodeInt(32, false); },
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readFloat: function (){ return this._decodeFloat(23, 8); },
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readDouble: function (){ return this._decodeFloat(52, 11); },
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readChar: function () { return this.readString(1); },
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readString: function (length) {
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this._checkSize(length * 8);
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var result = this._buffer.substr(this._pos, length);
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this._pos += length;
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return result;
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},
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seek: function (pos) {
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this._pos = pos;
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this._checkSize(0);
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},
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getPosition: function () {
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return this._pos;
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},
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getSize: function () {
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return this._buffer.length;
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},
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/* Private */
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_decodeFloat: function(precisionBits, exponentBits){
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var length = precisionBits + exponentBits + 1;
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var size = length >> 3;
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this._checkSize(length);
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var bias = Math.pow(2, exponentBits - 1) - 1;
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var signal = this._readBits(precisionBits + exponentBits, 1, size);
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var exponent = this._readBits(precisionBits, exponentBits, size);
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var significand = 0;
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var divisor = 2;
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// var curByte = length + (-precisionBits >> 3) - 1;
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var curByte = 0;
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do {
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var byteValue = this._readByte(++curByte, size);
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var startBit = precisionBits % 8 || 8;
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var mask = 1 << startBit;
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while (mask >>= 1) {
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if (byteValue & mask) {
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significand += 1 / divisor;
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}
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divisor *= 2;
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}
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} while (precisionBits -= startBit);
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this._pos += size;
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return exponent == (bias << 1) + 1 ? significand ? NaN : signal ? -Infinity : +Infinity
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: (1 + signal * -2) * (exponent || significand ? !exponent ? Math.pow(2, -bias + 1) * significand
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: Math.pow(2, exponent - bias) * (1 + significand) : 0);
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},
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_decodeInt: function(bits, signed){
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var x = this._readBits(0, bits, bits / 8), max = Math.pow(2, bits);
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var result = signed && x >= max / 2 ? x - max : x;
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this._pos += bits / 8;
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return result;
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},
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//shl fix: Henri Torgemane ~1996 (compressed by Jonas Raoni)
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_shl: function (a, b){
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for (++b; --b; a = ((a %= 0x7fffffff + 1) & 0x40000000) == 0x40000000 ? a * 2 : (a - 0x40000000) * 2 + 0x7fffffff + 1);
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return a;
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},
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_readByte: function (i, size) {
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return this._buffer.charCodeAt(this._pos + size - i - 1) & 0xff;
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},
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_readBits: function (start, length, size) {
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var offsetLeft = (start + length) % 8;
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var offsetRight = start % 8;
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var curByte = size - (start >> 3) - 1;
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var lastByte = size + (-(start + length) >> 3);
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var diff = curByte - lastByte;
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var sum = (this._readByte(curByte, size) >> offsetRight) & ((1 << (diff ? 8 - offsetRight : length)) - 1);
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if (diff && offsetLeft) {
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sum += (this._readByte(lastByte++, size) & ((1 << offsetLeft) - 1)) << (diff-- << 3) - offsetRight;
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}
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while (diff) {
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sum += this._shl(this._readByte(lastByte++, size), (diff-- << 3) - offsetRight);
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}
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return sum;
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},
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_checkSize: function (neededBits) {
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if (!(this._pos + Math.ceil(neededBits / 8) < this._buffer.length)) {
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throw new Error("Index out of bound");
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}
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}
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}; |