143 lines
3.8 KiB
TypeScript
143 lines
3.8 KiB
TypeScript
import { Context, Recogniser } from '.';
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import match, { Match } from '../match';
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/**
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* This is a superclass for the individual detectors for
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* each of the detectable members of the ISO 2022 family
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* of encodings.
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*/
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class ISO_2022 implements Recogniser {
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escapeSequences: number[][] = [];
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name() {
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return 'ISO_2022';
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}
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match(det: Context): Match | null {
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/**
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* Matching function shared among the 2022 detectors JP, CN and KR
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* Counts up the number of legal an unrecognized escape sequences in
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* the sample of text, and computes a score based on the total number &
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* the proportion that fit the encoding.
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*
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*
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* @param text the byte buffer containing text to analyse
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* @param textLen the size of the text in the byte.
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* @param escapeSequences the byte escape sequences to test for.
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* @return match quality, in the range of 0-100.
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*/
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let i, j;
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let escN;
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let hits = 0;
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let misses = 0;
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let shifts = 0;
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let confidence;
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// TODO: refactor me
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const text = det.inputBytes;
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const textLen = det.inputLen;
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scanInput: for (i = 0; i < textLen; i++) {
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if (text[i] == 0x1b) {
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checkEscapes: for (
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escN = 0;
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escN < this.escapeSequences.length;
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escN++
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) {
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const seq = this.escapeSequences[escN];
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if (textLen - i < seq.length) continue checkEscapes;
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for (j = 1; j < seq.length; j++)
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if (seq[j] != text[i + j]) continue checkEscapes;
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hits++;
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i += seq.length - 1;
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continue scanInput;
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}
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misses++;
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}
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// Shift in/out
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if (text[i] == 0x0e || text[i] == 0x0f) shifts++;
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}
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if (hits == 0) return null;
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//
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// Initial quality is based on relative proportion of recognized vs.
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// unrecognized escape sequences.
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// All good: quality = 100;
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// half or less good: quality = 0;
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// linear in between.
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confidence = (100 * hits - 100 * misses) / (hits + misses);
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// Back off quality if there were too few escape sequences seen.
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// Include shifts in this computation, so that KR does not get penalized
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// for having only a single Escape sequence, but many shifts.
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if (hits + shifts < 5) confidence -= (5 - (hits + shifts)) * 10;
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return confidence <= 0 ? null : match(det, this, confidence);
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}
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}
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export class ISO_2022_JP extends ISO_2022 {
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name() {
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return 'ISO-2022-JP';
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}
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language() {
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return 'ja';
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}
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escapeSequences = [
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[0x1b, 0x24, 0x28, 0x43], // KS X 1001:1992
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[0x1b, 0x24, 0x28, 0x44], // JIS X 212-1990
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[0x1b, 0x24, 0x40], // JIS C 6226-1978
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[0x1b, 0x24, 0x41], // GB 2312-80
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[0x1b, 0x24, 0x42], // JIS X 208-1983
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[0x1b, 0x26, 0x40], // JIS X 208 1990, 1997
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[0x1b, 0x28, 0x42], // ASCII
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[0x1b, 0x28, 0x48], // JIS-Roman
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[0x1b, 0x28, 0x49], // Half-width katakana
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[0x1b, 0x28, 0x4a], // JIS-Roman
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[0x1b, 0x2e, 0x41], // ISO 8859-1
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[0x1b, 0x2e, 0x46], // ISO 8859-7
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];
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}
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export class ISO_2022_KR extends ISO_2022 {
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name() {
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return 'ISO-2022-KR';
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}
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language() {
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return 'kr';
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}
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escapeSequences = [[0x1b, 0x24, 0x29, 0x43]];
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}
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export class ISO_2022_CN extends ISO_2022 {
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name() {
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return 'ISO-2022-CN';
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}
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language() {
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return 'zh';
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}
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escapeSequences = [
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[0x1b, 0x24, 0x29, 0x41], // GB 2312-80
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[0x1b, 0x24, 0x29, 0x47], // CNS 11643-1992 Plane 1
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[0x1b, 0x24, 0x2a, 0x48], // CNS 11643-1992 Plane 2
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[0x1b, 0x24, 0x29, 0x45], // ISO-IR-165
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[0x1b, 0x24, 0x2b, 0x49], // CNS 11643-1992 Plane 3
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[0x1b, 0x24, 0x2b, 0x4a], // CNS 11643-1992 Plane 4
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[0x1b, 0x24, 0x2b, 0x4b], // CNS 11643-1992 Plane 5
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[0x1b, 0x24, 0x2b, 0x4c], // CNS 11643-1992 Plane 6
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[0x1b, 0x24, 0x2b, 0x4d], // CNS 11643-1992 Plane 7
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[0x1b, 0x4e], // SS2
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[0x1b, 0x4f], // SS3
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];
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}
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