C语言字符串函数实现源码汇总.doc

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1、C语言字符串函数实现源码汇总2008年05月18日星期日16:541/*2  *  linux/lib/string.c3  *4  *  Copyright(C)1991,1992  LinusTorvalds5  */67/*8  *stupidlibraryroutines..Theoptimizedversionsshouldgenerallybefound9  *asinlinecodein10  *11  *Thesearebuggyaswell..12  */13  14#

2、include1516char*___strtok=NULL;1718char*strcpy(char*dest,constchar*src)19{20         char*tmp=dest;2122         while((*dest++=*src++)!='')23 ;24         returntmp;25}2627char*strncpy(char*dest,constchar*src,size_tcount)28{29         char*tmp=des

3、t;3031         while(count--&&(*dest++=*src++)!='')32                 /*nothing*/;3334         returntmp;35}3637char*strcat(char*dest,constchar*src)38{39         char*tmp=dest;4041         while(*dest)42                 dest++;43         while((*dest++=*src++)!

4、='')44                 ;4546         returntmp;47}4849char*strncat(char*dest,constchar*src,size_tcount)50{51         char*tmp=dest;5253         if(count){54                 while(*dest)55                         dest++;56                 while((*dest++=*src++))

5、{57                         if(--count==0)58                                 break;59                 }60         }6162         returntmp;63}6465intstrcmp(constchar*cs,constchar*ct)66{67         registersignedchar__res;6869         while(1){70                 if(

6、(__res=*cs-*ct++)!=0

7、

8、!*cs++)71                         break;72         }7374         return__res;75}7677intstrncmp(constchar*cs,constchar*ct,size_tcount)78{79         registersignedchar__res=0;8081         while(count){82                 if((__res=*cs-*ct++)!=0

9、

10、

11、!*cs++)83                         break;84                 count--;85         }8687         return__res;88}8990char*strchr(constchar*s,charc)91{92         for(;*s!=c;++s)93                 if(*s=='')94                         returnNULL;95         return(char

12、*)s;96}9798size_tstrlen(constchar*s)99{100         constchar*sc;101102         for(sc=s;*sc!='';++sc)103                 /*nothing*/;104         returnsc-s;1