diff options
Diffstat (limited to 'src/str/ft_strlen.c')
| -rw-r--r-- | src/str/ft_strlen.c | 54 |
1 files changed, 19 insertions, 35 deletions
diff --git a/src/str/ft_strlen.c b/src/str/ft_strlen.c index 72405c4..999763e 100644 --- a/src/str/ft_strlen.c +++ b/src/str/ft_strlen.c @@ -6,7 +6,7 @@ /* By: cacharle <marvin@42.fr> +#+ +:+ +#+ */ /* +#+#+#+#+#+ +#+ */ /* Created: 2019/10/07 10:32:48 by cacharle #+# #+# */ -/* Updated: 2020/01/17 11:13:43 by cacharle ### ########.fr */ +/* Updated: 2020/04/01 21:45:38 by charles ### ########.fr */ /* */ /* ************************************************************************** */ @@ -22,18 +22,22 @@ ** ** 0x7F -> 0b 0111 1111 ** -** null_high = lw & 0x7F7F7F7F // will set the high bit of each byte to 0 -** overflow = null_high + 0x7F7F7F7F // addition will overflow the high bit is one of the other bits was 1. -** -** oring = overflow | lw // the high bit of a byte is set iff any bit in the byte was set -** ones = oring | 0x7F7F7F7F // the high bits and ones everywhere else -** has_no_zero_byte = ~ones // the ones become zeros, if no high bit was set, there was no zero +** null_high = lw & 0x7F7F7F7F // will set the high bit of each byte to 0 +** overflow = null_high + 0x7F7F7F7F // addition will overflow the high bit +** is one of the other bits was 1. ** +** oring = overflow | lw // the high bit of a byte is set +** iff any bit in the byte was set +** ones = oring | 0x7F7F7F7F // the high bits and ones everywhere else +** has_no_zero_byte = ~ones // the ones become zeros, if no high bit +** was set, there was no zero ** ** (lw - 0x01010101) & ~lw & 0x80808080 ** -** overflow = lw - 0x01010101 // overflow the high bit if one was 0 or > 0x80 (0b 1000 0000) 0 || >0x80 -** no_high_bit = ~lw & 0x80808080 // high bit set if the high bit was 0 (i.e < 0x80) 0 || <0x80 +** overflow = lw - 0x01010101 // overflow the high bit if one was +** 0 or > 0x80 (0b 1000 0000) 0 || >0x80 +** no_high_bit = ~lw & 0x80808080 // high bit set if the high bit was +** 0 (i.e < 0x80) 0 || <0x80 ** has_zero = overflow & no_high_bit // (0 || >0x80) && (0 || <0x80) -> 0 && 0 ** ** @@ -52,38 +56,18 @@ size_t ft_strlen(const char *s) { uint64_t *ptr; const char *cpy; - uint64_t lw; + const char *found; cpy = s; while (((uint64_t)cpy & 0b111) != 0) - { - if (*cpy == 0) - return (cpy - s); - cpy++; - } + if (*cpy++ == '\0') + return (cpy - s - 1); ptr = (uint64_t*)cpy; while (TRUE) - { - lw = *ptr++; - if (((lw - LOMAGIC) & HIMAGIC) != 0) + if (((*ptr++ - LOMAGIC) & HIMAGIC) != 0) { cpy = (const char*)(ptr - 1); - if (cpy[0] == '\0') - return (cpy - s); - if (cpy[1] == '\0') - return (cpy - s + 1); - if (cpy[2] == '\0') - return (cpy - s + 2); - if (cpy[3] == '\0') - return (cpy - s + 3); - if (cpy[4] == '\0') - return (cpy - s + 4); - if (cpy[5] == '\0') - return (cpy - s + 5); - if (cpy[6] == '\0') - return (cpy - s + 6); - if (cpy[7] == '\0') - return (cpy - s + 7); + if ((found = ft_memchr(cpy, '\0', sizeof(uint64_t))) != NULL) + return (found - s); } - } } |