1 /*
2 **********************************************************************
3 * Copyright (C) 2005-2006, International Business Machines
4 * Corporation and others. All Rights Reserved.
5 **********************************************************************
6 */
7
8 #include "unicode/utypes.h"
9
10 #if !UCONFIG_NO_CONVERSION
11
12 #include "cstring.h"
13
14 #include "csr2022.h"
15
16 U_NAMESPACE_BEGIN
17
18 #define ARRAY_SIZE(array) (sizeof array / sizeof array[0])
19
20 /**
21 * Matching function shared among the 2022 detectors JP, CN and KR
22 * Counts up the number of legal an unrecognized escape sequences in
23 * the sample of text, and computes a score based on the total number &
24 * the proportion that fit the encoding.
25 *
26 *
27 * @param text the byte buffer containing text to analyse
28 * @param textLen the size of the text in the byte.
29 * @param escapeSequences the byte escape sequences to test for.
30 * @return match quality, in the range of 0-100.
31 */
match_2022(const uint8_t * text,int32_t textLen,const uint8_t escapeSequences[][5],int32_t escapeSequences_length)32 int32_t CharsetRecog_2022::match_2022(const uint8_t *text, int32_t textLen, const uint8_t escapeSequences[][5], int32_t escapeSequences_length)
33 {
34 int32_t i, j;
35 int32_t escN;
36 int32_t hits = 0;
37 int32_t misses = 0;
38 int32_t shifts = 0;
39 int32_t quality;
40
41 i = 0;
42 while(i < textLen) {
43 if(text[i] == 0x1B) {
44 escN = 0;
45 while(escN < escapeSequences_length) {
46 int32_t seq_length = uprv_strlen((const char *) escapeSequences[escN]);
47 const uint8_t *seq = escapeSequences[escN];
48
49 j = 1;
50 while(j < seq_length) {
51 if(seq[j] != text[i+j]) {
52 goto checkEscapes;
53 }
54
55 j += 1;
56 }
57
58 hits += 1;
59 i += seq_length-1;
60 goto scanInput;
61 checkEscapes:
62 escN += 1;
63 }
64
65 misses += 1;
66 }
67
68 if( text[i]== 0x0e || text[i] == 0x0f){
69 shifts += 1;
70 }
71
72 scanInput:
73 i += 1;
74 }
75
76 if (hits == 0) {
77 return 0;
78 }
79
80 //
81 // Initial quality is based on relative proportion of recongized vs.
82 // unrecognized escape sequences.
83 // All good: quality = 100;
84 // half or less good: quality = 0;
85 // linear inbetween.
86 quality = (100*hits - 100*misses) / (hits + misses);
87
88 // Back off quality if there were too few escape sequences seen.
89 // Include shifts in this computation, so that KR does not get penalized
90 // for having only a single Escape sequence, but many shifts.
91 if (hits+shifts < 5) {
92 quality -= (5-(hits+shifts))*10;
93 }
94
95 if (quality < 0) {
96 quality = 0;
97 }
98
99 return quality;
100 }
101
102
103 static const uint8_t escapeSequences_2022JP[][5] = {
104 {0x1b, 0x24, 0x28, 0x43, 0x00}, // KS X 1001:1992
105 {0x1b, 0x24, 0x28, 0x44, 0x00}, // JIS X 212-1990
106 {0x1b, 0x24, 0x40, 0x00, 0x00}, // JIS C 6226-1978
107 {0x1b, 0x24, 0x41, 0x00, 0x00}, // GB 2312-80
108 {0x1b, 0x24, 0x42, 0x00, 0x00}, // JIS X 208-1983
109 {0x1b, 0x26, 0x40, 0x00, 0x00}, // JIS X 208 1990, 1997
110 {0x1b, 0x28, 0x42, 0x00, 0x00}, // ASCII
111 {0x1b, 0x28, 0x48, 0x00, 0x00}, // JIS-Roman
112 {0x1b, 0x28, 0x49, 0x00, 0x00}, // Half-width katakana
113 {0x1b, 0x28, 0x4a, 0x00, 0x00}, // JIS-Roman
114 {0x1b, 0x2e, 0x41, 0x00, 0x00}, // ISO 8859-1
115 {0x1b, 0x2e, 0x46, 0x00, 0x00} // ISO 8859-7
116 };
117
118 static const uint8_t escapeSequences_2022KR[][5] = {
119 {0x1b, 0x24, 0x29, 0x43, 0x00}
120 };
121
122 static const uint8_t escapeSequences_2022CN[][5] = {
123 {0x1b, 0x24, 0x29, 0x41, 0x00}, // GB 2312-80
124 {0x1b, 0x24, 0x29, 0x47, 0x00}, // CNS 11643-1992 Plane 1
125 {0x1b, 0x24, 0x2A, 0x48, 0x00}, // CNS 11643-1992 Plane 2
126 {0x1b, 0x24, 0x29, 0x45, 0x00}, // ISO-IR-165
127 {0x1b, 0x24, 0x2B, 0x49, 0x00}, // CNS 11643-1992 Plane 3
128 {0x1b, 0x24, 0x2B, 0x4A, 0x00}, // CNS 11643-1992 Plane 4
129 {0x1b, 0x24, 0x2B, 0x4B, 0x00}, // CNS 11643-1992 Plane 5
130 {0x1b, 0x24, 0x2B, 0x4C, 0x00}, // CNS 11643-1992 Plane 6
131 {0x1b, 0x24, 0x2B, 0x4D, 0x00}, // CNS 11643-1992 Plane 7
132 {0x1b, 0x4e, 0x00, 0x00, 0x00}, // SS2
133 {0x1b, 0x4f, 0x00, 0x00, 0x00}, // SS3
134 };
135
getName() const136 const char *CharsetRecog_2022JP::getName() const
137 {
138 return "ISO-2022-JP";
139 }
140
match(InputText * textIn)141 int32_t CharsetRecog_2022JP::match(InputText *textIn)
142 {
143 return match_2022(textIn->fInputBytes, textIn->fInputLen, escapeSequences_2022JP, ARRAY_SIZE(escapeSequences_2022JP));
144 }
145
getName() const146 const char *CharsetRecog_2022KR::getName() const
147 {
148 return "ISO-2022-KR";
149 }
150
match(InputText * textIn)151 int32_t CharsetRecog_2022KR::match(InputText *textIn)
152 {
153 return match_2022(textIn->fInputBytes, textIn->fInputLen, escapeSequences_2022KR, ARRAY_SIZE(escapeSequences_2022KR));
154 }
155
getName() const156 const char *CharsetRecog_2022CN::getName() const
157 {
158 return "ISO-2022-CN";
159 }
160
match(InputText * textIn)161 int32_t CharsetRecog_2022CN::match(InputText *textIn)
162 {
163 return match_2022(textIn->fInputBytes, textIn->fInputLen, escapeSequences_2022CN, ARRAY_SIZE(escapeSequences_2022CN));
164 }
165
~CharsetRecog_2022()166 CharsetRecog_2022::~CharsetRecog_2022()
167 {
168 // nothing to do
169 }
170
171 U_NAMESPACE_END
172 #endif
173