cosmopolitan/libc/str/wcslen.c
Justine Tunney 2ab9e9f7fd
Make improvements
- Introduce portable sched_getcpu() api
- Support GCC's __target_clones__ feature
- Make fma() go faster on x86 in default mode
- Remove some asan checks from core libraries
- WinMain() now ensures $HOME and $USER are defined
2024-02-12 10:23:00 -08:00

47 lines
2.5 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/dce.h"
#include "libc/str/str.h"
typedef wchar_t xmm_t __attribute__((__vector_size__(16), __aligned__(16)));
/**
* Returns length of NUL-terminated wide string.
*
* @param s is non-null NUL-terminated wide string pointer
* @return number of wide characters (excluding NUL)
* @asyncsignalsafe
*/
__vex size_t wcslen(const wchar_t *s) {
#if defined(__x86_64__) && !defined(__chibicc__)
size_t n;
xmm_t z = {0};
unsigned m, k = (uintptr_t)s & 15;
const xmm_t *p = (const xmm_t *)((uintptr_t)s & -16);
m = __builtin_ia32_pmovmskb128(*p == z) >> k << k;
while (!m) m = __builtin_ia32_pmovmskb128(*++p == z);
n = (const wchar_t *)p + (__builtin_ctzl(m) >> 2) - s;
return n;
#else
size_t n = 0;
while (*s++) ++n;
return n;
#endif
}