luhn-generator
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A generator of numbers that passes the validation of Luhn algorithm or Luhn formula, also known as the 'modulus 10' or 'mod 10' algorithm
142 lines (115 loc) • 4.07 kB
JavaScript
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);