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Convert src/core/arithmetic_decoder.js to ES6 syntax

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Tim van der Meij 2019-01-05 18:51:37 +01:00
parent c967eab8b1
commit 3b637e71d4
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1 changed files with 131 additions and 132 deletions
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src/core/arithmetic_decoder.js
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@ -12,18 +12,10 @@
* See the License for the specific language governing permissions and * See the License for the specific language governing permissions and
* limitations under the License. * limitations under the License.
*/ */
/* eslint no-var: error */
/* This class implements the QM Coder decoding as defined in
* JPEG 2000 Part I Final Committee Draft Version 1.0
* Annex C.3 Arithmetic decoding procedure
* available at http://www.jpeg.org/public/fcd15444-1.pdf
*
* The arithmetic decoder is used in conjunction with context models to decode
* JPEG2000 and JBIG2 streams.
*/
var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
// Table C-2 // Table C-2
var QeTable = [ const QeTable = [
{ qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1, }, { qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1, },
{ qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0, }, { qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0, },
{ qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0, }, { qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0, },
@ -70,11 +62,21 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
{ qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0, }, { qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0, },
{ qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0, }, { qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0, },
{ qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0, }, { qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0, },
{ qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0, } { qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0, },
]; ];
/**
* This class implements the QM Coder decoding as defined in
* JPEG 2000 Part I Final Committee Draft Version 1.0
* Annex C.3 Arithmetic decoding procedure
* available at http://www.jpeg.org/public/fcd15444-1.pdf
*
* The arithmetic decoder is used in conjunction with context models to decode
* JPEG2000 and JBIG2 streams.
*/
class ArithmeticDecoder {
// C.3.5 Initialisation of the decoder (INITDEC) // C.3.5 Initialisation of the decoder (INITDEC)
function ArithmeticDecoder(data, start, end) { constructor(data, start, end) {
this.data = data; this.data = data;
this.bp = start; this.bp = start;
this.dataEnd = end; this.dataEnd = end;
@ -90,14 +92,13 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
this.a = 0x8000; this.a = 0x8000;
} }
ArithmeticDecoder.prototype = {
// C.3.4 Compressed data input (BYTEIN) // C.3.4 Compressed data input (BYTEIN)
byteIn: function ArithmeticDecoder_byteIn() { byteIn() {
var data = this.data; const data = this.data;
var bp = this.bp; let bp = this.bp;
if (data[bp] === 0xFF) { if (data[bp] === 0xFF) {
var b1 = data[bp + 1]; if (data[bp + 1] > 0x8F) {
if (b1 > 0x8F) {
this.clow += 0xFF00; this.clow += 0xFF00;
this.ct = 8; this.ct = 8;
} else { } else {
@ -116,16 +117,17 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
this.chigh += (this.clow >> 16); this.chigh += (this.clow >> 16);
this.clow &= 0xFFFF; this.clow &= 0xFFFF;
} }
}, }
// C.3.2 Decoding a decision (DECODE) // C.3.2 Decoding a decision (DECODE)
readBit: function ArithmeticDecoder_readBit(contexts, pos) { readBit(contexts, pos) {
// contexts are packed into 1 byte: // Contexts are packed into 1 byte:
// highest 7 bits carry cx.index, lowest bit carries cx.mps // highest 7 bits carry cx.index, lowest bit carries cx.mps
var cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1; let cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
var qeTableIcx = QeTable[cx_index]; const qeTableIcx = QeTable[cx_index];
var qeIcx = qeTableIcx.qe; const qeIcx = qeTableIcx.qe;
var d; let d;
var a = this.a - qeIcx; let a = this.a - qeIcx;
if (this.chigh < qeIcx) { if (this.chigh < qeIcx) {
// exchangeLps // exchangeLps
@ -174,11 +176,8 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
contexts[pos] = cx_index << 1 | cx_mps; contexts[pos] = cx_index << 1 | cx_mps;
return d; return d;
}, }
}; }
return ArithmeticDecoder;
})();
export { export {
ArithmeticDecoder, ArithmeticDecoder,