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util.js
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util.js
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var levels = new Object();
function BitStream(data) {
this.data = data;
this.pos = 0;
this.bitsLeftInByte = 0;
this.nextByte = 0;
dp("BitStream dump\n");
for (var i = 0; i < this.data.length; i++) {
dp(this.data[i] + "\n");
}
}
BitStream.prototype.getInt32 = function() {
var r = 0;
r += this.getByte() << 24;
r += this.getByte() << 16;
r += this.getByte() << 8;
r += this.getByte();
return r;
};
BitStream.prototype.getString = function(i) {
var s = '';
while(i != 0) {
s += String.fromCharCode(this.getByte());
i--;
}
return s;
};
BitStream.prototype.getByte = function() {
return this.getBits(8);
};
BitStream.prototype.getBit = function() {
if (this.bitsLeftInByte == 0) {
if (this.pos >= this.data.length) {
throw "Array bounds";
}
this.nextByte = this.data[this.pos];
this.pos++;
this.bitsLeftInByte = 8;
}
var b = (this.nextByte & 128) == 128;
this.nextByte <<= 1;
this.bitsLeftInByte--;
return b;
};
BitStream.prototype.getBits = function(bits) {
var bb = 0;
dp("getBits: bits: " + bits);
while(bits > 0) {
bb <<= 1;
if (this.getBit()) {
bb++;
}
bits--;
}
dp(" " + bb.toString(16) + "\n");
return bb;
};
BitStream.prototype.getRestOfByte = function() {
return this.getBits(this.bitsLeftInByte);
};
BitStream.prototype.eof = function() {
return (this.bitsLeftInByte == 0) && (this.pos >= this.data.length);
};
function rleDecode(stm, len) {
var result = new Array(len);
// number of bytes to represent one integer
var bytecount = stm.getByte();
var bits;
var framebits = 8;
if ((bytecount & 128) == 128) {
if ((bytecount & 64) == 64) {
framebits = stm.getBits(5);
}
bits = bytecount & 63;
} else {
if (bytecount > 4) {
throw "Bad file bytecount";
}
bits = bytecount * 8;
}
dp("bits: " + bits + ", bytecount: " + bytecount + ", framebits: " + framebits + "\n");
var run;
var ri = 0;
while (ri < len) {
run = stm.getBits(framebits);
var ch;
if (run == 0) {
// anti-run
run = stm.getBits(framebits);
dp("skipping " + run + ": ");
for (var i = 0; i < run; i++) {
ch = stm.getBits(bits);
dp(ch + " ");
result[ri++] = ch;
}
dp("\n");
} else {
// run
ch = stm.getBits(bits);
dp(run + " " + ch + "'s: ");
for (var i = 0; i < run; i++) {
dp(ch + " ");
result[ri++] = ch;
}
dp("\n");
}
}
stm.getRestOfByte();
return result;
}
function dp(p) {
return;
var d = document.getElementById("debug");
if (d.firstChild == null) {
d.appendChild(document.createTextNode(p));
} else {
d.firstChild.appendData(p);
}
}