初试断言

#include <stdio.h>
#include <stdlib.h>

//#define NDEBUG	//禁用NDBUG
#include <assert.h>
typedef unsigned char byte;

#define DEBUG	//自定义的断言宏


/* memcpy ─── 拷贝不重叠的内存块*/
void* memcpy(void* pvTo, void* pvFrom, size_t size)
{
	byte* pbTo = (byte*)pvTo;
	byte* pbFrom = (byte*)pvFrom;
	if(pvTo == NULL || pvFrom == NULL)
	{
		fprintf(stderr, "Bad args in memcpy\n");
		abort();
	}
	while(size-->0)
		*pbTo++ = *pbFrom++;
	return(pvTo);
}



void* memcpy2(void* pvTo, void* pvFrom, size_t size)
{
	byte* pbTo = (byte*)pvTo;
	byte* pbFrom = (byte*)pvFrom;
#ifdef DEBUG
	if(pvTo == NULL || pvFrom == NULL)
	{
		fprintf(stderr, "Bad args in memcpy\n");
		abort();
	}
#endif
	while(size-->0)
		*pbTo++ = *pbFrom++;
	return(pvTo);
}


void* memcpy3(void* pvTo, void* pvFrom, size_t size)
{
	byte* pbTo = (byte*)pvTo;
	byte* pbFrom = (byte*)pvFrom;
	assert(NULL != pvTo && NULL != pvFrom );
	while(size-->0)
		*pbTo++ = *pbFrom++;
	return(pvTo);
}



#ifdef DEBUG
void _Assert(char* , unsigned); /* 原型*/
#define ASSERT(f) \
	if(f) \
	NULL; \
	else \
	_Assert(__FILE__ , __LINE__)//这个宏定义不能放在表达式当中
#else
#define ASSERT(f) NULL
#endif

void _Assert(char* strFile, unsigned uLine)
{
	fflush(stdout);
	fprintf(stderr, "\nAssertion failed: %s, line %u\n",strFile, uLine);
	fflush(stderr);
	abort();
}

void* memcpy4(void* pvTo, void* pvFrom, size_t size)
{
	byte* pbTo = (byte*)pvTo;
	byte* pbFrom = (byte*)pvFrom;
	ASSERT(NULL != pvTo && NULL != pvFrom );
	while(size-->0)
		*pbTo++ = *pbFrom++;
	return(pvTo);
}


/* memcpy ─── 拷贝不重叠的内存块*/
void* memcpy5(void* pvTo, void* pvFrom, size_t size)
{
	byte* pbTo = (byte*)pvTo;
	byte* pbFrom = (byte*)pvFrom;
	ASSERT(NULL != pvTo && NULL != pvFrom );	//要使用断言对函数参数进行确认
	ASSERT(pbFrom+size <= pbTo || pbTo+size <= pbFrom);	/* 内存块重叠吗？如果重叠，就使用memmove */
	while(size-->0)
		*pbTo++ = *pbFrom++;
	return(pvTo);
}


const int len = 20;

int main()
{
	char *pchFrom = new char[len];
	pchFrom[0] = 's';
	pchFrom[1] = '\0';
	char *pchTo = NULL;
	//memcpy3(pchTo, pchFrom,len);
	//memcpy4(pchTo, pchFrom,len);
	memcpy5(pchTo, pchFrom,len);
	return 0;
}