字符串函数实现---libstring.c

/*
* 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/module.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_STRCASECMP
int 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_STRNCASECMP
int 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 strcpy
char *strcpy（char *dest, const char *src）
{
char *tmp = dest;
while （（*dest++ = *src++）！= ""）
/* 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] = "";
}
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 strcat
char *strcat（char *dest, const char *src）
{
char *tmp = dest;
while （*dest）
dest++;
while （（*dest++ = *src++）！= ""）
;
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 = "";
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 strcmp
int 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 == ""）
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 ！= ""; ++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;
s = skip_spaces（s）;
size = strlen（s）;
if （！size）
return s;
end = s + size - 1;
while （end >= s && isspace（*end））
end--;
*（end + 1） = "";
return 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 ！= ""; ++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 ！= ""; ++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 ！= ""; ++p） {
for （a = accept; *a ！= ""; ++a） {
if （*p == *a）
break;
}
if （*a == ""）
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 ！= ""; ++p） {
for （r = reject; *r ！= ""; ++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 ！= ""; ++sc1） {
for （sc2 = ct; *sc2 ！= ""; ++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++ = "";
*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 == " " && ！s2[1]）
return true;
if （*s1 == " " && ！s1[1] && ！*s2）
return true;
return false;
}
EXPORT_SYMBOL（sysfs_streq）;
#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;