一、C语言str族函数strchr、strstr实现

1.C语言strchr()函数实现算法

char* StringChr(char *pSource, char c)
{
	while (*pSource)
	{
		if (*pSource == c)
			return pSource;
		++pSource;
	}
	return NULL;
}

2.C语言strstr()函数实现算法

char* StringSubStr(char *pSource, char* subStr)
{
	char* pBegin = subStr;
	char* pS = pSource;
	while (*pSource)
	{
		if (*pSource == *pBegin)
		{
			pS = pSource;
			while (*subStr&&*pSource==*subStr)
			{
				++subStr;
				++pSource;
			}
			if (*subStr == '\0')
				return pS;
			pSource = pS;
			subStr = pBegin;
		}
		++pSource;
	}
	return NULL;
}

二、C语言内存族函数memset、memcpy实现

1.C语言memset()函数实现算法

void Memset(void* dest, char c, int nCount)
{
	char* p = (char*)dest;
	int i = 0;
	while (i < nCount)
		p[i++] = c;
}

2.C语言memcpy()函数实现算法

void MemCpy(void* pDest, void* pSource, int nCount)
{
	char* pDst = (char*)pDest;
	char* pSrc = (char*)pSource;
	int i = 0;
	while (i++<nCount)
		*pDst++ = *pSrc++;
}