include/linux/utf.h

   1 #ifndef _LINUX_UTF_H
   2 #define _LINUX_UTF_H
   3
   4 #include <asm/unaligned.h>
   5
   6 static inline int utf8_to_utf16le(const char *s, __le16 *cp, unsigned len)
   7 {
   8         int     count = 0;
   9         u8      c;
  10         u16     uchar;
  11
  12         /*
  13          * this insists on correct encodings, though not minimal ones.
  14          * BUT it currently rejects legit 4-byte UTF-8 code points,
  15          * which need surrogate pairs.  (Unicode 3.1 can use them.)
  16          */
  17         while (len != 0 && (c = (u8) *s++) != 0) {
  18                 if ((c & 0x80)) {
  19                         /*
  20                          * 2-byte sequence:
  21                          * 00000yyyyyxxxxxx = 110yyyyy 10xxxxxx
  22                          */
  23                         if ((c & 0xe0) == 0xc0) {
  24                                 uchar = (c & 0x1f) << 6;
  25
  26                                 c = (u8) *s++;
  27                                 if ((c & 0xc0) != 0x80)
  28                                         goto fail;
  29                                 c &= 0x3f;
  30                                 uchar |= c;
  31
  32                         /*
  33                          * 3-byte sequence (most CJKV characters):
  34                          * zzzzyyyyyyxxxxxx = 1110zzzz 10yyyyyy 10xxxxxx
  35                          */
  36                         } else if ((c & 0xf0) == 0xe0) {
  37                                 uchar = (c & 0x0f) << 12;
  38
  39                                 c = (u8) *s++;
  40                                 if ((c & 0xc0) != 0x80)
  41                                         goto fail;
  42                                 c &= 0x3f;
  43                                 uchar |= c << 6;
  44
  45                                 c = (u8) *s++;
  46                                 if ((c & 0xc0) != 0x80)
  47                                         goto fail;
  48                                 c &= 0x3f;
  49                                 uchar |= c;
  50
  51                                 /* no bogus surrogates */
  52                                 if (0xd800 <= uchar && uchar <= 0xdfff)
  53                                         goto fail;
  54
  55                         /*
  56                          * 4-byte sequence (surrogate pairs, currently rare):
  57                          * 11101110wwwwzzzzyy + 110111yyyyxxxxxx
  58                          *     = 11110uuu 10uuzzzz 10yyyyyy 10xxxxxx
  59                          * (uuuuu = wwww + 1)
  60                          * FIXME accept the surrogate code points (only)
  61                          */
  62                         } else
  63                                 goto fail;
  64                 } else
  65                         uchar = c;
  66                 put_unaligned_le16(uchar, cp++);
  67                 count++;
  68                 len--;
  69         }
  70         return count;
  71 fail:
  72         return -1;
  73 }
  74
  75 #endif /* _LINUX_UTF_H */