1 // SPDX-License-Identifier: GPL-2.0
3 * Optimized string functions
6 * Copyright IBM Corp. 2004
7 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
10 #define IN_ARCH_STRING_C 1
12 #include <linux/types.h>
13 #include <linux/string.h>
14 #include <linux/export.h>
17 * Helper functions to find the end of a string
19 static inline char *__strend(const char *s)
27 : [e] "+&a" (e), [s] "+&a" (s)
29 : "cc", "memory", "0");
33 static inline char *__strnend(const char *s, size_t n)
35 const char *p = s + n;
41 : [p] "+&d" (p), [s] "+&a" (s)
43 : "cc", "memory", "0");
48 * strlen - Find the length of a string
49 * @s: The string to be sized
51 * returns the length of @s
53 #ifdef __HAVE_ARCH_STRLEN
54 size_t strlen(const char *s)
56 return __strend(s) - s;
58 EXPORT_SYMBOL(strlen);
62 * strnlen - Find the length of a length-limited string
63 * @s: The string to be sized
64 * @n: The maximum number of bytes to search
66 * returns the minimum of the length of @s and @n
68 #ifdef __HAVE_ARCH_STRNLEN
69 size_t strnlen(const char *s, size_t n)
71 return __strnend(s, n) - s;
73 EXPORT_SYMBOL(strnlen);
77 * strcpy - Copy a %NUL terminated string
78 * @dest: Where to copy the string to
79 * @src: Where to copy the string from
81 * returns a pointer to @dest
83 #ifdef __HAVE_ARCH_STRCPY
84 char *strcpy(char *dest, const char *src)
90 "0: mvst %[dest],%[src]\n"
92 : [dest] "+&a" (dest), [src] "+&a" (src)
94 : "cc", "memory", "0");
97 EXPORT_SYMBOL(strcpy);
101 * strlcpy - Copy a %NUL terminated string into a sized buffer
102 * @dest: Where to copy the string to
103 * @src: Where to copy the string from
104 * @size: size of destination buffer
106 * Compatible with *BSD: the result is always a valid
107 * NUL-terminated string that fits in the buffer (unless,
108 * of course, the buffer size is zero). It does not pad
109 * out the result like strncpy() does.
111 #ifdef __HAVE_ARCH_STRLCPY
112 size_t strlcpy(char *dest, const char *src, size_t size)
114 size_t ret = __strend(src) - src;
117 size_t len = (ret >= size) ? size-1 : ret;
119 memcpy(dest, src, len);
123 EXPORT_SYMBOL(strlcpy);
127 * strncpy - Copy a length-limited, %NUL-terminated string
128 * @dest: Where to copy the string to
129 * @src: Where to copy the string from
130 * @n: The maximum number of bytes to copy
132 * The result is not %NUL-terminated if the source exceeds
135 #ifdef __HAVE_ARCH_STRNCPY
136 char *strncpy(char *dest, const char *src, size_t n)
138 size_t len = __strnend(src, n) - src;
139 memset(dest + len, 0, n - len);
140 memcpy(dest, src, len);
143 EXPORT_SYMBOL(strncpy);
147 * strcat - Append one %NUL-terminated string to another
148 * @dest: The string to be appended to
149 * @src: The string to append to it
151 * returns a pointer to @dest
153 #ifdef __HAVE_ARCH_STRCAT
154 char *strcat(char *dest, const char *src)
156 unsigned long dummy = 0;
161 "0: srst %[dummy],%[dest]\n"
163 "1: mvst %[dummy],%[src]\n"
165 : [dummy] "+&a" (dummy), [dest] "+&a" (dest), [src] "+&a" (src)
167 : "cc", "memory", "0");
170 EXPORT_SYMBOL(strcat);
174 * strlcat - Append a length-limited, %NUL-terminated string to another
175 * @dest: The string to be appended to
176 * @src: The string to append to it
177 * @n: The size of the destination buffer.
179 #ifdef __HAVE_ARCH_STRLCAT
180 size_t strlcat(char *dest, const char *src, size_t n)
182 size_t dsize = __strend(dest) - dest;
183 size_t len = __strend(src) - src;
184 size_t res = dsize + len;
192 memcpy(dest, src, len);
196 EXPORT_SYMBOL(strlcat);
200 * strncat - Append a length-limited, %NUL-terminated string to another
201 * @dest: The string to be appended to
202 * @src: The string to append to it
203 * @n: The maximum numbers of bytes to copy
205 * returns a pointer to @dest
207 * Note that in contrast to strncpy, strncat ensures the result is
210 #ifdef __HAVE_ARCH_STRNCAT
211 char *strncat(char *dest, const char *src, size_t n)
213 size_t len = __strnend(src, n) - src;
214 char *p = __strend(dest);
220 EXPORT_SYMBOL(strncat);
224 * strcmp - Compare two strings
226 * @s2: Another string
228 * returns 0 if @s1 and @s2 are equal,
229 * < 0 if @s1 is less than @s2
230 * > 0 if @s1 is greater than @s2
232 #ifdef __HAVE_ARCH_STRCMP
233 int strcmp(const char *s1, const char *s2)
239 "0: clst %[s1],%[s2]\n"
242 " ic %[ret],0(%[s1])\n"
246 : [ret] "+&d" (ret), [s1] "+&a" (s1), [s2] "+&a" (s2)
248 : "cc", "memory", "0");
251 EXPORT_SYMBOL(strcmp);
255 * strrchr - Find the last occurrence of a character in a string
256 * @s: The string to be searched
257 * @c: The character to search for
259 #ifdef __HAVE_ARCH_STRRCHR
260 char *strrchr(const char *s, int c)
262 ssize_t len = __strend(s) - s;
265 if (s[len] == (char)c)
266 return (char *)s + len;
267 } while (--len >= 0);
270 EXPORT_SYMBOL(strrchr);
273 static inline int clcle(const char *s1, unsigned long l1,
274 const char *s2, unsigned long l2)
276 union register_pair r1 = { .even = (unsigned long)s1, .odd = l1, };
277 union register_pair r3 = { .even = (unsigned long)s2, .odd = l2, };
281 "0: clcle %[r1],%[r3],0\n"
285 : [cc] "=&d" (cc), [r1] "+&d" (r1.pair), [r3] "+&d" (r3.pair)
292 * strstr - Find the first substring in a %NUL terminated string
293 * @s1: The string to be searched
294 * @s2: The string to search for
296 #ifdef __HAVE_ARCH_STRSTR
297 char *strstr(const char *s1, const char *s2)
301 l2 = __strend(s2) - s2;
304 l1 = __strend(s1) - s1;
308 cc = clcle(s1, l2, s2, l2);
315 EXPORT_SYMBOL(strstr);
319 * memchr - Find a character in an area of memory.
320 * @s: The memory area
321 * @c: The byte to search for
322 * @n: The size of the area.
324 * returns the address of the first occurrence of @c, or %NULL
327 #ifdef __HAVE_ARCH_MEMCHR
328 void *memchr(const void *s, int c, size_t n)
330 const void *ret = s + n;
334 "0: srst %[ret],%[s]\n"
339 : [ret] "+&a" (ret), [s] "+&a" (s)
341 : "cc", "memory", "0");
344 EXPORT_SYMBOL(memchr);
348 * memcmp - Compare two areas of memory
349 * @s1: One area of memory
350 * @s2: Another area of memory
351 * @n: The size of the area.
353 #ifdef __HAVE_ARCH_MEMCMP
354 int memcmp(const void *s1, const void *s2, size_t n)
358 ret = clcle(s1, n, s2, n);
360 ret = ret == 1 ? -1 : 1;
363 EXPORT_SYMBOL(memcmp);
367 * memscan - Find a character in an area of memory.
368 * @s: The memory area
369 * @c: The byte to search for
370 * @n: The size of the area.
372 * returns the address of the first occurrence of @c, or 1 byte past
373 * the area if @c is not found
375 #ifdef __HAVE_ARCH_MEMSCAN
376 void *memscan(void *s, int c, size_t n)
378 const void *ret = s + n;
382 "0: srst %[ret],%[s]\n"
384 : [ret] "+&a" (ret), [s] "+&a" (s)
386 : "cc", "memory", "0");
389 EXPORT_SYMBOL(memscan);