Updated config_spec.ini to add %(data_basedir)s and make use of it!
[mediagoblin.git] / extlib / thingiview.js / binaryReader.js
1 // BinaryReader
2 // Refactored by Vjeux <vjeuxx@gmail.com>
3 // http://blog.vjeux.com/2010/javascript/javascript-binary-reader.html
4
5 // Original
6 //+ Jonas Raoni Soares Silva
7 //@ http://jsfromhell.com/classes/binary-parser [rev. #1]
8
9 BinaryReader = function (data) {
10 this._buffer = data;
11 this._pos = 0;
12 };
13
14 BinaryReader.prototype = {
15
16 /* Public */
17
18 readInt8: function (){ return this._decodeInt(8, true); },
19 readUInt8: function (){ return this._decodeInt(8, false); },
20 readInt16: function (){ return this._decodeInt(16, true); },
21 readUInt16: function (){ return this._decodeInt(16, false); },
22 readInt32: function (){ return this._decodeInt(32, true); },
23 readUInt32: function (){ return this._decodeInt(32, false); },
24
25 readFloat: function (){ return this._decodeFloat(23, 8); },
26 readDouble: function (){ return this._decodeFloat(52, 11); },
27
28 readChar: function () { return this.readString(1); },
29 readString: function (length) {
30 this._checkSize(length * 8);
31 var result = this._buffer.substr(this._pos, length);
32 this._pos += length;
33 return result;
34 },
35
36 seek: function (pos) {
37 this._pos = pos;
38 this._checkSize(0);
39 },
40
41 getPosition: function () {
42 return this._pos;
43 },
44
45 getSize: function () {
46 return this._buffer.length;
47 },
48
49
50 /* Private */
51
52 _decodeFloat: function(precisionBits, exponentBits){
53 var length = precisionBits + exponentBits + 1;
54 var size = length >> 3;
55 this._checkSize(length);
56
57 var bias = Math.pow(2, exponentBits - 1) - 1;
58 var signal = this._readBits(precisionBits + exponentBits, 1, size);
59 var exponent = this._readBits(precisionBits, exponentBits, size);
60 var significand = 0;
61 var divisor = 2;
62 // var curByte = length + (-precisionBits >> 3) - 1;
63 var curByte = 0;
64 do {
65 var byteValue = this._readByte(++curByte, size);
66 var startBit = precisionBits % 8 || 8;
67 var mask = 1 << startBit;
68 while (mask >>= 1) {
69 if (byteValue & mask) {
70 significand += 1 / divisor;
71 }
72 divisor *= 2;
73 }
74 } while (precisionBits -= startBit);
75
76 this._pos += size;
77
78 return exponent == (bias << 1) + 1 ? significand ? NaN : signal ? -Infinity : +Infinity
79 : (1 + signal * -2) * (exponent || significand ? !exponent ? Math.pow(2, -bias + 1) * significand
80 : Math.pow(2, exponent - bias) * (1 + significand) : 0);
81 },
82
83 _decodeInt: function(bits, signed){
84 var x = this._readBits(0, bits, bits / 8), max = Math.pow(2, bits);
85 var result = signed && x >= max / 2 ? x - max : x;
86
87 this._pos += bits / 8;
88 return result;
89 },
90
91 //shl fix: Henri Torgemane ~1996 (compressed by Jonas Raoni)
92 _shl: function (a, b){
93 for (++b; --b; a = ((a %= 0x7fffffff + 1) & 0x40000000) == 0x40000000 ? a * 2 : (a - 0x40000000) * 2 + 0x7fffffff + 1);
94 return a;
95 },
96
97 _readByte: function (i, size) {
98 return this._buffer.charCodeAt(this._pos + size - i - 1) & 0xff;
99 },
100
101 _readBits: function (start, length, size) {
102 var offsetLeft = (start + length) % 8;
103 var offsetRight = start % 8;
104 var curByte = size - (start >> 3) - 1;
105 var lastByte = size + (-(start + length) >> 3);
106 var diff = curByte - lastByte;
107
108 var sum = (this._readByte(curByte, size) >> offsetRight) & ((1 << (diff ? 8 - offsetRight : length)) - 1);
109
110 if (diff && offsetLeft) {
111 sum += (this._readByte(lastByte++, size) & ((1 << offsetLeft) - 1)) << (diff-- << 3) - offsetRight;
112 }
113
114 while (diff) {
115 sum += this._shl(this._readByte(lastByte++, size), (diff-- << 3) - offsetRight);
116 }
117
118 return sum;
119 },
120
121 _checkSize: function (neededBits) {
122 if (!(this._pos + Math.ceil(neededBits / 8) < this._buffer.length)) {
123 throw new Error("Index out of bound");
124 }
125 }
126 };