#include <stdio.h>#include <stdlib.h>#include <assert.h>int my_strlen(char *s){    assert(s!=NULL);    int count=0;    while(*s!=‘\0‘)    {         s++;         count++;    }    return count;}char *my_strcpy(char *s1,const char *s2){    assert(s1!=NULL);    assert(s2!=NULL);    char *res=s1;    while(*s2!=‘\0‘)    {        *s1=*s2;        s1++;//s1,s2均指向未赋值的下一个字节        s2++;    }    *s1=‘\0‘;    return res;}char *my_strncpy(char *s1,const char *s2,int n){    assert(s1!=NULL);    assert(s2!=NULL);    char *res=s1;    while(*s2!=‘\0‘&&n)    {        *s1=*s2;        s1++;        s2++;        n--;    }    *s1=‘\0‘;    return res;}char *my_strchr(char *str,int c){    assert(str!=NULL);    while(*str!=‘\0‘)    {        if(*str==(char)c)            return str;        else            str++;    }    return NULL;}char *my_strstr(const char *str,char *sub){   assert(str!=NULL&&sub!=NULL);   char *s=str;   char *t=sub;   int len=0;   for(;*s!=‘\0‘;s++)   {      while(*t!=‘\0‘&&*s==*t)      {          s++;          t++;          len++;      }        if(*t==‘\0‘)            return s-len;   }   return NULL;}char *my_strcat(char *s1,const char *s2){    assert(s1!=NULL);    assert(s2!=NULL);    char *res=s1;    while(*s1!=‘\0‘)        s1++;    while(*s2!=‘\0‘)    {        *s1=*s2;        s1++;        s2++;    }    *s1=‘\0‘;    return res;}int my_strcmp(const char *s1,const char *s2){    assert(s1!=NULL);    assert(s2!=NULL);    while(*s1!=‘\0‘&&*s2!=‘\0‘&&*s1==*s2)    {        s1++;        s2++;    }    return *s1-*s2;}char *my_strdup(char *s){    assert(s!=NULL);    int len=0;    char *dup=(char*)malloc(sizeof(char)*(len+1));    if(NULL==dup)        return NULL;    while(*s!=‘\0‘)    {        *dup=*s;        dup++;        s++;        len++;    }    *dup=‘\0‘;    return dup-len;}void *my_memset(void* buffer,int c,int n){   assert(buffer!=NULL);   char *p=(char*)buffer;   while(n--)   {        *p=(char)c;        p++;   }   return  buffer;}//拷贝内存块，不考虑内存重叠void *my_memcpy(void *to,const void *from,int n){   assert((to!=NULL)&&(from!=NULL));   char *res=(char *)to;   char *t=(char*)to;   char *f=(char*)from;   assert((t<f)||(t>f-n+1));   while(n--)   {       *t=*f;       t++;       f++;   }   return res;}void *my_memmove(void *to,void *from,int count){   assert((to!=NULL)&&(from!=NULL));   char *res=(char*)to;   char *des=(char*)to;   char *src=http://www.mamicode.com/(char*)from;"strlen";    int len=my_strlen(str);    printf("my_strlen:%d\n",len);    //my_strcpy  my_strncpy    char s1_cpy[10]="str";    char s2_cpy[10]="cpy";    char *s_cpy=my_strcpy(s1_cpy,s2_cpy);    printf("%s\n",s_cpy);    //my_strncpy    char s1_ncpy[20]="strncpy";    char s2_ncpy[10]="strn";    char *s_ncpy=my_strncpy(s1_ncpy,s2_ncpy,3);    printf("%s\n",s_ncpy);    //my_strcat    char s1_cat[20]="strcat";    char s2_cat[10]="after";    char *s_cat=my_strcat(s1_cat,s2_cat);    printf("%s\n",s_cat);    //my_strcmp    char s1_cmp[10]="cmp1";    char s2_cmp[10]="cmp2";    printf("%d\n",my_strcmp(s1_cmp,s2_cmp));    //my_strchr    char s_chr[10]="strchr";    char *p_chr=my_strchr(s_chr,‘t‘);    if(NULL!=p_chr)    printf("%s\n",p_chr);    else    printf("don‘t have this character.\n");    //my_strdup    char s_d[10]="strdup";    char *s_dup=my_strdup(s_d);    printf("%s\n",s_dup);    free(s_dup);    //my_strstr    char s_str[20]="abcdrgrkj";    char t_str[10]="bcd";    printf("%s\n",my_strstr(s_str,t_str));    //my_memset    char s_mem[10]="hello";    char *p_mem=my_memset(s_mem,‘*‘,strlen(s_mem));    char s_mem1[10]="hello";    char *p_mem1=my_memset(s_mem1,‘*‘,sizeof(s_mem1));    printf("%s\n",p_mem);    printf("%s\n",p_mem1);    //my_memcpy    char s_memcpy[10]="abcd";    char *p=my_memcpy(s_memcpy,s_memcpy+2,2);//未发生内存重叠    printf("%s\n",p);    char s1_memcpy[10]="abcd";    char *p1=my_memcpy(s1_memcpy+2,s1_memcpy,3);//未处理内存重叠，输出aba    printf("%s\n",p1);    //my_memmove    char s_move[10]="abcd";    char *p_m=my_memmove(s_move+2,s_move,3);//正确处理内存重叠，输出abc    printf("%s\n",p_m);    return 0;}