contrib/nvi2/common/encoding.c

   1 /*-
   2  * Copyright (c) 2011, 2012
   3  *      Zhihao Yuan.  All rights reserved.
   4  *
   5  * See the LICENSE file for redistribution information.
   6  */
   7
   8 #ifndef lint
   9 static const char sccsid[] = "$Id: encoding.c,v 1.4 2011/12/13 19:40:52 zy Exp $";
  10 #endif /* not lint */
  11
  12 #include <sys/types.h>
  13
  14 int looks_utf8(const char *, size_t);
  15 int looks_utf16(const char *, size_t);
  16 int decode_utf8(const char *);
  17 int decode_utf16(const char *, int);
  18
  19 #define F 0   /* character never appears in text */
  20 #define T 1   /* character appears in plain ASCII text */
  21 #define I 2   /* character appears in ISO-8859 text */
  22 #define X 3   /* character appears in non-ISO extended ASCII (Mac, IBM PC) */
  23
  24 static char text_chars[256] = {
  25         /*                  BEL BS HT LF    FF CR    */
  26         F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F,  /* 0x0X */
  27         /*                              ESC          */
  28         F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F,  /* 0x1X */
  29         T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,  /* 0x2X */
  30         T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,  /* 0x3X */
  31         T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,  /* 0x4X */
  32         T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,  /* 0x5X */
  33         T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,  /* 0x6X */
  34         T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F,  /* 0x7X */
  35         /*            NEL                            */
  36         X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X,  /* 0x8X */
  37         X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X,  /* 0x9X */
  38         I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I,  /* 0xaX */
  39         I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I,  /* 0xbX */
  40         I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I,  /* 0xcX */
  41         I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I,  /* 0xdX */
  42         I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I,  /* 0xeX */
  43         I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I   /* 0xfX */
  44 };
  45
  46 /*
  47  * looks_utf8 --
  48  *  Decide whether some text looks like UTF-8. Returns:
  49  *
  50  *     -1: invalid UTF-8
  51  *      0: uses odd control characters, so doesn't look like text
  52  *      1: 7-bit text
  53  *      2: definitely UTF-8 text (valid high-bit set bytes)
  54  *
  55  *  Based on RFC 3629. UTF-8 with BOM is not accepted.
  56  *
  57  * PUBLIC: int looks_utf8(const char *, size_t);
  58  */
  59 int
  60 looks_utf8(const char *ibuf, size_t nbytes)
  61 {
  62         const u_char *buf = (u_char *)ibuf;
  63         size_t i;
  64         int n;
  65         int gotone = 0, ctrl = 0;
  66
  67         for (i = 0; i < nbytes; i++) {
  68                 if ((buf[i] & 0x80) == 0) {        /* 0xxxxxxx is plain ASCII */
  69                         /*
  70                          * Even if the whole file is valid UTF-8 sequences,
  71                          * still reject it if it uses weird control characters.
  72                          */
  73
  74                         if (text_chars[buf[i]] != T)
  75                                 ctrl = 1;
  76                 } else if ((buf[i] & 0x40) == 0) { /* 10xxxxxx never 1st byte */
  77                         return -1;
  78                 } else {                           /* 11xxxxxx begins UTF-8 */
  79                         int following;
  80
  81                         if ((buf[i] & 0x20) == 0)       /* 110xxxxx */
  82                                 if (buf[i] > 0xC1)      /* C0, C1 */
  83                                         following = 1;
  84                                 else return -1;
  85                         else if ((buf[i] & 0x10) == 0)  /* 1110xxxx */
  86                                 following = 2;
  87                         else if ((buf[i] & 0x08) == 0)  /* 11110xxx */
  88                                 if (buf[i] < 0xF5)
  89                                         following = 3;
  90                                 else return -1;         /* F5, F6, F7 */
  91                         else
  92                                 return -1;              /* F8~FF */
  93
  94                         for (n = 0; n < following; n++) {
  95                                 i++;
  96                                 if (i >= nbytes)
  97                                         goto done;
  98
  99                                 if (buf[i] & 0x40)      /* 10xxxxxx */
 100                                         return -1;
 101                         }
 102
 103                         gotone = 1;
 104                 }
 105         }
 106 done:
 107         return ctrl ? 0 : (gotone ? 2 : 1);
 108 }
 109
 110 /*
 111  * looks_utf16 --
 112  *  Decide whether some text looks like UTF-16. Returns:
 113  *
 114  *      0: invalid UTF-16
 115  *      1: Little-endian UTF-16
 116  *      2: Big-endian UTF-16
 117  *
 118  * PUBLIC: int looks_utf16(const char *, size_t);
 119  */
 120 int
 121 looks_utf16(const char *ibuf, size_t nbytes)
 122 {
 123         const u_char *buf = (u_char *)ibuf;
 124         int bigend;
 125         size_t i;
 126         unsigned int c;
 127         int bom;
 128         int following = 0;
 129
 130         if (nbytes < 2)
 131                 return 0;
 132
 133         bom = buf[0] << 8 ^ buf[1];
 134         if (bom == 0xFFFE)
 135                 bigend = 0;
 136         else if (bom == 0xFEFF)
 137                 bigend = 1;
 138         else
 139                 return 0;
 140
 141         for (i = 2; i + 1 < nbytes; i += 2) {
 142                 if (bigend)
 143                         c = buf[i] << 8 ^ buf[i + 1];
 144                 else
 145                         c = buf[i] ^ buf[i + 1] << 8;
 146
 147                 if (!following)
 148                         if (c < 0xD800 || c > 0xDFFF)
 149                                 if (c < 128 && text_chars[c] != T)
 150                                         return 0;
 151                                 else
 152                                         following = 0;
 153                         else if (c > 0xDBFF)
 154                                 return 0;
 155                         else {
 156                                 following = 1;
 157                                 continue;
 158                         }
 159                 else if (c < 0xDC00 || c > 0xDFFF)
 160                         return 0;
 161         }
 162
 163         return 1 + bigend;
 164 }
 165
 166 #undef F
 167 #undef T
 168 #undef I
 169 #undef X
 170
 171 /*
 172  * decode_utf8 --
 173  *  Decode a UTF-8 character from byte string to Unicode.
 174  *  Returns -1 if the first byte is a not UTF-8 leader.
 175  *
 176  *  Based on RFC 3629, but without error detection.
 177  *
 178  * PUBLIC: int decode_utf8(const char *);
 179  */
 180 int
 181 decode_utf8(const char *ibuf)
 182 {
 183         const u_char *buf = (u_char *)ibuf;
 184         int u = -1;
 185
 186         if ((buf[0] & 0x80) == 0)
 187                 u = buf[0];
 188         else if ((buf[0] & 0x40) == 0);
 189         else {
 190                 if ((buf[0] & 0x20) == 0)
 191                         u = (buf[0] ^ 0xC0) <<  6 ^ (buf[1] ^ 0x80);
 192                 else if ((buf[0] & 0x10) == 0)
 193                         u = (buf[0] ^ 0xE0) << 12 ^ (buf[1] ^ 0x80) <<  6
 194                           ^ (buf[2] ^ 0x80);
 195                 else if (((buf[0] & 0x08) == 0))
 196                         u = (buf[0] ^ 0xF0) << 18 ^ (buf[1] ^ 0x80) << 12
 197                           ^ (buf[2] ^ 0x80) <<  6 ^ (buf[3] ^ 0x80);
 198         }
 199
 200         return u;
 201 }
 202
 203 /*
 204  * decode_utf16 --
 205  *  Decode a UTF-16 character from byte string to Unicode.
 206  *  Returns -1 if the first unsigned integer is invalid.
 207  *
 208  *  No error detection on supplementary bytes.
 209  *
 210  * PUBLIC: int decode_utf16(const char *, int);
 211  */
 212 int
 213 decode_utf16(const char* ibuf, int bigend)
 214 {
 215         const u_char *buf = (u_char *)ibuf;
 216         int u = -1;
 217         unsigned int w1, w2;
 218
 219         if (bigend)
 220                 w1 = buf[0] << 8 ^ buf[1];
 221         else
 222                 w1 = buf[0] ^ buf[1] << 8;
 223
 224         if (w1 < 0xD800 || w1 > 0xDFFF)
 225                 u = w1;
 226         else if (w1 > 0xDBFF);
 227         else {
 228                 if (bigend)
 229                         w2 = buf[2] << 8 ^ buf[3];
 230                 else
 231                         w2 = buf[2] ^ buf[3] << 8;
 232                 u = ((w1 ^ 0xD800) << 10 ^ (w2 ^ 0xDC00)) + 0x10000;
 233         }
 234
 235         return u;
 236 }