diff options
Diffstat (limited to 'src/util.c')
| -rw-r--r-- | src/util.c | 75 |
1 files changed, 75 insertions, 0 deletions
@@ -152,3 +152,78 @@ void msleep(int ms) nanosleep(&ts, NULL); } +/** + * Check whether a NUL-terminated string is encoded in UTF-8 + * + * @param string The string + * @param allow_modified_nul Whether Modified UTF-8 is allowed, which allows a two-byte encoding for NUL + * @return Zero if good, -1 on encoding error + */ +int verify_utf8(const char* string, int allow_modified_nul) +{ + static long BYTES_TO_MIN_BITS[] = {0, 0, 8, 12, 17, 22, 37}; + static long BYTES_TO_MAX_BITS[] = {0, 7, 11, 16, 21, 26, 31}; + long bytes = 0, read_bytes = 0, bits = 0, c, character; + + /* min bits max bits + 0....... 0 7 + 110..... 10...... 8 11 + 1110.... 10...... 10...... 12 16 + 11110... 10...... 10...... 10...... 17 21 + 111110.. 10...... 10...... 10...... 10...... 22 26 + 1111110. 10...... 10...... 10...... 10...... 10...... 27 31 + */ + + while ((c = (long)(*string++))) + if (read_bytes == 0) + { + /* First byte of the character. */ + + if ((c & 0x80) == 0x00) + /* Single-byte character. */ + continue; + + if ((c & 0xC0) == 0x80) + /* Single-byte character marked as multibyte, or + a non-first byte in a multibyte character. */ + return -1; + + /* Multibyte character. */ + while ((c & 0x80)) + bytes++, c <<= 1; + read_bytes = 1; + character = c & 0x7F; + if (bytes > 6) + /* 31-bit characters can be encoded with 6-bytes, + and UTF-8 does not cover higher code points. */ + return -1; + } + else + { + /* Not first byte of the character. */ + + if ((c & 0xC0) != 0x80) + /* Beginning of new character before a + multibyte character has ended. */ + return -1; + + character = (character << 6) | (c & 0x7F); + + if (++read_bytes < bytes) + /* Not at last byte yet. */ + continue; + + /* Check that the character is not unnecessarily long. */ + while (character) + character >>= 1, bits++; + bits = ((bits == 0) && (bytes == 2) && allow_modified_nul) ? 8 : bits; + if ((bits < BYTES_TO_MIN_BITS[bytes]) || (BYTES_TO_MAX_BITS[bytes] < bits)) + return -1; + + read_bytes = bytes = bits = 0; + } + + /* Make sure we did not stop at the middle of a multibyte character. */ + return read_bytes == 0 ? 0 : -1; +} + |