1// Copyright (C) 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
20U_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 */
34int32_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.
66checkEscapes:
67                escN += 1;
68            }
69
70            misses += 1;
71        }
72
73        if( text[i]== 0x0e || text[i] == 0x0f){
74            shifts += 1;
75        }
76
77scanInput:
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
108static 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
124static const uint8_t escapeSequences_2022KR[][5] = {
125    {0x1b, 0x24, 0x29, 0x43, 0x00}
126};
127
128static 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
143CharsetRecog_2022JP::~CharsetRecog_2022JP() {}
144
145const char *CharsetRecog_2022JP::getName() const {
146    return "ISO-2022-JP";
147}
148
149UBool 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
159CharsetRecog_2022KR::~CharsetRecog_2022KR() {}
160
161const char *CharsetRecog_2022KR::getName() const {
162    return "ISO-2022-KR";
163}
164
165UBool 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
174CharsetRecog_2022CN::~CharsetRecog_2022CN() {}
175
176const char *CharsetRecog_2022CN::getName() const {
177    return "ISO-2022-CN";
178}
179
180UBool 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
190CharsetRecog_2022::~CharsetRecog_2022() {
191    // nothing to do
192}
193
194U_NAMESPACE_END
195#endif
196