字符串函数实现

字符串函数实现

#include <iostream>
using namespace std;
#define LEN 255
char *Mystrcpy(char *to, const char *from);
size_t Mystrlen(const char *str);
char *Mystrcat(char *str1, const char *str2);
char *Mymemset(char *buffer, int ch, size_t count);
int Mystrcmp(const char * str1, const char * str2);
char * Mystrstr(char * str1, const char * str2);
int main()
{
	char p[LEN] = "ee";
	char pp[LEN] = "aaa";
	Mystrcpy(p, pp);
	cout << p << endl;
	int size = Mystrlen("asd");
	cout << size << endl;
	Mystrcat(p, pp);
	cout << p << endl;
	char ppp[LEN] = "aaaaa";
	while (Mystrcmp(p, ppp) == 0)
	{
		cout << "完全相同" << endl;
		break;
	}
	char pppp[LEN] = "vvvvaaaaaaqqqqqqqqq";
	char* pch = Mystrstr(pppp, ppp);
	cout << pch << endl;
	return 0;
}
size_t Mystrlen(const char *str)
{
	int length = 0;
	for (int i = 0; *(str + i) != '\0'; ++i)
	{
		length++;
	}
	return length;
}
char *Mystrcpy(char *to, const char *from)
{
	if (*from == '\0' || *to == '\0')
	{
		return NULL;
	}
	else
	{
		int length = Mystrlen(from);//调用Mystrlen
		Mymemset(to, 0, length + 1);
		while (*from != NULL)
		{
			*to = *from;
			to++;
			from++;
		}
		return to;
	}
}
char *Mystrcat(char *str1, const char *str2)
{
	int length = Mystrlen(str1);
	str1 += length;
	while (*str2 != NULL)
	{
		*str1 = *str2;
		str1++;
		str2++;
	}
	return str1;
}
char *Mymemset(char *buffer, int ch, size_t count)
{

	for (unsigned int i = 0; i < count; ++i)
	{
		*(buffer + i) = ch;
	}
	return buffer;
}
int Mystrcmp(const char * str1, const char * str2)
{
	if (*str1++ == *str2++)
	{
		return 0;
	}
	else if (*str1++ > *str2++)
	{
		return 1;
	}
	else
	{
		return -1;
	}
}
char * Mystrstr(char * str1, const char * str2)
{
	for (int i = 0; *(str1 + i) != NULL; ++i)
	{
		for (int j = 0, k = i; *(str1 + k++) == *(str2 + j++);)
		{
			if (*(str2 + j) == '\0')
			{
				return (str1 + k);
			}
		}
	}

	return NULL;
}