var util = require('util'),
|
Match = require ('../match');
|
|
|
/**
|
* This is a superclass for the individual detectors for
|
* each of the detectable members of the ISO 2022 family
|
* of encodings.
|
*/
|
|
function ISO_2022() {}
|
|
ISO_2022.prototype.match = function(det) {
|
|
/**
|
* Matching function shared among the 2022 detectors JP, CN and KR
|
* Counts up the number of legal an unrecognized escape sequences in
|
* the sample of text, and computes a score based on the total number &
|
* the proportion that fit the encoding.
|
*
|
*
|
* @param text the byte buffer containing text to analyse
|
* @param textLen the size of the text in the byte.
|
* @param escapeSequences the byte escape sequences to test for.
|
* @return match quality, in the range of 0-100.
|
*/
|
|
var i, j;
|
var escN;
|
var hits = 0;
|
var misses = 0;
|
var shifts = 0;
|
var quality;
|
|
// TODO: refactor me
|
var text = det.fInputBytes;
|
var textLen = det.fInputLen;
|
|
scanInput:
|
for (i = 0; i < textLen; i++) {
|
if (text[i] == 0x1b) {
|
checkEscapes:
|
for (escN = 0; escN < this.escapeSequences.length; escN++) {
|
var seq = this.escapeSequences[escN];
|
|
if ((textLen - i) < seq.length)
|
continue checkEscapes;
|
|
for (j = 1; j < seq.length; j++)
|
if (seq[j] != text[i + j])
|
continue checkEscapes;
|
|
|
hits++;
|
i += seq.length - 1;
|
continue scanInput;
|
}
|
|
misses++;
|
}
|
|
// Shift in/out
|
if (text[i] == 0x0e || text[i] == 0x0f)
|
shifts++;
|
|
}
|
|
if (hits == 0)
|
return null;
|
|
//
|
// Initial quality is based on relative proportion of recongized vs.
|
// unrecognized escape sequences.
|
// All good: quality = 100;
|
// half or less good: quality = 0;
|
// linear inbetween.
|
quality = (100 * hits - 100 * misses) / (hits + misses);
|
|
// Back off quality if there were too few escape sequences seen.
|
// Include shifts in this computation, so that KR does not get penalized
|
// for having only a single Escape sequence, but many shifts.
|
if (hits + shifts < 5)
|
quality -= (5 - (hits + shifts)) * 10;
|
|
return quality <= 0 ? null : new Match(det, this, quality);
|
};
|
|
module.exports.ISO_2022_JP = function() {
|
this.name = function() {
|
return 'ISO-2022-JP';
|
};
|
this.escapeSequences = [
|
[ 0x1b, 0x24, 0x28, 0x43 ], // KS X 1001:1992
|
[ 0x1b, 0x24, 0x28, 0x44 ], // JIS X 212-1990
|
[ 0x1b, 0x24, 0x40 ], // JIS C 6226-1978
|
[ 0x1b, 0x24, 0x41 ], // GB 2312-80
|
[ 0x1b, 0x24, 0x42 ], // JIS X 208-1983
|
[ 0x1b, 0x26, 0x40 ], // JIS X 208 1990, 1997
|
[ 0x1b, 0x28, 0x42 ], // ASCII
|
[ 0x1b, 0x28, 0x48 ], // JIS-Roman
|
[ 0x1b, 0x28, 0x49 ], // Half-width katakana
|
[ 0x1b, 0x28, 0x4a ], // JIS-Roman
|
[ 0x1b, 0x2e, 0x41 ], // ISO 8859-1
|
[ 0x1b, 0x2e, 0x46 ] // ISO 8859-7
|
];
|
};
|
util.inherits(module.exports.ISO_2022_JP, ISO_2022);
|
|
|
|
module.exports.ISO_2022_KR = function() {
|
this.name = function() {
|
return 'ISO-2022-KR';
|
};
|
this.escapeSequences = [
|
[ 0x1b, 0x24, 0x29, 0x43 ]
|
];
|
};
|
util.inherits(module.exports.ISO_2022_KR, ISO_2022);
|
|
|
|
module.exports.ISO_2022_CN = function() {
|
this.name = function() {
|
return 'ISO-2022-CN';
|
};
|
this.escapeSequences = [
|
[ 0x1b, 0x24, 0x29, 0x41 ], // GB 2312-80
|
[ 0x1b, 0x24, 0x29, 0x47 ], // CNS 11643-1992 Plane 1
|
[ 0x1b, 0x24, 0x2A, 0x48 ], // CNS 11643-1992 Plane 2
|
[ 0x1b, 0x24, 0x29, 0x45 ], // ISO-IR-165
|
[ 0x1b, 0x24, 0x2B, 0x49 ], // CNS 11643-1992 Plane 3
|
[ 0x1b, 0x24, 0x2B, 0x4A ], // CNS 11643-1992 Plane 4
|
[ 0x1b, 0x24, 0x2B, 0x4B ], // CNS 11643-1992 Plane 5
|
[ 0x1b, 0x24, 0x2B, 0x4C ], // CNS 11643-1992 Plane 6
|
[ 0x1b, 0x24, 0x2B, 0x4D ], // CNS 11643-1992 Plane 7
|
[ 0x1b, 0x4e ], // SS2
|
[ 0x1b, 0x4f ] // SS3
|
];
|
};
|
util.inherits(module.exports.ISO_2022_CN, ISO_2022);
|
