c语言string源码

#ifndef _LINUX_STRING_H_#define _LINUX_STRING_H_/* We don't want strings.h stuff being used by user stuff by accident */#ifndef __KERNEL__#include <string.h>#else#include <linux/compiler.h>/* for inline */#include <linux/types.h>/* for size_t */#include <linux/stddef.h>/* for NULL */#include <stdarg.h>extern char *strndup_user(const char __user *, long);extern void *memdup_user(const void __user *, size_t);/* * Include machine specific inline routines */#include <asm/string.h>#ifndef __HAVE_ARCH_STRCPYextern char * strcpy(char *,const char *);#endif#ifndef __HAVE_ARCH_STRNCPYextern char * strncpy(char *,const char *, __kernel_size_t);#endif#ifndef __HAVE_ARCH_STRLCPYsize_t strlcpy(char *, const char *, size_t);#endif#ifndef __HAVE_ARCH_STRCATextern char * strcat(char *, const char *);#endif#ifndef __HAVE_ARCH_STRNCATextern char * strncat(char *, const char *, __kernel_size_t);#endif#ifndef __HAVE_ARCH_STRLCATextern size_t strlcat(char *, const char *, __kernel_size_t);#endif#ifndef __HAVE_ARCH_STRCMPextern int strcmp(const char *,const char *);#endif#ifndef __HAVE_ARCH_STRNCMPextern int strncmp(const char *,const char *,__kernel_size_t);#endif#ifndef __HAVE_ARCH_STRNICMPextern int strnicmp(const char *, const char *, __kernel_size_t);#endif#ifndef __HAVE_ARCH_STRCASECMPextern int strcasecmp(const char *s1, const char *s2);#endif#ifndef __HAVE_ARCH_STRNCASECMPextern int strncasecmp(const char *s1, const char *s2, size_t n);#endif#ifndef __HAVE_ARCH_STRCHRextern char * strchr(const char *,int);#endif#ifndef __HAVE_ARCH_STRNCHRextern char * strnchr(const char *, size_t, int);#endif#ifndef __HAVE_ARCH_STRRCHRextern char * strrchr(const char *,int);#endifextern char * __must_check skip_spaces(const char *);extern char *strim(char *);static inline __must_check char *strstrip(char *str){return strim(str);}#ifndef __HAVE_ARCH_STRSTRextern char * strstr(const char *, const char *);#endif#ifndef __HAVE_ARCH_STRNSTRextern char * strnstr(const char *, const char *, size_t);#endif#ifndef __HAVE_ARCH_STRLENextern __kernel_size_t strlen(const char *);#endif#ifndef __HAVE_ARCH_STRNLENextern __kernel_size_t strnlen(const char *,__kernel_size_t);#endif#ifndef __HAVE_ARCH_STRPBRKextern char * strpbrk(const char *,const char *);#endif#ifndef __HAVE_ARCH_STRSEPextern char * strsep(char **,const char *);#endif#ifndef __HAVE_ARCH_STRSPNextern __kernel_size_t strspn(const char *,const char *);#endif#ifndef __HAVE_ARCH_STRCSPNextern __kernel_size_t strcspn(const char *,const char *);#endif#ifndef __HAVE_ARCH_MEMSETextern void * memset(void *,int,__kernel_size_t);#endif#ifndef __HAVE_ARCH_MEMCPYextern void * memcpy(void *,const void *,__kernel_size_t);#endif#ifndef __HAVE_ARCH_MEMMOVEextern void * memmove(void *,const void *,__kernel_size_t);#endif#ifndef __HAVE_ARCH_MEMSCANextern void * memscan(void *,int,__kernel_size_t);#endif#ifndef __HAVE_ARCH_MEMCMPextern int memcmp(const void *,const void *,__kernel_size_t);#endif#ifndef __HAVE_ARCH_MEMCHRextern void * memchr(const void *,int,__kernel_size_t);#endifvoid *memchr_inv(const void *s, int c, size_t n);extern char *kstrdup(const char *s, gfp_t gfp);extern char *kstrndup(const char *s, size_t len, gfp_t gfp);extern void *kmemdup(const void *src, size_t len, gfp_t gfp);extern char **argv_split(gfp_t gfp, const char *str, int *argcp);extern void argv_free(char **argv);extern bool sysfs_streq(const char *s1, const char *s2);extern int strtobool(const char *s, bool *res);#ifdef CONFIG_BINARY_PRINTFint vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf);int bprintf(u32 *bin_buf, size_t size, const char *fmt, ...) __printf(3, 4);#endifextern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,const void *from, size_t available);/** * strstarts - does @str start with @prefix? * @str: string to examine * @prefix: prefix to look for. */static inline bool strstarts(const char *str, const char *prefix){return strncmp(str, prefix, strlen(prefix)) == 0;}extern size_t memweight(const void *ptr, size_t bytes);#endif /* __KERNEL__ */#endif /* _LINUX_STRING_H_ */

/* *  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 <[e-mail]> * -  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 <[e-mail]>, *                    Matthew Hawkins <[e-mail]> * -  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>#ifndef __HAVE_ARCH_STRNICMP/** * strnicmp - Case insensitive, length-limited string comparison * @s1: One string * @s2: The other string * @len: the maximum number of characters to compare */int strnicmp(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(strnicmp);#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_STRNCASECMPint strncasecmp(const char *s1, const char *s2, size_t n){int c1, c2;do {c1 = tolower(*s1++);c2 = tolower(*s2++);} while ((--n > 0) && c1 == c2 && c1 != 0);return c1 - c2;}EXPORT_SYMBOL(strncasecmp);#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, %NUL-terminated 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 %NUL terminated 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_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, %NUL-terminated 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, %NUL-terminated 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 */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_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 *p = s + strlen(s);       do {           if (*p == (char)c)               return (char *)p;       } while (--p >= s);       return NULL;}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 */char *strnchr(const char *s, size_t count, int c){for (; count-- && *s != '\0'; ++s)if (*s == (char)c)return (char *)s;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. */char *skip_spaces(const char *str){while (isspace(*str))++str;return (char *)str;}EXPORT_SYMBOL(skip_spaces);/** * strim - Removes leading and trailing whitespace from @s. * @s: The string to be stripped. * * Note that the first trailing whitespace is replaced with a %NUL-terminator * in the given string @s. Returns a pointer to the first non-whitespace * character in @s. */char *strim(char *s){size_t size;char *end;size = strlen(s);if (!size)return s;end = s + size - 1;while (end >= s && isspace(*end))end--;*(end + 1) = '\0';return skip_spaces(s);}EXPORT_SYMBOL(strim);#ifndef __HAVE_ARCH_STRLEN/** * strlen - Find the length of a string * @s: The string to be sized */size_t strlen(const char *s){const char *sc;for (sc = s; *sc != '\0'; ++sc)/* nothing */;return sc - s;}EXPORT_SYMBOL(strlen);#endif#ifndef __HAVE_ARCH_STRNLEN/** * strnlen - Find the length of a length-limited string * @s: The string to be sized * @count: The maximum number of bytes to search */size_t strnlen(const char *s, size_t count){const char *sc;for (sc = s; count-- && *sc != '\0'; ++sc)/* nothing */;return sc - s;}EXPORT_SYMBOL(strnlen);#endif#ifndef __HAVE_ARCH_STRSPN/** * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept * @s: The string to be searched * @accept: The string to search for */size_t strspn(const char *s, const char *accept){const char *p;const char *a;size_t count = 0;for (p = s; *p != '\0'; ++p) {for (a = accept; *a != '\0'; ++a) {if (*p == *a)break;}if (*a == '\0')return count;++count;}return count;}EXPORT_SYMBOL(strspn);#endif#ifndef __HAVE_ARCH_STRCSPN/** * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject * @s: The string to be searched * @reject: The string to avoid */size_t strcspn(const char *s, const char *reject){const char *p;const char *r;size_t count = 0;for (p = s; *p != '\0'; ++p) {for (r = reject; *r != '\0'; ++r) {if (*p == *r)return count;}++count;}return count;}EXPORT_SYMBOL(strcspn);#endif#ifndef __HAVE_ARCH_STRPBRK/** * strpbrk - Find the first occurrence of a set of characters * @cs: The string to be searched * @ct: The characters to search for */char *strpbrk(const char *cs, const char *ct){const char *sc1, *sc2;for (sc1 = cs; *sc1 != '\0'; ++sc1) {for (sc2 = ct; *sc2 != '\0'; ++sc2) {if (*sc1 == *sc2)return (char *)sc1;}}return NULL;}EXPORT_SYMBOL(strpbrk);#endif#ifndef __HAVE_ARCH_STRSEP/** * strsep - Split a string into tokens * @s: The string to be searched * @ct: The characters to search for * * strsep() updates @s to point after the token, ready for the next call. * * It returns empty tokens, too, behaving exactly like the libc function * of that name. In fact, it was stolen from glibc2 and de-fancy-fied. * Same semantics, slimmer shape. ;) */char *strsep(char **s, const char *ct){char *sbegin = *s;char *end;if (sbegin == NULL)return NULL;end = strpbrk(sbegin, ct);if (end)*end++ = '\0';*s = end;return sbegin;}EXPORT_SYMBOL(strsep);#endif/** * sysfs_streq - return true if strings are equal, modulo trailing newline * @s1: one string * @s2: another string * * This routine returns true iff two strings are equal, treating both * NUL and newline-then-NUL as equivalent string terminations.  It's * geared for use with sysfs input strings, which generally terminate * with newlines but are compared against values without newlines. */bool sysfs_streq(const char *s1, const char *s2){while (*s1 && *s1 == *s2) {s1++;s2++;}if (*s1 == *s2)return true;if (!*s1 && *s2 == '\n' && !s2[1])return true;if (*s1 == '\n' && !s1[1] && !*s2)return true;return false;}EXPORT_SYMBOL(sysfs_streq);/** * strtobool - convert common user inputs into boolean values * @s: input string * @res: result * * This routine returns 0 iff the first character is one of 'Yy1Nn0'. * Otherwise it will return -EINVAL.  Value pointed to by res is * updated upon finding a match. */int strtobool(const char *s, bool *res){switch (s[0]) {case 'y':case 'Y':case '1':*res = true;break;case 'n':case 'N':case '0':*res = false;break;default:return -EINVAL;}return 0;}EXPORT_SYMBOL(strtobool);#ifndef __HAVE_ARCH_MEMSET/** * memset - Fill a region of memory with the given value * @s: Pointer to the start of the area. * @c: The byte to fill the area with * @count: The size of the area. * * Do not use memset() to access IO space, use memset_io() instead. */void *memset(void *s, int c, size_t count){char *xs = s;while (count--)*xs++ = c;return s;}EXPORT_SYMBOL(memset);#endif#ifndef __HAVE_ARCH_MEMCPY/** * memcpy - Copy one area of memory to another * @dest: Where to copy to * @src: Where to copy from * @count: The size of the area. * * You should not use this function to access IO space, use memcpy_toio() * or memcpy_fromio() instead. */void *memcpy(void *dest, const void *src, size_t count){char *tmp = dest;const char *s = src;while (count--)*tmp++ = *s++;return dest;}EXPORT_SYMBOL(memcpy);#endif#ifndef __HAVE_ARCH_MEMMOVE/** * memmove - Copy one area of memory to another * @dest: Where to copy to * @src: Where to copy from * @count: The size of the area. * * Unlike memcpy(), memmove() copes with overlapping areas. */void *memmove(void *dest, const void *src, size_t count){char *tmp;const char *s;if (dest <= src) {tmp = dest;s = src;while (count--)*tmp++ = *s++;} else {tmp = dest;tmp += count;s = src;s += count;while (count--)*--tmp = *--s;}return dest;}EXPORT_SYMBOL(memmove);#endif#ifndef __HAVE_ARCH_MEMCMP/** * memcmp - Compare two areas of memory * @cs: One area of memory * @ct: Another area of memory * @count: The size of the area. */#undef memcmpint memcmp(const void *cs, const void *ct, size_t count){const unsigned char *su1, *su2;int res = 0;for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)if ((res = *su1 - *su2) != 0)break;return res;}EXPORT_SYMBOL(memcmp);#endif#ifndef __HAVE_ARCH_MEMSCAN/** * memscan - Find a character in an area of memory. * @addr: The memory area * @c: The byte to search for * @size: The size of the area. * * returns the address of the first occurrence of @c, or 1 byte past * the area if @c is not found */void *memscan(void *addr, int c, size_t size){unsigned char *p = addr;while (size) {if (*p == c)return (void *)p;p++;size--;}  return (void *)p;}EXPORT_SYMBOL(memscan);#endif#ifndef __HAVE_ARCH_STRSTR/** * strstr - Find the first substring in a %NUL terminated string * @s1: The string to be searched * @s2: The string to search for */char *strstr(const char *s1, const char *s2){size_t l1, l2;l2 = strlen(s2);if (!l2)return (char *)s1;l1 = strlen(s1);while (l1 >= l2) {l1--;if (!memcmp(s1, s2, l2))return (char *)s1;s1++;}return NULL;}EXPORT_SYMBOL(strstr);#endif#ifndef __HAVE_ARCH_STRNSTR/** * strnstr - Find the first substring in a length-limited string * @s1: The string to be searched * @s2: The string to search for * @len: the maximum number of characters to search */char *strnstr(const char *s1, const char *s2, size_t len){size_t l2;l2 = strlen(s2);if (!l2)return (char *)s1;while (len >= l2) {len--;if (!memcmp(s1, s2, l2))return (char *)s1;s1++;}return NULL;}EXPORT_SYMBOL(strnstr);#endif#ifndef __HAVE_ARCH_MEMCHR/** * memchr - Find a character in an area of memory. * @s: The memory area * @c: The byte to search for * @n: The size of the area. * * returns the address of the first occurrence of @c, or %NULL * if @c is not found */void *memchr(const void *s, int c, size_t n){const unsigned char *p = s;while (n-- != 0) {        if ((unsigned char)c == *p++) {return (void *)(p - 1);}}return NULL;}EXPORT_SYMBOL(memchr);#endifstatic void *check_bytes8(const u8 *start, u8 value, unsigned int bytes){while (bytes) {if (*start != value)return (void *)start;start++;bytes--;}return NULL;}/** * memchr_inv - Find an unmatching character in an area of memory. * @start: The memory area * @c: Find a character other than c * @bytes: The size of the area. * * returns the address of the first character other than @c, or %NULL * if the whole buffer contains just @c. */void *memchr_inv(const void *start, int c, size_t bytes){u8 value = c;u64 value64;unsigned int words, prefix;if (bytes <= 16)return check_bytes8(start, value, bytes);value64 = value;#if defined(ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64value64 *= 0x0101010101010101;#elif defined(ARCH_HAS_FAST_MULTIPLIER)value64 *= 0x01010101;value64 |= value64 << 32;#elsevalue64 |= value64 << 8;value64 |= value64 << 16;value64 |= value64 << 32;#endifprefix = (unsigned long)start % 8;if (prefix) {u8 *r;prefix = 8 - prefix;r = check_bytes8(start, value, prefix);if (r)return r;start += prefix;bytes -= prefix;}words = bytes / 8;while (words) {if (*(u64 *)start != value64)return check_bytes8(start, value, 8);start += 8;words--;}return check_bytes8(start, value, bytes % 8);}EXPORT_SYMBOL(memchr_inv);