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Changeset 568693b in mainline


Ignore:
Timestamp:
2012-08-17T10:24:21Z (9 years ago)
Author:
Martin Sucha <sucha14@…>
Branches:
lfn, master
Children:
20dccf3
Parents:
7d27f422
Message:

Add reverse variant of str_decode.

Location:
uspace/lib/c
Files:
2 edited

Legend:

Unmodified
Added
Removed
  • uspace/lib/c/generic/str.c

    r7d27f422 r568693b  
    134134       
    135135        return ch;
     136}
     137
     138/** Decode a single character from a string to the left.
     139 *
     140 * Decode a single character from a string of size @a size. Decoding starts
     141 * at @a offset and this offset is moved to the beginning of the previous
     142 * character. In case of decoding error, offset generally decreases at least
     143 * by one. However, offset is never moved before 0.
     144 *
     145 * @param str    String (not necessarily NULL-terminated).
     146 * @param offset Byte offset in string where to start decoding.
     147 * @param size   Size of the string (in bytes).
     148 *
     149 * @return Value of decoded character, U_SPECIAL on decoding error or
     150 *         NULL if attempt to decode beyond @a start of str.
     151 *
     152 */
     153wchar_t str_decode_reverse(const char *str, size_t *offset, size_t size)
     154{
     155        if (*offset == 0)
     156                return 0;
     157       
     158        size_t processed = 0;
     159        /* Continue while continuation bytes found */
     160        while (*offset > 0 && processed < 4) {
     161                uint8_t b = (uint8_t) str[--(*offset)];
     162               
     163                if (processed == 0 && (b & 0x80) == 0) {
     164                        /* 0xxxxxxx (Plain ASCII) */
     165                        return b & 0x7f;
     166                }
     167                else if ((b & 0xe0) == 0xc0 || (b & 0xf0) == 0xe0 ||
     168                    (b & 0xf8) == 0xf0) {
     169                        /* Start byte */
     170                        size_t start_offset = *offset;
     171                        return str_decode(str, &start_offset, size);
     172                }
     173                else if ((b & 0xc0) != 0x80) {
     174                        /* Not a continuation byte */
     175                        return U_SPECIAL;
     176                }
     177                processed++;
     178        }
     179        /* Too many continuation bytes */
     180        return U_SPECIAL;
    136181}
    137182
  • uspace/lib/c/include/str.h

    r7d27f422 r568693b  
    5656
    5757extern wchar_t str_decode(const char *str, size_t *offset, size_t sz);
     58extern wchar_t str_decode_reverse(const char *str, size_t *offset, size_t sz);
    5859extern int chr_encode(const wchar_t ch, char *str, size_t *offset, size_t sz);
    5960
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