一个关于 strstr()的理解问题
如下,我想该怎样去阅读类似__volatile__的代码,谢谢:***************************
char * strstr(const char * cs,const char * ct)
{
int d0, d1;
register char * __res;
__asm__ __volatile__(
"movl %6,%%edi\n\t"
"repne\n\t"
"scasb\n\t"
"notl %%ecx\n\t"
"decl %%ecx\n\t" /* NOTE! This also sets Z if searchstring='' */
"movl %%ecx,%%edx\n"
"1:\tmovl %6,%%edi\n\t"
"movl %%esi,%%eax\n\t"
"movl %%edx,%%ecx\n\t"
"repe\n\t"
"cmpsb\n\t"
"je 2f\n\t" /* also works for empty string, see above */
"xchgl %%eax,%%esi\n\t"
"incl %%esi\n\t"
"cmpb $0,-1(%%eax)\n\t"
"jne 1b\n\t"
"xorl %%eax,%%eax\n\t"
"2:"
:"=a" (__res), "=&c" (d0), "=&S" (d1)
:"0" (0), "1" (0xffffffff), "2" (cs), "g" (ct)
:"dx", "di");
return __res;
} 给翻译以下
=============
输入参数部分
=============
eax = 0
ecx = 0xffffffff
esi = cs
=============
主体
=============
movl ct, %edi
repne
scasb
notl %ecx
decl %ecx
movl %ecx,%edx
again:
movl ct,%edi
movl %esi,%eax
movl %edx,%ecx
repe
cmpsb
je exit
xchgl %eax,%esi
incl %esi
cmpb $0, -1(%eax)
jne again
xorl %eax,%eax
exit:
==============
输出参数
==============
__res = eax 非常感谢!!!
哪有相关的电子入门/讲解资料可参考?
这个有人说是用Mips的compiler做的.
给翻译以下
=============
输入参数部分
=============
eax = 0
ecx = 0xffffffff
esi = cs <======这个是做什么???
=============
主体
=============
movl ct, %edi
repne
scasb
notl %ecx
decl %ecx
movl %ecx,%edx
again:
movl ct,%edi
movl %esi,%eax
movl %edx,%ecx
repe
cmpsb
je exit
xchgl %eax,%esi
incl %esi
cmpb $0, -1(%eax)
jne again
xorl %eax,%eax
exit:
==============
输出参数
==============
__res = eax
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