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/*
*******************************************************************************
* Copyright (C) 2005 - 2008, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*/
package org.apache.tika.parser.txt;
/**
* class CharsetRecog_2022 part of the ICU charset detection imlementation.
* This is a superclass for the individual detectors for
* each of the detectable members of the ISO 2022 family
* of encodings.
*
* The separate classes are nested within this class.
*
* @internal
*/
abstract class CharsetRecog_2022 extends CharsetRecognizer {
/**
* 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.
*/
int match(byte[] text, int textLen, byte[][] escapeSequences) {
int i, j;
int escN;
int hits = 0;
int misses = 0;
int shifts = 0;
int quality;
scanInput:
for (i = 0; i < textLen; i++) {
if (text[i] == 0x1b) {
checkEscapes:
for (escN = 0; escN < escapeSequences.length; escN++) {
byte[] seq = 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++;
}
if (text[i] == 0x0e || text[i] == 0x0f) {
// Shift in/out
shifts++;
}
}
if (hits == 0) {
return 0;
}
//
// 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;
}
if (quality < 0) {
quality = 0;
}
return quality;
}
static class CharsetRecog_2022JP extends CharsetRecog_2022 {
private byte[][] 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
};
String getName() {
return "ISO-2022-JP";
}
int match(CharsetDetector det) {
return match(det.fInputBytes, det.fInputLen, escapeSequences);
}
}
static class CharsetRecog_2022KR extends CharsetRecog_2022 {
private byte[][] escapeSequences = {
{0x1b, 0x24, 0x29, 0x43}
};
String getName() {
return "ISO-2022-KR";
}
int match(CharsetDetector det) {
return match(det.fInputBytes, det.fInputLen, escapeSequences);
}
}
static class CharsetRecog_2022CN extends CharsetRecog_2022 {
private byte[][] 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
};
String getName() {
return "ISO-2022-CN";
}
int match(CharsetDetector det) {
return match(det.fInputBytes, det.fInputLen, escapeSequences);
}
}
}
