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Extract duplicate arithmetic decoder to own class

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fkaelberer 2014-03-10 16:56:00 +01:00
parent 5c448135cc
commit 7b5b5178ef
5 changed files with 204 additions and 345 deletions
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158
src/core/jbig2.js
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@ -1,6 +1,5 @@
/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* globals error, shadow */
/* Copyright 2012 Mozilla Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
@ -15,166 +14,11 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* globals ArithmeticDecoder, error, shadow */
'use strict';
var Jbig2Image = (function Jbig2ImageClosure() {
// Annex E. Arithmetic Coding
var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
var QeTable = [
{qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1},
{qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0},
{qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0},
{qe: 0x0AC1, nmps: 4, nlps: 12, switchFlag: 0},
{qe: 0x0521, nmps: 5, nlps: 29, switchFlag: 0},
{qe: 0x0221, nmps: 38, nlps: 33, switchFlag: 0},
{qe: 0x5601, nmps: 7, nlps: 6, switchFlag: 1},
{qe: 0x5401, nmps: 8, nlps: 14, switchFlag: 0},
{qe: 0x4801, nmps: 9, nlps: 14, switchFlag: 0},
{qe: 0x3801, nmps: 10, nlps: 14, switchFlag: 0},
{qe: 0x3001, nmps: 11, nlps: 17, switchFlag: 0},
{qe: 0x2401, nmps: 12, nlps: 18, switchFlag: 0},
{qe: 0x1C01, nmps: 13, nlps: 20, switchFlag: 0},
{qe: 0x1601, nmps: 29, nlps: 21, switchFlag: 0},
{qe: 0x5601, nmps: 15, nlps: 14, switchFlag: 1},
{qe: 0x5401, nmps: 16, nlps: 14, switchFlag: 0},
{qe: 0x5101, nmps: 17, nlps: 15, switchFlag: 0},
{qe: 0x4801, nmps: 18, nlps: 16, switchFlag: 0},
{qe: 0x3801, nmps: 19, nlps: 17, switchFlag: 0},
{qe: 0x3401, nmps: 20, nlps: 18, switchFlag: 0},
{qe: 0x3001, nmps: 21, nlps: 19, switchFlag: 0},
{qe: 0x2801, nmps: 22, nlps: 19, switchFlag: 0},
{qe: 0x2401, nmps: 23, nlps: 20, switchFlag: 0},
{qe: 0x2201, nmps: 24, nlps: 21, switchFlag: 0},
{qe: 0x1C01, nmps: 25, nlps: 22, switchFlag: 0},
{qe: 0x1801, nmps: 26, nlps: 23, switchFlag: 0},
{qe: 0x1601, nmps: 27, nlps: 24, switchFlag: 0},
{qe: 0x1401, nmps: 28, nlps: 25, switchFlag: 0},
{qe: 0x1201, nmps: 29, nlps: 26, switchFlag: 0},
{qe: 0x1101, nmps: 30, nlps: 27, switchFlag: 0},
{qe: 0x0AC1, nmps: 31, nlps: 28, switchFlag: 0},
{qe: 0x09C1, nmps: 32, nlps: 29, switchFlag: 0},
{qe: 0x08A1, nmps: 33, nlps: 30, switchFlag: 0},
{qe: 0x0521, nmps: 34, nlps: 31, switchFlag: 0},
{qe: 0x0441, nmps: 35, nlps: 32, switchFlag: 0},
{qe: 0x02A1, nmps: 36, nlps: 33, switchFlag: 0},
{qe: 0x0221, nmps: 37, nlps: 34, switchFlag: 0},
{qe: 0x0141, nmps: 38, nlps: 35, switchFlag: 0},
{qe: 0x0111, nmps: 39, nlps: 36, switchFlag: 0},
{qe: 0x0085, nmps: 40, nlps: 37, switchFlag: 0},
{qe: 0x0049, nmps: 41, nlps: 38, switchFlag: 0},
{qe: 0x0025, nmps: 42, nlps: 39, switchFlag: 0},
{qe: 0x0015, nmps: 43, nlps: 40, switchFlag: 0},
{qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0},
{qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0},
{qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0},
{qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0}
];
function ArithmeticDecoder(data, start, end) {
this.data = data;
this.bp = start;
this.dataEnd = end;
this.chigh = data[start];
this.clow = 0;
this.byteIn();
this.chigh = ((this.chigh << 7) & 0xFFFF) | ((this.clow >> 9) & 0x7F);
this.clow = (this.clow << 7) & 0xFFFF;
this.ct -= 7;
this.a = 0x8000;
}
ArithmeticDecoder.prototype = {
byteIn: function ArithmeticDecoder_byteIn() {
var data = this.data;
var bp = this.bp;
if (data[bp] == 0xFF) {
var b1 = data[bp + 1];
if (b1 > 0x8F) {
this.clow += 0xFF00;
this.ct = 8;
} else {
bp++;
this.clow += (data[bp] << 9);
this.ct = 7;
this.bp = bp;
}
} else {
bp++;
this.clow += bp < this.dataEnd ? (data[bp] << 8) : 0xFF00;
this.ct = 8;
this.bp = bp;
}
if (this.clow > 0xFFFF) {
this.chigh += (this.clow >> 16);
this.clow &= 0xFFFF;
}
},
readBit: function ArithmeticDecoder_readBit(contexts, pos) {
// contexts are packed into 1 byte:
// highest 7 bits carry cx.index, lowest bit carries cx.mps
var cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
var qeTableIcx = QeTable[cx_index];
var qeIcx = qeTableIcx.qe;
var nmpsIcx = qeTableIcx.nmps;
var nlpsIcx = qeTableIcx.nlps;
var switchIcx = qeTableIcx.switchFlag;
var d;
this.a -= qeIcx;
if (this.chigh < qeIcx) {
// exchangeLps
if (this.a < qeIcx) {
this.a = qeIcx;
d = cx_mps;
cx_index = nmpsIcx;
} else {
this.a = qeIcx;
d = 1 - cx_mps;
if (switchIcx) {
cx_mps = d;
}
cx_index = nlpsIcx;
}
} else {
this.chigh -= qeIcx;
if ((this.a & 0x8000) !== 0) {
return cx_mps;
}
// exchangeMps
if (this.a < qeIcx) {
d = 1 - cx_mps;
if (switchIcx) {
cx_mps = d;
}
cx_index = nlpsIcx;
} else {
d = cx_mps;
cx_index = nmpsIcx;
}
}
// renormD;
do {
if (this.ct === 0) {
this.byteIn();
}
this.a <<= 1;
this.chigh = ((this.chigh << 1) & 0xFFFF) | ((this.clow >> 15) & 1);
this.clow = (this.clow << 1) & 0xFFFF;
this.ct--;
} while ((this.a & 0x8000) === 0);
contexts[pos] = cx_index << 1 | cx_mps;
return d;
}
};
return ArithmeticDecoder;
})();
// Utility data structures
function ContextCache() {}