Linux下string操作的精彩源码欣赏

/*
* 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.
*/

#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>

#ifndef __HAVE_ARCH_STRNICMP
int strnicmp(const char *s1, const char *s2, size_t len)
{
/* Yes, Virginia, it had better be unsigned */
unsigned char c1, c2;

c1 = 0; c2 = 0;
if (len) {
do {
c1 = *s1; c2 = *s2;
s1++; s2++;
if (!c1)
break;
if (!c2)
break;
if (c1 == c2)
continue;
c1 = tolower(c1);
c2 = tolower(c2);
if (c1 != c2)
break;
} while (--len);
}
return (int)c1 - (int)c2;
}
#endif

char * ___strtok;

#ifndef __HAVE_ARCH_STRCPY
char * strcpy(char * dest,const char *src)
{
char *tmp = dest;

while ((*dest++ = *src++) != '/0')
/* nothing */;
return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRNCPY
char * strncpy(char * dest,const char *src,size_t count)
{
char *tmp = dest;

while (count-- && (*dest++ = *src++) != '/0')
/* nothing */;

return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRCAT
char * strcat(char * dest, const char * src)
{
char *tmp = dest;

while (*dest)
dest++;
while ((*dest++ = *src++) != '/0')
;

return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRNCAT
char * strncat(char *dest, const char *src, size_t count)
{
char *tmp = dest;

if (count) {
while (*dest)
dest++;
while ((*dest++ = *src++)) {
if (--count == 0) {
*dest = '/0';
break;
}
}
}

return tmp;
}
#endif

#ifndef __HAVE_ARCH_STRCMP
int strcmp(const char * cs,const char * ct)
{
register signed char __res;

while (1) {
if ((__res = *cs - *ct++) != 0 || !*cs++)
break;
}

return __res;
}
#endif

#ifndef __HAVE_ARCH_STRNCMP
int strncmp(const char * cs,const char * ct,size_t count)
{
register signed char __res = 0;

while (count) {
if ((__res = *cs - *ct++) != 0 || !*cs++)
break;
count--;
}

return __res;
}
#endif

#ifndef __HAVE_ARCH_STRCHR
char * strchr(const char * s, int c)
{
for(; *s != (char) c; ++s)
if (*s == '/0')
return NULL;
return (char *) s;
}
#endif

#ifndef __HAVE_ARCH_STRRCHR
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;
}
#endif

#ifndef __HAVE_ARCH_STRLEN
size_t strlen(const char * s)
{
const char *sc;

for (sc = s; *sc != '/0'; ++sc)
/* nothing */;
return sc - s;
}
#endif

#ifndef __HAVE_ARCH_STRNLEN
size_t strnlen(const char * s, size_t count)
{
const char *sc;

for (sc = s; count-- && *sc != '/0'; ++sc)
/* nothing */;
return sc - s;
}
#endif

#ifndef __HAVE_ARCH_STRSPN
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;
}
#endif

#ifndef __HAVE_ARCH_STRPBRK
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;
}
#endif

#ifndef __HAVE_ARCH_STRTOK
char * strtok(char * s,const char * ct)
{
char *sbegin, *send;

sbegin = s ? s : ___strtok;
if (!sbegin) {
return NULL;
}
sbegin += strspn(sbegin,ct);
if (*sbegin == '/0') {
___strtok = NULL;
return( NULL );
}
send = strpbrk( sbegin, ct);
if (send && *send != '/0')
*send++ = '/0';
___strtok = send;
return (sbegin);
}
#endif

#ifndef __HAVE_ARCH_STRSEP

char * strsep(char **s, const char * ct)
{
char *sbegin=*s;
if (!sbegin)
return NULL;

sbegin += strspn(sbegin,ct);
if (*sbegin == '/0')
return NULL;

*s = strpbrk( sbegin, ct);
if (*s && **s != '/0')
*(*s)++ = '/0';
return (sbegin);
}
#endif

#ifndef __HAVE_ARCH_MEMSET
void * memset(void * s,int c,size_t count)
{
char *xs = (char *) s;

while (count--)
*xs++ = c;

return s;
}
#endif

#ifndef __HAVE_ARCH_BCOPY
char * bcopy(const char * src, char * dest, int count)
{
char *tmp = dest;

while (count--)
*tmp++ = *src++;

return dest;
}
#endif

#ifndef __HAVE_ARCH_MEMCPY
void * memcpy(void * dest,const void *src,size_t count)
{
char *tmp = (char *) dest, *s = (char *) src;

while (count--)
*tmp++ = *s++;

return dest;
}
#endif

#ifndef __HAVE_ARCH_MEMMOVE
void * memmove(void * dest,const void *src,size_t count)
{
char *tmp, *s;

if (dest <= src) {
tmp = (char *) dest;
s = (char *) src;
while (count--)
*tmp++ = *s++;
}
else {
tmp = (char *) dest + count;
s = (char *) src + count;
while (count--)
*--tmp = *--s;
}

return dest;
}
#endif

#ifndef __HAVE_ARCH_MEMCMP
int memcmp(const void * cs,const void * ct,size_t count)
{
const unsigned char *su1, *su2;
signed char res = 0;

for( su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
if ((res = *su1 - *su2) != 0)
break;
return res;
}
#endif

/*
* find the first occurrence of byte 'c', or 1 past the area if none
*/
#ifndef __HAVE_ARCH_MEMSCAN
void * memscan(void * addr, int c, size_t size)
{
unsigned char * p = (unsigned char *) addr;

while (size) {
if (*p == c)
return (void *) p;
p++;
size--;
}
return (void *) p;
}
#endif

#ifndef __HAVE_ARCH_STRSTR
char * strstr(const char * s1,const char * s2)
{
int 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;
}
#endif

#ifndef __HAVE_ARCH_MEMCHR
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;
}

#endif