1/*
2 **********************************************************************
3 *   Copyright (C) 2005-2009, 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
16U_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 */
32int32_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                const uint8_t *seq = escapeSequences[escN];
47                int32_t seq_length = (int32_t)uprv_strlen((const char *) seq);
48
49                if (textLen-i >= seq_length) {
50                    j = 1;
51                    while(j < seq_length) {
52                        if(seq[j] != text[i+j]) {
53                            goto checkEscapes;
54                        }
55
56                        j += 1;
57                    }
58
59                    hits += 1;
60                    i += seq_length-1;
61                    goto scanInput;
62                }
63                // else we ran out of string to compare this time.
64checkEscapes:
65                escN += 1;
66            }
67
68            misses += 1;
69        }
70
71        if( text[i]== 0x0e || text[i] == 0x0f){
72            shifts += 1;
73        }
74
75scanInput:
76        i += 1;
77    }
78
79    if (hits == 0) {
80        return 0;
81    }
82
83    //
84    // Initial quality is based on relative proportion of recongized vs.
85    //   unrecognized escape sequences.
86    //   All good:  quality = 100;
87    //   half or less good: quality = 0;
88    //   linear inbetween.
89    quality = (100*hits - 100*misses) / (hits + misses);
90
91    // Back off quality if there were too few escape sequences seen.
92    //   Include shifts in this computation, so that KR does not get penalized
93    //   for having only a single Escape sequence, but many shifts.
94    if (hits+shifts < 5) {
95        quality -= (5-(hits+shifts))*10;
96    }
97
98    if (quality < 0) {
99        quality = 0;
100    }
101
102    return quality;
103}
104
105
106static const uint8_t escapeSequences_2022JP[][5] = {
107    {0x1b, 0x24, 0x28, 0x43, 0x00},   // KS X 1001:1992
108    {0x1b, 0x24, 0x28, 0x44, 0x00},   // JIS X 212-1990
109    {0x1b, 0x24, 0x40, 0x00, 0x00},   // JIS C 6226-1978
110    {0x1b, 0x24, 0x41, 0x00, 0x00},   // GB 2312-80
111    {0x1b, 0x24, 0x42, 0x00, 0x00},   // JIS X 208-1983
112    {0x1b, 0x26, 0x40, 0x00, 0x00},   // JIS X 208 1990, 1997
113    {0x1b, 0x28, 0x42, 0x00, 0x00},   // ASCII
114    {0x1b, 0x28, 0x48, 0x00, 0x00},   // JIS-Roman
115    {0x1b, 0x28, 0x49, 0x00, 0x00},   // Half-width katakana
116    {0x1b, 0x28, 0x4a, 0x00, 0x00},   // JIS-Roman
117    {0x1b, 0x2e, 0x41, 0x00, 0x00},   // ISO 8859-1
118    {0x1b, 0x2e, 0x46, 0x00, 0x00}    // ISO 8859-7
119};
120
121static const uint8_t escapeSequences_2022KR[][5] = {
122    {0x1b, 0x24, 0x29, 0x43, 0x00}
123};
124
125static const uint8_t escapeSequences_2022CN[][5] = {
126    {0x1b, 0x24, 0x29, 0x41, 0x00},   // GB 2312-80
127    {0x1b, 0x24, 0x29, 0x47, 0x00},   // CNS 11643-1992 Plane 1
128    {0x1b, 0x24, 0x2A, 0x48, 0x00},   // CNS 11643-1992 Plane 2
129    {0x1b, 0x24, 0x29, 0x45, 0x00},   // ISO-IR-165
130    {0x1b, 0x24, 0x2B, 0x49, 0x00},   // CNS 11643-1992 Plane 3
131    {0x1b, 0x24, 0x2B, 0x4A, 0x00},   // CNS 11643-1992 Plane 4
132    {0x1b, 0x24, 0x2B, 0x4B, 0x00},   // CNS 11643-1992 Plane 5
133    {0x1b, 0x24, 0x2B, 0x4C, 0x00},   // CNS 11643-1992 Plane 6
134    {0x1b, 0x24, 0x2B, 0x4D, 0x00},   // CNS 11643-1992 Plane 7
135    {0x1b, 0x4e, 0x00, 0x00, 0x00},   // SS2
136    {0x1b, 0x4f, 0x00, 0x00, 0x00},   // SS3
137};
138
139const char *CharsetRecog_2022JP::getName() const
140{
141    return "ISO-2022-JP";
142}
143
144int32_t CharsetRecog_2022JP::match(InputText *textIn)
145{
146    return match_2022(textIn->fInputBytes, textIn->fInputLen, escapeSequences_2022JP, ARRAY_SIZE(escapeSequences_2022JP));
147}
148
149const char *CharsetRecog_2022KR::getName() const
150{
151    return "ISO-2022-KR";
152}
153
154int32_t CharsetRecog_2022KR::match(InputText *textIn)
155{
156    return match_2022(textIn->fInputBytes, textIn->fInputLen, escapeSequences_2022KR, ARRAY_SIZE(escapeSequences_2022KR));
157}
158
159const char *CharsetRecog_2022CN::getName() const
160{
161    return "ISO-2022-CN";
162}
163
164int32_t CharsetRecog_2022CN::match(InputText *textIn)
165{
166    return match_2022(textIn->fInputBytes, textIn->fInputLen, escapeSequences_2022CN, ARRAY_SIZE(escapeSequences_2022CN));
167}
168
169CharsetRecog_2022::~CharsetRecog_2022()
170{
171    // nothing to do
172}
173
174U_NAMESPACE_END
175#endif
176