forked from Supositware/Haha-Yes
89 lines
2.5 KiB
JavaScript
89 lines
2.5 KiB
JavaScript
/*
|
|
node-bzip - a pure-javascript Node.JS module for decoding bzip2 data
|
|
|
|
Copyright (C) 2012 Eli Skeggs
|
|
|
|
This library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
This library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with this library; if not, see
|
|
http://www.gnu.org/licenses/lgpl-2.1.html
|
|
|
|
Adapted from bzip2.js, copyright 2011 antimatter15 (antimatter15@gmail.com).
|
|
|
|
Based on micro-bunzip by Rob Landley (rob@landley.net).
|
|
|
|
Based on bzip2 decompression code by Julian R Seward (jseward@acm.org),
|
|
which also acknowledges contributions by Mike Burrows, David Wheeler,
|
|
Peter Fenwick, Alistair Moffat, Radford Neal, Ian H. Witten,
|
|
Robert Sedgewick, and Jon L. Bentley.
|
|
*/
|
|
|
|
var BITMASK = [0x00, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
|
|
|
|
// offset in bytes
|
|
var BitReader = function(stream) {
|
|
this.stream = stream;
|
|
this.bitOffset = 0;
|
|
this.curByte = 0;
|
|
this.hasByte = false;
|
|
};
|
|
|
|
BitReader.prototype._ensureByte = function() {
|
|
if (!this.hasByte) {
|
|
this.curByte = this.stream.readByte();
|
|
this.hasByte = true;
|
|
}
|
|
};
|
|
|
|
// reads bits from the buffer
|
|
BitReader.prototype.read = function(bits) {
|
|
var result = 0;
|
|
while (bits > 0) {
|
|
this._ensureByte();
|
|
var remaining = 8 - this.bitOffset;
|
|
// if we're in a byte
|
|
if (bits >= remaining) {
|
|
result <<= remaining;
|
|
result |= BITMASK[remaining] & this.curByte;
|
|
this.hasByte = false;
|
|
this.bitOffset = 0;
|
|
bits -= remaining;
|
|
} else {
|
|
result <<= bits;
|
|
var shift = remaining - bits;
|
|
result |= (this.curByte & (BITMASK[bits] << shift)) >> shift;
|
|
this.bitOffset += bits;
|
|
bits = 0;
|
|
}
|
|
}
|
|
return result;
|
|
};
|
|
|
|
// seek to an arbitrary point in the buffer (expressed in bits)
|
|
BitReader.prototype.seek = function(pos) {
|
|
var n_bit = pos % 8;
|
|
var n_byte = (pos - n_bit) / 8;
|
|
this.bitOffset = n_bit;
|
|
this.stream.seek(n_byte);
|
|
this.hasByte = false;
|
|
};
|
|
|
|
// reads 6 bytes worth of data using the read method
|
|
BitReader.prototype.pi = function() {
|
|
var buf = new Buffer(6), i;
|
|
for (i = 0; i < buf.length; i++) {
|
|
buf[i] = this.read(8);
|
|
}
|
|
return buf.toString('hex');
|
|
};
|
|
|
|
module.exports = BitReader;
|