C语言字符串的相关操作（连接，比较等）

#include<stdio.h>
#include<stdlib.h>
#define MaxSize 100
typedef struct String{
	char ch[MaxSize];
	int len;
}String;


int getStrLen(String *S){//获取字符串的长度
  int i=0;
  while(S->ch[i]!='\0'){
   i++;
  }
  if(i>=MaxSize){
    return -1;
  }else{
    S->len=i;
	return i;
  }
}

//初始化字符串
void initString(String *S){
  gets(S->ch);
  S->len=getStrLen(S);
}
//连接字符串
int StrCat(String *S,String *T){
	int i;
	int flag;
	if(S->len+T->len<=MaxSize)
	{
	for(i=S->len;i<S->len+T->len;i++){
			S->ch[i]=T->ch[i-S->len];
	}
	S->ch[i]='\0';
	S->len+=T->len;
	flag=1;
	return flag;
	}else if(S->len<MaxSize){
		for(i=S->len;i<MaxSize;i++){
			S->ch[i]=T->ch[i-S->len];
		}
		S->len=MaxSize;
		flag=1;
		return flag;
	}else{
     flag=-1;
    return flag;
	}
}
//字符串的赋值
void StrAsign(String *S,char a[]){
int i=0;
while(a[i]!='\0'){
	S->ch[i]=a[i];
	i++;
}
//这里出现了bug
S->ch[i]='\0';
S->len=getStrLen(S);
}
//字符串的删除
void strDelete(String *S,int pos,int offset){//定义删除字符串的开始位置和偏移
	if(pos+offset-1>S->len){
		printf("所要删除的子串超界");
	}
	else{
		for(int k=pos;k<S->len;k++){
			S->ch[k]=S->ch[k+offset];
		}		
		S->len-=offset;
		S->ch[S->len]='\0';
	}
}
//串的比较
int StrCompare(String *s1,String *s2){
	int i=0,flag=0;
	while(s1->ch[i]!='\0'&& s2->ch[i]!='\0'){
		if(s1->ch[i]!=s2->ch[i]){
			flag=1;
			break;
		}
		else{
		  i++;
		}
	}
	if(flag==0 && s1->len==s2->len){
		return 0;
	}else{
		return s1->ch[i]-s2->ch[i];
	}
}

void main(){
	system("color 07");
String s1,s2,s3;
String *S3=&s3;
char a[]="this is string test";
StrAsign(S3,a);
printf("字符串赋值后的值为%s\n",S3->ch);
strDelete(S3,0,1);
printf("字符串删除后的值为%s\n",S3->ch);
String *S1=&s1;
String *S2=&s2;
initString(S1);
//printf("\n");
initString(S2);
if(StrCompare(S1,S2)==0){
    printf("字符串相等");
}else{
   printf("字符串不相等,相差%d",StrCompare(S1,S2));
}

if(StrCat(S1,S2)!=-1){
    printf("字符串的连接成功,连接后的字符串为%s",S1->ch);
}else{
	printf("字符串的连接失败");
}
}