Convert src/core/arithmetic_decoder.js to ES6 syntax
This commit is contained in:
Tim van der Meij
parent
c967eab8b1
commit
3b637e71d4
@ -12,8 +12,61 @@
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* eslint no-var: error */
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/* This class implements the QM Coder decoding as defined in
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// Table C-2
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const QeTable = [
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{ qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1, },
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{ qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0, },
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{ qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0, },
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{ qe: 0x0AC1, nmps: 4, nlps: 12, switchFlag: 0, },
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{ qe: 0x0521, nmps: 5, nlps: 29, switchFlag: 0, },
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{ qe: 0x0221, nmps: 38, nlps: 33, switchFlag: 0, },
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{ qe: 0x5601, nmps: 7, nlps: 6, switchFlag: 1, },
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{ qe: 0x5401, nmps: 8, nlps: 14, switchFlag: 0, },
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{ qe: 0x4801, nmps: 9, nlps: 14, switchFlag: 0, },
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{ qe: 0x3801, nmps: 10, nlps: 14, switchFlag: 0, },
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{ qe: 0x3001, nmps: 11, nlps: 17, switchFlag: 0, },
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{ qe: 0x2401, nmps: 12, nlps: 18, switchFlag: 0, },
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{ qe: 0x1C01, nmps: 13, nlps: 20, switchFlag: 0, },
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{ qe: 0x1601, nmps: 29, nlps: 21, switchFlag: 0, },
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{ qe: 0x5601, nmps: 15, nlps: 14, switchFlag: 1, },
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{ qe: 0x5401, nmps: 16, nlps: 14, switchFlag: 0, },
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{ qe: 0x5101, nmps: 17, nlps: 15, switchFlag: 0, },
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{ qe: 0x4801, nmps: 18, nlps: 16, switchFlag: 0, },
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{ qe: 0x3801, nmps: 19, nlps: 17, switchFlag: 0, },
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{ qe: 0x3401, nmps: 20, nlps: 18, switchFlag: 0, },
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{ qe: 0x3001, nmps: 21, nlps: 19, switchFlag: 0, },
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{ qe: 0x2801, nmps: 22, nlps: 19, switchFlag: 0, },
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{ qe: 0x2401, nmps: 23, nlps: 20, switchFlag: 0, },
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{ qe: 0x2201, nmps: 24, nlps: 21, switchFlag: 0, },
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{ qe: 0x1C01, nmps: 25, nlps: 22, switchFlag: 0, },
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{ qe: 0x1801, nmps: 26, nlps: 23, switchFlag: 0, },
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{ qe: 0x1601, nmps: 27, nlps: 24, switchFlag: 0, },
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{ qe: 0x1401, nmps: 28, nlps: 25, switchFlag: 0, },
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{ qe: 0x1201, nmps: 29, nlps: 26, switchFlag: 0, },
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{ qe: 0x1101, nmps: 30, nlps: 27, switchFlag: 0, },
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{ qe: 0x0AC1, nmps: 31, nlps: 28, switchFlag: 0, },
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{ qe: 0x09C1, nmps: 32, nlps: 29, switchFlag: 0, },
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{ qe: 0x08A1, nmps: 33, nlps: 30, switchFlag: 0, },
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{ qe: 0x0521, nmps: 34, nlps: 31, switchFlag: 0, },
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{ qe: 0x0441, nmps: 35, nlps: 32, switchFlag: 0, },
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{ qe: 0x02A1, nmps: 36, nlps: 33, switchFlag: 0, },
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{ qe: 0x0221, nmps: 37, nlps: 34, switchFlag: 0, },
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{ qe: 0x0141, nmps: 38, nlps: 35, switchFlag: 0, },
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{ qe: 0x0111, nmps: 39, nlps: 36, switchFlag: 0, },
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{ qe: 0x0085, nmps: 40, nlps: 37, switchFlag: 0, },
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{ qe: 0x0049, nmps: 41, nlps: 38, switchFlag: 0, },
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{ qe: 0x0025, nmps: 42, nlps: 39, switchFlag: 0, },
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{ qe: 0x0015, nmps: 43, nlps: 40, switchFlag: 0, },
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{ qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0, },
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{ qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0, },
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{ qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0, },
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{ qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0, },
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];
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/**
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* This class implements the QM Coder decoding as defined in
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* JPEG 2000 Part I Final Committee Draft Version 1.0
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* Annex C.3 Arithmetic decoding procedure
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* available at http://www.jpeg.org/public/fcd15444-1.pdf
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@ -21,60 +74,9 @@
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* The arithmetic decoder is used in conjunction with context models to decode
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* JPEG2000 and JBIG2 streams.
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*/
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var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
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// Table C-2
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var QeTable = [
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{ qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1, },
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{ qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0, },
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{ qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0, },
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{ qe: 0x0AC1, nmps: 4, nlps: 12, switchFlag: 0, },
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{ qe: 0x0521, nmps: 5, nlps: 29, switchFlag: 0, },
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{ qe: 0x0221, nmps: 38, nlps: 33, switchFlag: 0, },
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{ qe: 0x5601, nmps: 7, nlps: 6, switchFlag: 1, },
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{ qe: 0x5401, nmps: 8, nlps: 14, switchFlag: 0, },
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{ qe: 0x4801, nmps: 9, nlps: 14, switchFlag: 0, },
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{ qe: 0x3801, nmps: 10, nlps: 14, switchFlag: 0, },
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{ qe: 0x3001, nmps: 11, nlps: 17, switchFlag: 0, },
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{ qe: 0x2401, nmps: 12, nlps: 18, switchFlag: 0, },
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{ qe: 0x1C01, nmps: 13, nlps: 20, switchFlag: 0, },
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{ qe: 0x1601, nmps: 29, nlps: 21, switchFlag: 0, },
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{ qe: 0x5601, nmps: 15, nlps: 14, switchFlag: 1, },
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{ qe: 0x5401, nmps: 16, nlps: 14, switchFlag: 0, },
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{ qe: 0x5101, nmps: 17, nlps: 15, switchFlag: 0, },
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{ qe: 0x4801, nmps: 18, nlps: 16, switchFlag: 0, },
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{ qe: 0x3801, nmps: 19, nlps: 17, switchFlag: 0, },
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{ qe: 0x3401, nmps: 20, nlps: 18, switchFlag: 0, },
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{ qe: 0x3001, nmps: 21, nlps: 19, switchFlag: 0, },
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{ qe: 0x2801, nmps: 22, nlps: 19, switchFlag: 0, },
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{ qe: 0x2401, nmps: 23, nlps: 20, switchFlag: 0, },
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{ qe: 0x2201, nmps: 24, nlps: 21, switchFlag: 0, },
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{ qe: 0x1C01, nmps: 25, nlps: 22, switchFlag: 0, },
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{ qe: 0x1801, nmps: 26, nlps: 23, switchFlag: 0, },
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{ qe: 0x1601, nmps: 27, nlps: 24, switchFlag: 0, },
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{ qe: 0x1401, nmps: 28, nlps: 25, switchFlag: 0, },
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{ qe: 0x1201, nmps: 29, nlps: 26, switchFlag: 0, },
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{ qe: 0x1101, nmps: 30, nlps: 27, switchFlag: 0, },
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{ qe: 0x0AC1, nmps: 31, nlps: 28, switchFlag: 0, },
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{ qe: 0x09C1, nmps: 32, nlps: 29, switchFlag: 0, },
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{ qe: 0x08A1, nmps: 33, nlps: 30, switchFlag: 0, },
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{ qe: 0x0521, nmps: 34, nlps: 31, switchFlag: 0, },
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{ qe: 0x0441, nmps: 35, nlps: 32, switchFlag: 0, },
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{ qe: 0x02A1, nmps: 36, nlps: 33, switchFlag: 0, },
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{ qe: 0x0221, nmps: 37, nlps: 34, switchFlag: 0, },
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{ qe: 0x0141, nmps: 38, nlps: 35, switchFlag: 0, },
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{ qe: 0x0111, nmps: 39, nlps: 36, switchFlag: 0, },
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{ qe: 0x0085, nmps: 40, nlps: 37, switchFlag: 0, },
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{ qe: 0x0049, nmps: 41, nlps: 38, switchFlag: 0, },
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{ qe: 0x0025, nmps: 42, nlps: 39, switchFlag: 0, },
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{ qe: 0x0015, nmps: 43, nlps: 40, switchFlag: 0, },
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{ qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0, },
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{ qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0, },
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{ qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0, },
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{ qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0, }
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];
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class ArithmeticDecoder {
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// C.3.5 Initialisation of the decoder (INITDEC)
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function ArithmeticDecoder(data, start, end) {
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constructor(data, start, end) {
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this.data = data;
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this.bp = start;
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this.dataEnd = end;
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@ -90,95 +92,92 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
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this.a = 0x8000;
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}
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ArithmeticDecoder.prototype = {
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// C.3.4 Compressed data input (BYTEIN)
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byteIn: function ArithmeticDecoder_byteIn() {
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var data = this.data;
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var bp = this.bp;
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if (data[bp] === 0xFF) {
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var b1 = data[bp + 1];
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if (b1 > 0x8F) {
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this.clow += 0xFF00;
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this.ct = 8;
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} else {
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bp++;
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this.clow += (data[bp] << 9);
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this.ct = 7;
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this.bp = bp;
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}
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// C.3.4 Compressed data input (BYTEIN)
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byteIn() {
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const data = this.data;
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let bp = this.bp;
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if (data[bp] === 0xFF) {
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if (data[bp + 1] > 0x8F) {
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this.clow += 0xFF00;
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this.ct = 8;
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} else {
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bp++;
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this.clow += bp < this.dataEnd ? (data[bp] << 8) : 0xFF00;
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this.ct = 8;
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this.clow += (data[bp] << 9);
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this.ct = 7;
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this.bp = bp;
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}
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if (this.clow > 0xFFFF) {
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this.chigh += (this.clow >> 16);
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this.clow &= 0xFFFF;
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}
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},
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// C.3.2 Decoding a decision (DECODE)
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readBit: function ArithmeticDecoder_readBit(contexts, pos) {
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// contexts are packed into 1 byte:
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// highest 7 bits carry cx.index, lowest bit carries cx.mps
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var cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
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var qeTableIcx = QeTable[cx_index];
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var qeIcx = qeTableIcx.qe;
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var d;
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var a = this.a - qeIcx;
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} else {
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bp++;
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this.clow += bp < this.dataEnd ? (data[bp] << 8) : 0xFF00;
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this.ct = 8;
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this.bp = bp;
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}
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if (this.clow > 0xFFFF) {
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this.chigh += (this.clow >> 16);
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this.clow &= 0xFFFF;
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}
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}
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if (this.chigh < qeIcx) {
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// exchangeLps
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if (a < qeIcx) {
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a = qeIcx;
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d = cx_mps;
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cx_index = qeTableIcx.nmps;
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} else {
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a = qeIcx;
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d = 1 ^ cx_mps;
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if (qeTableIcx.switchFlag === 1) {
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cx_mps = d;
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}
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cx_index = qeTableIcx.nlps;
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}
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// C.3.2 Decoding a decision (DECODE)
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readBit(contexts, pos) {
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// Contexts are packed into 1 byte:
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// highest 7 bits carry cx.index, lowest bit carries cx.mps
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let cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
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const qeTableIcx = QeTable[cx_index];
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const qeIcx = qeTableIcx.qe;
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let d;
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let a = this.a - qeIcx;
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if (this.chigh < qeIcx) {
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// exchangeLps
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if (a < qeIcx) {
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a = qeIcx;
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d = cx_mps;
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cx_index = qeTableIcx.nmps;
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} else {
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this.chigh -= qeIcx;
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if ((a & 0x8000) !== 0) {
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this.a = a;
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return cx_mps;
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}
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// exchangeMps
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if (a < qeIcx) {
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d = 1 ^ cx_mps;
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if (qeTableIcx.switchFlag === 1) {
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cx_mps = d;
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}
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cx_index = qeTableIcx.nlps;
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} else {
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d = cx_mps;
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cx_index = qeTableIcx.nmps;
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a = qeIcx;
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d = 1 ^ cx_mps;
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if (qeTableIcx.switchFlag === 1) {
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cx_mps = d;
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}
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cx_index = qeTableIcx.nlps;
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}
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// C.3.3 renormD;
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do {
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if (this.ct === 0) {
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this.byteIn();
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} else {
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this.chigh -= qeIcx;
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if ((a & 0x8000) !== 0) {
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this.a = a;
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return cx_mps;
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}
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// exchangeMps
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if (a < qeIcx) {
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d = 1 ^ cx_mps;
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if (qeTableIcx.switchFlag === 1) {
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cx_mps = d;
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}
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cx_index = qeTableIcx.nlps;
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} else {
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d = cx_mps;
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cx_index = qeTableIcx.nmps;
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}
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}
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// C.3.3 renormD;
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do {
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if (this.ct === 0) {
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this.byteIn();
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}
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a <<= 1;
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this.chigh = ((this.chigh << 1) & 0xFFFF) | ((this.clow >> 15) & 1);
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this.clow = (this.clow << 1) & 0xFFFF;
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this.ct--;
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} while ((a & 0x8000) === 0);
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this.a = a;
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a <<= 1;
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this.chigh = ((this.chigh << 1) & 0xFFFF) | ((this.clow >> 15) & 1);
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this.clow = (this.clow << 1) & 0xFFFF;
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this.ct--;
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} while ((a & 0x8000) === 0);
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this.a = a;
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contexts[pos] = cx_index << 1 | cx_mps;
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return d;
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},
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};
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return ArithmeticDecoder;
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})();
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contexts[pos] = cx_index << 1 | cx_mps;
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return d;
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}
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}
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export {
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ArithmeticDecoder,
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