实现C语言常用字符串库函数

size_t strlen ( const char * str );

int my_strlen(char *str)
{
	char* ch=str;
	int count=0;
	while(*ch!='\0')
	{
		count++;
		ch++;
	}
	return count;
}

int my_strlen(const char *str)
{
	char* ch=str;
	int count=0;
	while(*ch!='\0')
	{
		count++;
		ch++;
	}
	return count;
}

char * strcpy ( char * destination, const char * source );

void my_strcpy(char* dest,const char *src)
{
	char * ch=src;
	while(*ch!='\0')
	{
		*dest=*ch;
		dest++;
		ch++;
	}
	*dest='\0';
}

char * strcat ( char * destination, const char * source );

void my_strcat(char* dest,const char *src)
{
	char * ch=dest;
	while(*ch!='\0')ch++;
	while(*src!='\0')
	{
		*ch=*src;
		ch++;
		src++;
	}
	*ch='\0';
}

int strcmp ( const char * str1, const char * str2 );

int my_strcmp(const char* str1,const char *str2)
{
	assert(str1);
	assert(str2);
	char * s1=str1;
	char * s2=str2;
	while(*s1==*s2)
	{
		if(*s1=='\0')
		{
			return 0;
		}
		s1++;
		s2++;
	}
	if(*s1>*s2)
	{
		return 1;
	}
	else
	{
		return -1;
	}
}