[C++知识库]C语言实现trlen |strcpy |stract |strcmp

#include?<stdio.h>??????????????????????????????????????????????????????????????

#include?<string.h>?

#include?<assert.h>

size_t?str_len(const?char*?str)

{

????assert(NULL?!=?str);

????const?char*?tmp?=?str;

????while(*tmp)?tmp++;

????return?tmp-str;

}

char*?str_cpy(char*?dest,const?char*?src)

{

????assert(NULL?!=?dest??&&?NULL?!=?src);

????char*?tmp?=?dest;

????while(*tmp++?=?*src++);

????return?dest;

}

char*?str_cat(char*?dest,const?char*?src)

{

????assert(NULL?!=?dest??&&?NULL?!=?src);

????char*?tmp=dest;

????while(*tmp)?tmp++;

????while(*tmp++?=?*src++);

????return?dest;

}

int?str_cmp(const?char*?s1,const?char*?s2)

{

????assert(NULL?!=?s1??&&?NULL?!=?s2);

????while(*s1?&&?*s1?==?*s2)?s1++,s2++;

????return?*s1-*s2;

}

int?main(int?argc,const?char*?argv[])

{

????char?str[256]="hehe";

????printf("%d\n",str_len(str));

????printf("%s\n",str_cpy(str,"abcdef"));

????printf("%s\n",str_cat(str,"qqq"));

????printf("%d\n",str_cmp("abd","abc"));

}?