142 lines
4.0 KiB
JavaScript
142 lines
4.0 KiB
JavaScript
var util = require('util'),
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Match = require ('../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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function ISO_2022() {}
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ISO_2022.prototype.match = function(det) {
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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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var i, j;
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var escN;
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var hits = 0;
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var misses = 0;
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var shifts = 0;
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var quality;
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// TODO: refactor me
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var text = det.fInputBytes;
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var textLen = det.fInputLen;
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scanInput:
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for (i = 0; i < textLen; i++) {
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if (text[i] == 0x1b) {
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checkEscapes:
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for (escN = 0; escN < this.escapeSequences.length; escN++) {
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var seq = this.escapeSequences[escN];
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if ((textLen - i) < seq.length)
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continue checkEscapes;
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for (j = 1; j < seq.length; j++)
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if (seq[j] != text[i + j])
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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)
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shifts++;
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}
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if (hits == 0)
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return null;
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//
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// Initial quality is based on relative proportion of recongized 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 inbetween.
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quality = (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)
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quality -= (5 - (hits + shifts)) * 10;
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return quality <= 0 ? null : new Match(det, this, quality);
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};
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module.exports.ISO_2022_JP = function() {
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this.name = function() {
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return 'ISO-2022-JP';
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};
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this.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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util.inherits(module.exports.ISO_2022_JP, ISO_2022);
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module.exports.ISO_2022_KR = function() {
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this.name = function() {
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return 'ISO-2022-KR';
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};
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this.escapeSequences = [
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[ 0x1b, 0x24, 0x29, 0x43 ]
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];
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};
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util.inherits(module.exports.ISO_2022_KR, ISO_2022);
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module.exports.ISO_2022_CN = function() {
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this.name = function() {
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return 'ISO-2022-CN';
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};
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this.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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util.inherits(module.exports.ISO_2022_CN, ISO_2022);
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