strcpy函數和string類的實現

標籤：strcpy   c++   

1 strcpy函數實現

void* memcpy1(void *dst,const void *src,int count){assert(dst != NULL && src!= NULL && count>=0);void *temp = dst;char *pdst = (char*)dst;char *psrc = (char*)src;if(pdst>=psrc && pdst <= psrc+count-1){pdst = pdst + count -1;psrc = psrc + count -1;while (count--)*pdst-- = *psrc--;}else{while(count--)*pdst++ = *psrc++;}return temp;}char* strcpy1(char *dst,const char *src){assert(dst != NULL && src!= NULL);char *temp = dst;memcpy1(dst,src,strlen(src)+1);return temp;}

2 string 類的部分實現

class MyString{public:friend ostream& operator<<(ostream&,const MyString&);MyString(const char *str = NULL){if(NULL == str)m_data = 0;else{m_data = new char[strlen(str)+1];strcpy(m_data,str);}}MyString(const MyString & string){if(string.m_data == 0 || string.m_data == NULL)m_data = 0;else{m_data = new char[strlen(string.m_data)+1];strcpy(m_data,string.m_data);}}MyString& operator=(const MyString &string){if(this != &string){char *temp = m_data;if(string.m_data==0 || string.m_data == NULL)m_data = 0;else{m_data = new char[strlen(string.m_data)+1];strcpy(m_data,string.m_data);}delete []temp;}return *this;}private:char *m_data;};

strcpy函數和string類的實現