LINUX下字符串操作函数的源代码

static inline char * strcpy(char * dest,const char *src)
{
int d0, d1, d2;
__asm__ __volatile__(
"1:/tlodsb/n/t"
"stosb/n/t"
"testb %%al,%%al/n/t"
"jne 1b"
: "=&S" (d0), "=&D" (d1), "=&a" (d2)
:"0" (src),"1" (dest) : "memory");
return dest;
}

static inline char * strncpy(char * dest,const char *src,size_t count)
{
int d0, d1, d2, d3;
__asm__ __volatile__(
"1:/tdecl %2/n/t"
"js 2f/n/t"
"lodsb/n/t"
"stosb/n/t"
"testb %%al,%%al/n/t"
"jne 1b/n/t"
"rep/n/t"
"stosb/n"
"2:"
: "=&S" (d0), "=&D" (d1), "=&c" (d2), "=&a" (d3)
:"0" (src),"1" (dest),"2" (count) : "memory");
return dest;
}

static inline char * strcat(char * dest,const char * src)
{
int d0, d1, d2, d3;
__asm__ __volatile__(
"repne/n/t"
"scasb/n/t"
"decl %1/n"
"1:/tlodsb/n/t"
"stosb/n/t"
"testb %%al,%%al/n/t"
"jne 1b"
: "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
: "0" (src), "1" (dest), "2" (0), "3" (0xffffffffu):"memory");
return dest;
}

static inline char * strncat(char * dest,const char * src,size_t count)
{
int d0, d1, d2, d3;
__asm__ __volatile__(
"repne/n/t"
"scasb/n/t"
"decl %1/n/t"
"movl %8,%3/n"
"1:/tdecl %3/n/t"
"js 2f/n/t"
"lodsb/n/t"
"stosb/n/t"
"testb %%al,%%al/n/t"
"jne 1b/n"
"2:/txorl %2,%2/n/t"
"stosb"
: "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
: "0" (src),"1" (dest),"2" (0),"3" (0xffffffffu), "g" (count)
: "memory");
return dest;
}

#define __HAVE_ARCH_STRCMP
static inline int strcmp(const char * cs,const char * ct)
{
int d0, d1;
register int __res;
__asm__ __volatile__(
"1:/tlodsb/n/t"
"scasb/n/t"
"jne 2f/n/t"
"testb %%al,%%al/n/t"
"jne 1b/n/t"
"xorl %%eax,%%eax/n/t"
"jmp 3f/n"
"2:/tsbbl %%eax,%%eax/n/t"
"orb $1,%%al/n"
"3:"
:"=a" (__res), "=&S" (d0), "=&D" (d1)
:"1" (cs),"2" (ct)
:"memory");
return __res;
}

#define __HAVE_ARCH_STRNCMP
static inline int strncmp(const char * cs,const char * ct,size_t count)
{
register int __res;
int d0, d1, d2;
__asm__ __volatile__(
"1:/tdecl %3/n/t"
"js 2f/n/t"
"lodsb/n/t"
"scasb/n/t"
"jne 3f/n/t"
"testb %%al,%%al/n/t"
"jne 1b/n"
"2:/txorl %%eax,%%eax/n/t"
"jmp 4f/n"
"3:/tsbbl %%eax,%%eax/n/t"
"orb $1,%%al/n"
"4:"
:"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
:"1" (cs),"2" (ct),"3" (count)
:"memory");
return __res;
}

#define __HAVE_ARCH_STRCHR
static inline char * strchr(const char * s, int c)
{
int d0;
register char * __res;
__asm__ __volatile__(
"movb %%al,%%ah/n"
"1:/tlodsb/n/t"
"cmpb %%ah,%%al/n/t"
"je 2f/n/t"
"testb %%al,%%al/n/t"
"jne 1b/n/t"
"movl $1,%1/n"
"2:/tmovl %1,%0/n/t"
"decl %0"
:"=a" (__res), "=&S" (d0)
:"1" (s),"0" (c)
:"memory");
return __res;
}

#define __HAVE_ARCH_STRRCHR
static inline char * strrchr(const char * s, int c)
{
int d0, d1;
register char * __res;
__asm__ __volatile__(
"movb %%al,%%ah/n"
"1:/tlodsb/n/t"
"cmpb %%ah,%%al/n/t"
"jne 2f/n/t"
"leal -1(%%esi),%0/n"
"2:/ttestb %%al,%%al/n/t"
"jne 1b"
:"=g" (__res), "=&S" (d0), "=&a" (d1)
:"0" (0),"1" (s),"2" (c)
:"memory");
return __res;
}

#define __HAVE_ARCH_STRLEN
static inline size_t strlen(const char * s)
{
int d0;
register int __res;
__asm__ __volatile__(
"repne/n/t"
"scasb/n/t"
"notl %0/n/t"
"decl %0"
:"=c" (__res), "=&D" (d0)
:"1" (s),"a" (0), "0" (0xffffffffu)
:"memory");
return __res;
}

static __always_inline void * __memcpy(void * to, const void * from, size_t n)
{
int d0, d1, d2;
__asm__ __volatile__(
"rep ; movsl/n/t"
"movl %4,%%ecx/n/t"
"andl $3,%%ecx/n/t"
#if 1/* want to pay 2 byte penalty for a chance to skip microcoded rep? */
"jz 1f/n/t"
#endif
"rep ; movsb/n/t"
"1:"
: "=&c" (d0), "=&D" (d1), "=&S" (d2)
: "0" (n/4), "g" (n), "1" ((long) to), "2" ((long) from)
: "memory");
return (to);
}

/*
* This looks ugly, but the compiler can optimize it totally,
* as the count is constant.
*/
static __always_inline void * __constant_memcpy(void * to, const void * from, size_t n)
{
long esi, edi;
if (!n) return to;
#if 1/* want to do small copies with non-string ops? */
switch (n) {
case 1: *(char*)to = *(char*)from; return to;
case 2: *(short*)to = *(short*)from; return to;
case 4: *(int*)to = *(int*)from; return to;
#if 1/* including those doable with two moves? */
case 3: *(short*)to = *(short*)from;
*((char*)to+2) = *((char*)from+2); return to;
case 5: *(int*)to = *(int*)from;
*((char*)to+4) = *((char*)from+4); return to;
case 6: *(int*)to = *(int*)from;
*((short*)to+2) = *((short*)from+2); return to;
case 8: *(int*)to = *(int*)from;
*((int*)to+1) = *((int*)from+1); return to;
#endif
}
#endif
esi = (long) from;
edi = (long) to;
if (n >= 5*4) {
/* large block: use rep prefix */
int ecx;
__asm__ __volatile__(
"rep ; movsl"
: "=&c" (ecx), "=&D" (edi), "=&S" (esi)
: "0" (n/4), "1" (edi),"2" (esi)
: "memory"
);
} else {
/* small block: don't clobber ecx + smaller code */
if (n >= 4*4) __asm__ __volatile__("movsl"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
if (n >= 3*4) __asm__ __volatile__("movsl"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
if (n >= 2*4) __asm__ __volatile__("movsl"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
if (n >= 1*4) __asm__ __volatile__("movsl"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
}
switch (n % 4) {
/* tail */
case 0: return to;
case 1: __asm__ __volatile__("movsb"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
return to;
case 2: __asm__ __volatile__("movsw"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
return to;
default: __asm__ __volatile__("movsw/n/tmovsb"
:"=&D"(edi),"=&S"(esi):"0"(edi),"1"(esi):"memory");
return to;
}
}