icuSources/i18n/csr2022.cpp

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3 /*
   4  **********************************************************************
   5  *   Copyright (C) 2005-2016, International Business Machines
   6  *   Corporation and others.  All Rights Reserved.
   7  **********************************************************************
   8  */
   9
  10 #include "unicode/utypes.h"
  11
  12 #if !UCONFIG_NO_CONVERSION
  13
  14 #include "cmemory.h"
  15 #include "cstring.h"
  16
  17 #include "csr2022.h"
  18 #include "csmatch.h"
  19
  20 U_NAMESPACE_BEGIN
  21
  22 /**
  23  * Matching function shared among the 2022 detectors JP, CN and KR
  24  * Counts up the number of legal and unrecognized escape sequences in
  25  * the sample of text, and computes a score based on the total number &
  26  * the proportion that fit the encoding.
  27  *
  28  *
  29  * @param text the byte buffer containing text to analyse
  30  * @param textLen  the size of the text in the byte.
  31  * @param escapeSequences the byte escape sequences to test for.
  32  * @return match quality, in the range of 0-100.
  33  */
  34 int32_t CharsetRecog_2022::match_2022(const uint8_t *text, int32_t textLen, const uint8_t escapeSequences[][5], int32_t escapeSequences_length) const
  35 {
  36     int32_t i, j;
  37     int32_t escN;
  38     int32_t hits   = 0;
  39     int32_t misses = 0;
  40     int32_t shifts = 0;
  41     int32_t quality;
  42
  43     i = 0;
  44     while(i < textLen) {
  45         if(text[i] == 0x1B) {
  46             escN = 0;
  47             while(escN < escapeSequences_length) {
  48                 const uint8_t *seq = escapeSequences[escN];
  49                 int32_t seq_length = (int32_t)uprv_strlen((const char *) seq);
  50
  51                 if (textLen-i >= seq_length) {
  52                     j = 1;
  53                     while(j < seq_length) {
  54                         if(seq[j] != text[i+j]) {
  55                             goto checkEscapes;
  56                         }
  57
  58                         j += 1;
  59                     }
  60
  61                     hits += 1;
  62                     i += seq_length-1;
  63                     goto scanInput;
  64                 }
  65                 // else we ran out of string to compare this time.
  66 checkEscapes:
  67                 escN += 1;
  68             }
  69
  70             misses += 1;
  71         }
  72
  73         if( text[i]== 0x0e || text[i] == 0x0f){
  74             shifts += 1;
  75         }
  76
  77 scanInput:
  78         i += 1;
  79     }
  80
  81     if (hits == 0) {
  82         return 0;
  83     }
  84
  85     //
  86     // Initial quality is based on relative proportion of recongized vs.
  87     //   unrecognized escape sequences.
  88     //   All good:  quality = 100;
  89     //   half or less good: quality = 0;
  90     //   linear inbetween.
  91     quality = (100*hits - 100*misses) / (hits + misses);
  92
  93     // Back off quality if there were too few escape sequences seen.
  94     //   Include shifts in this computation, so that KR does not get penalized
  95     //   for having only a single Escape sequence, but many shifts.
  96     if (hits+shifts < 5) {
  97         quality -= (5-(hits+shifts))*10;
  98     }
  99
 100     if (quality < 0) {
 101         quality = 0;
 102     }
 103
 104     return quality;
 105 }
 106
 107
 108 static const uint8_t escapeSequences_2022JP[][5] = {
 109     {0x1b, 0x24, 0x28, 0x43, 0x00},   // KS X 1001:1992
 110     {0x1b, 0x24, 0x28, 0x44, 0x00},   // JIS X 212-1990
 111     {0x1b, 0x24, 0x40, 0x00, 0x00},   // JIS C 6226-1978
 112     {0x1b, 0x24, 0x41, 0x00, 0x00},   // GB 2312-80
 113     {0x1b, 0x24, 0x42, 0x00, 0x00},   // JIS X 208-1983
 114     {0x1b, 0x26, 0x40, 0x00, 0x00},   // JIS X 208 1990, 1997
 115     {0x1b, 0x28, 0x42, 0x00, 0x00},   // ASCII
 116     {0x1b, 0x28, 0x48, 0x00, 0x00},   // JIS-Roman
 117     {0x1b, 0x28, 0x49, 0x00, 0x00},   // Half-width katakana
 118     {0x1b, 0x28, 0x4a, 0x00, 0x00},   // JIS-Roman
 119     {0x1b, 0x2e, 0x41, 0x00, 0x00},   // ISO 8859-1
 120     {0x1b, 0x2e, 0x46, 0x00, 0x00}    // ISO 8859-7
 121 };
 122
 123 #if !UCONFIG_ONLY_HTML_CONVERSION
 124 static const uint8_t escapeSequences_2022KR[][5] = {
 125     {0x1b, 0x24, 0x29, 0x43, 0x00}
 126 };
 127
 128 static const uint8_t escapeSequences_2022CN[][5] = {
 129     {0x1b, 0x24, 0x29, 0x41, 0x00},   // GB 2312-80
 130     {0x1b, 0x24, 0x29, 0x47, 0x00},   // CNS 11643-1992 Plane 1
 131     {0x1b, 0x24, 0x2A, 0x48, 0x00},   // CNS 11643-1992 Plane 2
 132     {0x1b, 0x24, 0x29, 0x45, 0x00},   // ISO-IR-165
 133     {0x1b, 0x24, 0x2B, 0x49, 0x00},   // CNS 11643-1992 Plane 3
 134     {0x1b, 0x24, 0x2B, 0x4A, 0x00},   // CNS 11643-1992 Plane 4
 135     {0x1b, 0x24, 0x2B, 0x4B, 0x00},   // CNS 11643-1992 Plane 5
 136     {0x1b, 0x24, 0x2B, 0x4C, 0x00},   // CNS 11643-1992 Plane 6
 137     {0x1b, 0x24, 0x2B, 0x4D, 0x00},   // CNS 11643-1992 Plane 7
 138     {0x1b, 0x4e, 0x00, 0x00, 0x00},   // SS2
 139     {0x1b, 0x4f, 0x00, 0x00, 0x00},   // SS3
 140 };
 141 #endif
 142
 143 CharsetRecog_2022JP::~CharsetRecog_2022JP() {}
 144
 145 const char *CharsetRecog_2022JP::getName() const {
 146     return "ISO-2022-JP";
 147 }
 148
 149 UBool CharsetRecog_2022JP::match(InputText *textIn, CharsetMatch *results) const {
 150     int32_t confidence = match_2022(textIn->fInputBytes,
 151                                     textIn->fInputLen,
 152                                     escapeSequences_2022JP,
 153                                     UPRV_LENGTHOF(escapeSequences_2022JP));
 154     results->set(textIn, this, confidence);
 155     return (confidence > 0);
 156 }
 157
 158 #if !UCONFIG_ONLY_HTML_CONVERSION
 159 CharsetRecog_2022KR::~CharsetRecog_2022KR() {}
 160
 161 const char *CharsetRecog_2022KR::getName() const {
 162     return "ISO-2022-KR";
 163 }
 164
 165 UBool CharsetRecog_2022KR::match(InputText *textIn, CharsetMatch *results) const {
 166     int32_t confidence = match_2022(textIn->fInputBytes,
 167                                     textIn->fInputLen,
 168                                     escapeSequences_2022KR,
 169                                     UPRV_LENGTHOF(escapeSequences_2022KR));
 170     results->set(textIn, this, confidence);
 171     return (confidence > 0);
 172 }
 173
 174 CharsetRecog_2022CN::~CharsetRecog_2022CN() {}
 175
 176 const char *CharsetRecog_2022CN::getName() const {
 177     return "ISO-2022-CN";
 178 }
 179
 180 UBool CharsetRecog_2022CN::match(InputText *textIn, CharsetMatch *results) const {
 181     int32_t confidence = match_2022(textIn->fInputBytes,
 182                                     textIn->fInputLen,
 183                                     escapeSequences_2022CN,
 184                                     UPRV_LENGTHOF(escapeSequences_2022CN));
 185     results->set(textIn, this, confidence);
 186     return (confidence > 0);
 187 }
 188 #endif
 189
 190 CharsetRecog_2022::~CharsetRecog_2022() {
 191     // nothing to do
 192 }
 193
 194 U_NAMESPACE_END
 195 #endif