| 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); |