lib/libutils/isoc/newlib/strlen.c

// SPDX-License-Identifier: BSD-3-Clause
/*
 * Copyright (c) 1994-2009  Red Hat, Inc.
 * All rights reserved.
 *
 * 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.
 *
 * 3. Neither the name of the copyright holder nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 */

/* This file is copied from newlib-1.19 */

/*
FUNCTION
	<<strlen>>---character string length

INDEX
	strlen

ANSI_SYNOPSIS
	#include <string.h>
	size_t strlen(const char *<[str]>);

TRAD_SYNOPSIS
	#include <string.h>
	size_t strlen(<[str]>)
	char *<[src]>;

DESCRIPTION
	The <<strlen>> function works out the length of the string
	starting at <<*<[str]>>> by counting chararacters until it
	reaches a <<NULL>> character.

RETURNS
	<<strlen>> returns the character count.

PORTABILITY
<<strlen>> is ANSI C.

<<strlen>> requires no supporting OS subroutines.

QUICKREF
	strlen ansi pure
*/

#include "_ansi.h"
#include <string.h>
#include <limits.h>

#define LBLOCKSIZE   (sizeof(long))
#define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))

#if LONG_MAX == 2147483647L
#define DETECTNULL(X) (((X) - 0x01010101L) & ~(X) & 0x80808080UL)
#else
#if LONG_MAX == 9223372036854775807L
/* Nonzero if X (a long int) contains a NULL byte. */
#define DETECTNULL(X) (((X) - 0x0101010101010101L) & ~(X) & \
		       0x8080808080808080UL)
#else
#error long int is not a 32bit or 64bit type.
#endif
#endif

#ifndef DETECTNULL
#error long int is not a 32bit or 64bit byte
#endif

size_t _DEFUN(strlen, (str), _CONST char *str)
{
	_CONST char *start = str;

#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
	unsigned long *aligned_addr;

	/* Align the pointer, so we can search a word at a time.  */
	while (UNALIGNED(str)) {
		if (!*str)
			return str - start;
		str++;
	}

	/* If the string is word-aligned, we can check for the presence of
	   a null in each word-sized block.  */
	aligned_addr = (unsigned long *)str;
	while (!DETECTNULL(*aligned_addr))
		aligned_addr++;

	/* Once a null is detected, we check each byte in that block for a
	   precise position of the null.  */
	str = (char *)aligned_addr;

#endif /* not PREFER_SIZE_OVER_SPEED */

	while (*str)
		str++;
	return str - start;
}