1/*
2 **********************************************************************
3 *   Copyright (C) 2005-2012, 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#include "csmatch.h"
16
17U_NAMESPACE_BEGIN
18
19#define ARRAY_SIZE(array) (sizeof array / sizeof array[0])
20
21/**
22 * Matching function shared among the 2022 detectors JP, CN and KR
23 * Counts up the number of legal and unrecognized escape sequences in
24 * the sample of text, and computes a score based on the total number &
25 * the proportion that fit the encoding.
26 *
27 *
28 * @param text the byte buffer containing text to analyse
29 * @param textLen  the size of the text in the byte.
30 * @param escapeSequences the byte escape sequences to test for.
31 * @return match quality, in the range of 0-100.
32 */
33int32_t CharsetRecog_2022::match_2022(const uint8_t *text, int32_t textLen, const uint8_t escapeSequences[][5], int32_t escapeSequences_length) const
34{
35    int32_t i, j;
36    int32_t escN;
37    int32_t hits   = 0;
38    int32_t misses = 0;
39    int32_t shifts = 0;
40    int32_t quality;
41
42    i = 0;
43    while(i < textLen) {
44        if(text[i] == 0x1B) {
45            escN = 0;
46            while(escN < escapeSequences_length) {
47                const uint8_t *seq = escapeSequences[escN];
48                int32_t seq_length = (int32_t)uprv_strlen((const char *) seq);
49
50                if (textLen-i >= seq_length) {
51                    j = 1;
52                    while(j < seq_length) {
53                        if(seq[j] != text[i+j]) {
54                            goto checkEscapes;
55                        }
56
57                        j += 1;
58                    }
59
60                    hits += 1;
61                    i += seq_length-1;
62                    goto scanInput;
63                }
64                // else we ran out of string to compare this time.
65checkEscapes:
66                escN += 1;
67            }
68
69            misses += 1;
70        }
71
72        if( text[i]== 0x0e || text[i] == 0x0f){
73            shifts += 1;
74        }
75
76scanInput:
77        i += 1;
78    }
79
80    if (hits == 0) {
81        return 0;
82    }
83
84    //
85    // Initial quality is based on relative proportion of recongized vs.
86    //   unrecognized escape sequences.
87    //   All good:  quality = 100;
88    //   half or less good: quality = 0;
89    //   linear inbetween.
90    quality = (100*hits - 100*misses) / (hits + misses);
91
92    // Back off quality if there were too few escape sequences seen.
93    //   Include shifts in this computation, so that KR does not get penalized
94    //   for having only a single Escape sequence, but many shifts.
95    if (hits+shifts < 5) {
96        quality -= (5-(hits+shifts))*10;
97    }
98
99    if (quality < 0) {
100        quality = 0;
101    }
102
103    return quality;
104}
105
106
107static const uint8_t escapeSequences_2022JP[][5] = {
108    {0x1b, 0x24, 0x28, 0x43, 0x00},   // KS X 1001:1992
109    {0x1b, 0x24, 0x28, 0x44, 0x00},   // JIS X 212-1990
110    {0x1b, 0x24, 0x40, 0x00, 0x00},   // JIS C 6226-1978
111    {0x1b, 0x24, 0x41, 0x00, 0x00},   // GB 2312-80
112    {0x1b, 0x24, 0x42, 0x00, 0x00},   // JIS X 208-1983
113    {0x1b, 0x26, 0x40, 0x00, 0x00},   // JIS X 208 1990, 1997
114    {0x1b, 0x28, 0x42, 0x00, 0x00},   // ASCII
115    {0x1b, 0x28, 0x48, 0x00, 0x00},   // JIS-Roman
116    {0x1b, 0x28, 0x49, 0x00, 0x00},   // Half-width katakana
117    {0x1b, 0x28, 0x4a, 0x00, 0x00},   // JIS-Roman
118    {0x1b, 0x2e, 0x41, 0x00, 0x00},   // ISO 8859-1
119    {0x1b, 0x2e, 0x46, 0x00, 0x00}    // ISO 8859-7
120};
121
122static const uint8_t escapeSequences_2022KR[][5] = {
123    {0x1b, 0x24, 0x29, 0x43, 0x00}
124};
125
126static const uint8_t escapeSequences_2022CN[][5] = {
127    {0x1b, 0x24, 0x29, 0x41, 0x00},   // GB 2312-80
128    {0x1b, 0x24, 0x29, 0x47, 0x00},   // CNS 11643-1992 Plane 1
129    {0x1b, 0x24, 0x2A, 0x48, 0x00},   // CNS 11643-1992 Plane 2
130    {0x1b, 0x24, 0x29, 0x45, 0x00},   // ISO-IR-165
131    {0x1b, 0x24, 0x2B, 0x49, 0x00},   // CNS 11643-1992 Plane 3
132    {0x1b, 0x24, 0x2B, 0x4A, 0x00},   // CNS 11643-1992 Plane 4
133    {0x1b, 0x24, 0x2B, 0x4B, 0x00},   // CNS 11643-1992 Plane 5
134    {0x1b, 0x24, 0x2B, 0x4C, 0x00},   // CNS 11643-1992 Plane 6
135    {0x1b, 0x24, 0x2B, 0x4D, 0x00},   // CNS 11643-1992 Plane 7
136    {0x1b, 0x4e, 0x00, 0x00, 0x00},   // SS2
137    {0x1b, 0x4f, 0x00, 0x00, 0x00},   // SS3
138};
139
140CharsetRecog_2022JP::~CharsetRecog_2022JP() {}
141
142const char *CharsetRecog_2022JP::getName() const {
143    return "ISO-2022-JP";
144}
145
146UBool CharsetRecog_2022JP::match(InputText *textIn, CharsetMatch *results) const {
147    int32_t confidence = match_2022(textIn->fInputBytes,
148                                    textIn->fInputLen,
149                                    escapeSequences_2022JP,
150                                    ARRAY_SIZE(escapeSequences_2022JP));
151    results->set(textIn, this, confidence);
152    return (confidence > 0);
153}
154
155CharsetRecog_2022KR::~CharsetRecog_2022KR() {}
156
157const char *CharsetRecog_2022KR::getName() const {
158    return "ISO-2022-KR";
159}
160
161UBool CharsetRecog_2022KR::match(InputText *textIn, CharsetMatch *results) const {
162    int32_t confidence = match_2022(textIn->fInputBytes,
163                                    textIn->fInputLen,
164                                    escapeSequences_2022KR,
165                                    ARRAY_SIZE(escapeSequences_2022KR));
166    results->set(textIn, this, confidence);
167    return (confidence > 0);
168}
169
170CharsetRecog_2022CN::~CharsetRecog_2022CN() {}
171
172const char *CharsetRecog_2022CN::getName() const {
173    return "ISO-2022-CN";
174}
175
176UBool CharsetRecog_2022CN::match(InputText *textIn, CharsetMatch *results) const {
177    int32_t confidence = match_2022(textIn->fInputBytes,
178                                    textIn->fInputLen,
179                                    escapeSequences_2022CN,
180                                    ARRAY_SIZE(escapeSequences_2022CN));
181    results->set(textIn, this, confidence);
182    return (confidence > 0);
183}
184
185CharsetRecog_2022::~CharsetRecog_2022() {
186    // nothing to do
187}
188
189U_NAMESPACE_END
190#endif
191