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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  */
match_2022(const uint8_t * text,int32_t textLen,const uint8_t escapeSequences[][5],int32_t escapeSequences_length) const34 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 
~CharsetRecog_2022JP()143 CharsetRecog_2022JP::~CharsetRecog_2022JP() {}
144 
getName() const145 const char *CharsetRecog_2022JP::getName() const {
146     return "ISO-2022-JP";
147 }
148 
match(InputText * textIn,CharsetMatch * results) const149 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
~CharsetRecog_2022KR()159 CharsetRecog_2022KR::~CharsetRecog_2022KR() {}
160 
getName() const161 const char *CharsetRecog_2022KR::getName() const {
162     return "ISO-2022-KR";
163 }
164 
match(InputText * textIn,CharsetMatch * results) const165 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 
~CharsetRecog_2022CN()174 CharsetRecog_2022CN::~CharsetRecog_2022CN() {}
175 
getName() const176 const char *CharsetRecog_2022CN::getName() const {
177     return "ISO-2022-CN";
178 }
179 
match(InputText * textIn,CharsetMatch * results) const180 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 
~CharsetRecog_2022()190 CharsetRecog_2022::~CharsetRecog_2022() {
191     // nothing to do
192 }
193 
194 U_NAMESPACE_END
195 #endif
196