strcpy函数的实现

/*
my strcpy

@author arhaiyun

*/

#include<assert.h>
#include<string.h>

char* m_strcpy(char* dst, char* src)
{
	//[1].Check to make sure it is valid
	assert((dst != NULL) && (src != NULL));
	
	char* ret = dst;

	int length = strlen(src) + 1;
	
	//[2].Make sure memory is not repeated
	if(dst <= src || dst >= (src + length))
	{
		//[3].Copy '\0' in the end
		while(length--)
		{
			*dst++ = *src++;
		}
	}
	else
	{
		dst = dst + length - 1;
		src = src + length - 1;
		while(length--)	
		{
			*dst-- = *src--;
		}
	}
	
	//[4].return dst
	return ret;
}