// SPDX-License-Identifier: GPL-2.0/* *  linux/lib/string.c * *  Copyright (C) 1991, 1992  Linus Torvalds */ /* * stupid library routines.. The optimized versions should generally be found * as inline code in <asm-xx/string.h> * * These are buggy as well.. * * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de> * -  Added strsep() which will replace strtok() soon (because strsep() is *    reentrant and should be faster). Use only strsep() in new code, please. * * * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>, *                    Matthew Hawkins <matt@mh.dropbear.id.au> * -  Kissed strtok() goodbye */ #include <linux/types.h>#include <linux/string.h>#include <linux/ctype.h>#include <linux/kernel.h>#include <linux/export.h>#include <linux/bug.h>#include <linux/errno.h>#include <linux/slab.h> #include <asm/byteorder.h>#include <asm/word-at-a-time.h>#include <asm/page.h> #ifndef __HAVE_ARCH_STRNCASECMP/** * strncasecmp - Case insensitive, length-limited string comparison * @s1: One string * @s2: The other string * @len: the maximum number of characters to compare */int strncasecmp(const char *s1, const char *s2, size_t len){	/* Yes, Virginia, it had better be unsigned */	unsigned char c1, c2; 	if (!len)		return 0; 	do {		c1 = *s1++;		c2 = *s2++;		if (!c1 || !c2)			break;		if (c1 == c2)			continue;		c1 = tolower(c1);		c2 = tolower(c2);		if (c1 != c2)			break;	} while (--len);	return (int)c1 - (int)c2;}EXPORT_SYMBOL(strncasecmp);#endif #ifndef __HAVE_ARCH_STRCASECMPint strcasecmp(const char *s1, const char *s2){	int c1, c2; 	do {		c1 = tolower(*s1++);		c2 = tolower(*s2++);	} while (c1 == c2 && c1 != 0);	return c1 - c2;}EXPORT_SYMBOL(strcasecmp);#endif #ifndef __HAVE_ARCH_STRCPY/** * strcpy - Copy a %NUL terminated string * @dest: Where to copy the string to * @src: Where to copy the string from */#undef strcpychar *strcpy(char *dest, const char *src){	char *tmp = dest; 	while ((*dest++ = *src++) != '\0')		/* nothing */;	return tmp;}EXPORT_SYMBOL(strcpy);#endif #ifndef __HAVE_ARCH_STRNCPY/** * strncpy - Copy a length-limited, C-string * @dest: Where to copy the string to * @src: Where to copy the string from * @count: The maximum number of bytes to copy * * The result is not %NUL-terminated if the source exceeds * @count bytes. * * In the case where the length of @src is less than  that  of * count, the remainder of @dest will be padded with %NUL. * */char *strncpy(char *dest, const char *src, size_t count){	char *tmp = dest; 	while (count) {		if ((*tmp = *src) != 0)			src++;		tmp++;		count--;	}	return dest;}EXPORT_SYMBOL(strncpy);#endif #ifndef __HAVE_ARCH_STRLCPY/** * strlcpy - Copy a C-string into a sized buffer * @dest: Where to copy the string to * @src: Where to copy the string from * @size: size of destination buffer * * Compatible with ``*BSD``: the result is always a valid * NUL-terminated string that fits in the buffer (unless, * of course, the buffer size is zero). It does not pad * out the result like strncpy() does. */size_t strlcpy(char *dest, const char *src, size_t size){	size_t ret = strlen(src); 	if (size) {		size_t len = (ret >= size) ? size - 1 : ret;		memcpy(dest, src, len);		dest[len] = '\0';	}	return ret;}EXPORT_SYMBOL(strlcpy);#endif #ifndef __HAVE_ARCH_STRSCPY/** * strscpy - Copy a C-string into a sized buffer * @dest: Where to copy the string to * @src: Where to copy the string from * @count: Size of destination buffer * * Copy the string, or as much of it as fits, into the dest buffer.  The * behavior is undefined if the string buffers overlap.  The destination * buffer is always NUL terminated, unless it's zero-sized. * * Preferred to strlcpy() since the API doesn't require reading memory * from the src string beyond the specified "count" bytes, and since * the return value is easier to error-check than strlcpy()'s. * In addition, the implementation is robust to the string changing out * from underneath it, unlike the current strlcpy() implementation. * * Preferred to strncpy() since it always returns a valid string, and * doesn't unnecessarily force the tail of the destination buffer to be * zeroed.  If zeroing is desired please use strscpy_pad(). * * Returns: * * The number of characters copied (not including the trailing %NUL) * * -E2BIG if count is 0 or @src was truncated. */ssize_t strscpy(char *dest, const char *src, size_t count){	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;	size_t max = count;	long res = 0; 	if (count == 0 || WARN_ON_ONCE(count > INT_MAX))		return -E2BIG; #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS	/*	 * If src is unaligned, don't cross a page boundary,	 * since we don't know if the next page is mapped.	 */	if ((long)src & (sizeof(long) - 1)) {		size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));		if (limit < max)			max = limit;	}#else	/* If src or dest is unaligned, don't do word-at-a-time. */	if (((long) dest | (long) src) & (sizeof(long) - 1))		max = 0;#endif 	while (max >= sizeof(unsigned long)) {		unsigned long c, data; 		c = read_word_at_a_time(src+res);		if (has_zero(c, &data, &constants)) {			data = prep_zero_mask(c, data, &constants);			data = create_zero_mask(data);			*(unsigned long *)(dest+res) = c & zero_bytemask(data);			return res + find_zero(data);		}		*(unsigned long *)(dest+res) = c;		res += sizeof(unsigned long);		count -= sizeof(unsigned long);		max -= sizeof(unsigned long);	} 	while (count) {		char c; 		c = src[res];		dest[res] = c;		if (!c)			return res;		res++;		count--;	} 	/* Hit buffer length without finding a NUL; force NUL-termination. */	if (res)		dest[res-1] = '\0'; 	return -E2BIG;}EXPORT_SYMBOL(strscpy);#endif /** * strscpy_pad() - Copy a C-string into a sized buffer * @dest: Where to copy the string to * @src: Where to copy the string from * @count: Size of destination buffer * * Copy the string, or as much of it as fits, into the dest buffer.  The * behavior is undefined if the string buffers overlap.  The destination * buffer is always %NUL terminated, unless it's zero-sized. * * If the source string is shorter than the destination buffer, zeros * the tail of the destination buffer. * * For full explanation of why you may want to consider using the * 'strscpy' functions please see the function docstring for strscpy(). * * Returns: * * The number of characters copied (not including the trailing %NUL) * * -E2BIG if count is 0 or @src was truncated. */ssize_t strscpy_pad(char *dest, const char *src, size_t count){	ssize_t written; 	written = strscpy(dest, src, count);	if (written < 0 || written == count - 1)		return written; 	memset(dest + written + 1, 0, count - written - 1); 	return written;}EXPORT_SYMBOL(strscpy_pad); #ifndef __HAVE_ARCH_STRCAT/** * strcat - Append one %NUL-terminated string to another * @dest: The string to be appended to * @src: The string to append to it */#undef strcatchar *strcat(char *dest, const char *src){	char *tmp = dest; 	while (*dest)		dest++;	while ((*dest++ = *src++) != '\0')		;	return tmp;}EXPORT_SYMBOL(strcat);#endif #ifndef __HAVE_ARCH_STRNCAT/** * strncat - Append a length-limited, C-string to another * @dest: The string to be appended to * @src: The string to append to it * @count: The maximum numbers of bytes to copy * * Note that in contrast to strncpy(), strncat() ensures the result is * terminated. */char *strncat(char *dest, const char *src, size_t count){	char *tmp = dest; 	if (count) {		while (*dest)			dest++;		while ((*dest++ = *src++) != 0) {			if (--count == 0) {				*dest = '\0';				break;			}		}	}	return tmp;}EXPORT_SYMBOL(strncat);#endif #ifndef __HAVE_ARCH_STRLCAT/** * strlcat - Append a length-limited, C-string to another * @dest: The string to be appended to * @src: The string to append to it * @count: The size of the destination buffer. */size_t strlcat(char *dest, const char *src, size_t count){	size_t dsize = strlen(dest);	size_t len = strlen(src);	size_t res = dsize + len; 	/* This would be a bug */	BUG_ON(dsize >= count); 	dest += dsize;	count -= dsize;	if (len >= count)		len = count-1;	memcpy(dest, src, len);	dest[len] = 0;	return res;}EXPORT_SYMBOL(strlcat);#endif #ifndef __HAVE_ARCH_STRCMP/** * strcmp - Compare two strings * @cs: One string * @ct: Another string */#undef strcmpint strcmp(const char *cs, const char *ct){	unsigned char c1, c2; 	while (1) {		c1 = *cs++;		c2 = *ct++;		if (c1 != c2)			return c1 < c2 ? -1 : 1;		if (!c1)			break;	}	return 0;}EXPORT_SYMBOL(strcmp);#endif #ifndef __HAVE_ARCH_STRNCMP/** * strncmp - Compare two length-limited strings * @cs: One string * @ct: Another string * @count: The maximum number of bytes to compare */int strncmp(const char *cs, const char *ct, size_t count){	unsigned char c1, c2; 	while (count) {		c1 = *cs++;		c2 = *ct++;		if (c1 != c2)			return c1 < c2 ? -1 : 1;		if (!c1)			break;		count--;	}	return 0;}EXPORT_SYMBOL(strncmp);#endif #ifndef __HAVE_ARCH_STRCHR/** * strchr - Find the first occurrence of a character in a string * @s: The string to be searched * @c: The character to search for * * Note that the %NUL-terminator is considered part of the string, and can * be searched for. */char *strchr(const char *s, int c){	for (; *s != (char)c; ++s)		if (*s == '\0')			return NULL;	return (char *)s;}EXPORT_SYMBOL(strchr);#endif #ifndef __HAVE_ARCH_STRCHRNUL/** * strchrnul - Find and return a character in a string, or end of string * @s: The string to be searched * @c: The character to search for * * Returns pointer to first occurrence of 'c' in s. If c is not found, then * return a pointer to the null byte at the end of s. */char *strchrnul(const char *s, int c){	while (*s && *s != (char)c)		s++;	return (char *)s;}EXPORT_SYMBOL(strchrnul);#endif /** * strnchrnul - Find and return a character in a length limited string, * or end of string * @s: The string to be searched * @count: The number of characters to be searched * @c: The character to search for * * Returns pointer to the first occurrence of 'c' in s. If c is not found, * then return a pointer to the last character of the string. */char *strnchrnul(const char *s, size_t count, int c){	while (count-- && *s && *s != (char)c)		s++;	return (char *)s;} #ifndef __HAVE_ARCH_STRRCHR/** * strrchr - Find the last occurrence of a character in a string * @s: The string to be searched * @c: The character to search for */char *strrchr(const char *s, int c){	const char *last = NULL;	do {		if (*s == (char)c)			last = s;	} while (*s++);	return (char *)last;}EXPORT_SYMBOL(strrchr);#endif #ifndef __HAVE_ARCH_STRNCHR/** * strnchr - Find a character in a length limited string * @s: The string to be searched * @count: The number of characters to be searched * @c: The character to search for * * Note that the %NUL-terminator is considered part of the string, and can * be searched for. */char *strnchr(const char *s, size_t count, int c){	while (count--) {		if (*s == (char)c)			return (char *)s;		if (*s++ == '\0')			break;	}	return NULL;}EXPORT_SYMBOL(strnchr);#endif /** * skip_spaces - Removes leading whitespace from @str. * @str: The string to be stripped. * * Returns a pointer to the first non-whitespace character in @str. */

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