File Manager

003 File Manager

Current Path: /usr/src/sys/libkern

📁 ..
📄 arc4random.c(6.91 KB)
📄 arc4random_uniform.c(1.78 KB)
📁 arm
📁 arm64
📄 ashldi3.c(2.43 KB)
📄 ashrdi3.c(2.56 KB)
📄 asprintf.c(2.17 KB)
📄 bcd.c(1.67 KB)
📄 bcmp.c(4.2 KB)
📄 bcopy.c(4.13 KB)
📄 bsearch.c(3.07 KB)
📄 cmpdi2.c(2.18 KB)
📄 divdi3.c(2.2 KB)
📄 explicit_bzero.c(512 B)
📄 ffs.c(1.84 KB)
📄 ffsl.c(1.85 KB)
📄 ffsll.c(1.82 KB)
📄 fls.c(1.84 KB)
📄 flsl.c(1.84 KB)
📄 flsll.c(1.85 KB)
📄 fnmatch.c(5.89 KB)
📄 gsb_crc32.c(42.96 KB)
📄 iconv.c(13.11 KB)
📄 iconv_converter_if.m(2.11 KB)
📄 iconv_ucs.c(12.47 KB)
📄 iconv_xlat.c(3.39 KB)
📄 iconv_xlat16.c(8.47 KB)
📄 inet_aton.c(3.41 KB)
📄 inet_ntoa.c(1.8 KB)
📄 inet_ntop.c(4.94 KB)
📄 inet_pton.c(5.21 KB)
📄 jenkins_hash.c(16.09 KB)
📄 lshrdi3.c(2.24 KB)
📄 mcount.c(8.52 KB)
📄 memcchr.c(3.27 KB)
📄 memchr.c(1.99 KB)
📄 memcmp.c(2 KB)
📄 memmem.c(2.39 KB)
📄 memset.c(1.61 KB)
📄 moddi3.c(2.22 KB)
📄 murmur3_32.c(3.4 KB)
📄 qdivrem.c(7.47 KB)
📄 qsort.c(5.95 KB)
📄 qsort_r.c(156 B)
📄 quad.h(4.16 KB)
📄 random.c(1.92 KB)
📄 scanc.c(1.93 KB)
📄 strcasecmp.c(2.52 KB)
📄 strcasestr.c(2.4 KB)
📄 strcat.c(1.83 KB)
📄 strchr.c(1.88 KB)
📄 strchrnul.c(1.57 KB)
📄 strcmp.c(1.96 KB)
📄 strcpy.c(1.82 KB)
📄 strcspn.c(2.36 KB)
📄 strdup.c(2.15 KB)
📄 strlcat.c(2.56 KB)
📄 strlcpy.c(1.64 KB)
📄 strlen.c(3.77 KB)
📄 strncat.c(2.23 KB)
📄 strncmp.c(1.92 KB)
📄 strncpy.c(2.15 KB)
📄 strndup.c(1.98 KB)
📄 strnlen.c(1.61 KB)
📄 strrchr.c(1.89 KB)
📄 strsep.c(2.63 KB)
📄 strspn.c(2.32 KB)
📄 strstr.c(2.11 KB)
📄 strtol.c(4.06 KB)
📄 strtoq.c(4.09 KB)
📄 strtoul.c(3.13 KB)
📄 strtouq.c(3.08 KB)
📄 strvalid.c(2.04 KB)
📄 timingsafe_bcmp.c(1.08 KB)
📄 ucmpdi2.c(2.32 KB)
📄 udivdi3.c(1.97 KB)
📄 umoddi3.c(2 KB)
📁 x86

Editing: strlen.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2009, 2010 Xin LI <delphij@FreeBSD.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/libkern.h>
#include <sys/limits.h>

/*
 * Portable strlen() for 32-bit and 64-bit systems.
 *
 * Rationale: it is generally much more efficient to do word length
 * operations and avoid branches on modern computer systems, as
 * compared to byte-length operations with a lot of branches.
 *
 * The expression:
 *
 *	((x - 0x01....01) & ~x & 0x80....80)
 *
 * would evaluate to a non-zero value iff any of the bytes in the
 * original word is zero.
 *
 * On multi-issue processors, we can divide the above expression into:
 *	a)  (x - 0x01....01)
 *	b) (~x & 0x80....80)
 *	c) a & b
 *
 * Where, a) and b) can be partially computed in parallel.
 *
 * The algorithm above is found on "Hacker's Delight" by
 * Henry S. Warren, Jr.
 */

/* Magic numbers for the algorithm */
#if LONG_BIT == 32
static const unsigned long mask01 = 0x01010101;
static const unsigned long mask80 = 0x80808080;
#elif LONG_BIT == 64
static const unsigned long mask01 = 0x0101010101010101;
static const unsigned long mask80 = 0x8080808080808080;
#else
#error Unsupported word size
#endif

#define	LONGPTR_MASK (sizeof(long) - 1)

/*
 * Helper macro to return string length if we caught the zero
 * byte.
 */
#define testbyte(x)				\
	do {					\
		if (p[x] == '\0')		\
		    return (p - str + x);	\
	} while (0)

size_t
(strlen)(const char *str)
{
	const char *p;
	const unsigned long *lp;
	long va, vb;

/*
	 * Before trying the hard (unaligned byte-by-byte access) way
	 * to figure out whether there is a nul character, try to see
	 * if there is a nul character is within this accessible word
	 * first.
	 *
	 * p and (p & ~LONGPTR_MASK) must be equally accessible since
	 * they always fall in the same memory page, as long as page
	 * boundaries is integral multiple of word size.
	 */
	lp = (const unsigned long *)((uintptr_t)str & ~LONGPTR_MASK);
	va = (*lp - mask01);
	vb = ((~*lp) & mask80);
	lp++;
	if (va & vb)
		/* Check if we have \0 in the first part */
		for (p = str; p < (const char *)lp; p++)
			if (*p == '\0')
				return (p - str);

/* Scan the rest of the string using word sized operation */
	for (; ; lp++) {
		va = (*lp - mask01);
		vb = ((~*lp) & mask80);
		if (va & vb) {
			p = (const char *)(lp);
			testbyte(0);
			testbyte(1);
			testbyte(2);
			testbyte(3);
#if (LONG_BIT >= 64)
			testbyte(4);
			testbyte(5);
			testbyte(6);
			testbyte(7);
#endif
		}
	}

/* NOTREACHED */
	return (0);
}

003 File Manager

Editing: strlen.c

Upload File

Create Folder