//
// main.cpp
// AUTO_PRO
//
// Created by yanzhengqing on 12-12-11.
// Copyright (c) 2012年 yanzhengqing. All rights reserved.
//
#include <iostream>
using namespace std;
/***
*int strncmp(first, last, count) - compare first count chars of strings
*
*Purpose:
* Compares two strings for lexical order. The comparison stops
* after: (1) a difference between the strings is found, (2) the end
* of the strings is reached, or (3) count characters have been
* compared.
*
*Entry:
* char *first, *last - strings to compare
* unsigned count - maximum number of characters to compare
*
*Exit:
* returns <0 if first < last
* returns 0 if first == last
* returns >0 if first > last
*
*Exceptions:
*
*******************************************************************************/
/////////////////////////////////////////////////////////////////////////////////
/*說明:
1. __cdecl 是C Declaration的縮寫(declaration,聲明),表示C語言默認的函數調用方法:所有參數從右到左依次入棧,這些參數由調用者清除,稱爲手動清棧。被調用函數不會要求調用者傳遞多少參數,調用者傳遞過多或者過少的參數,甚至完全不同的參數都不會產生編譯階段的錯誤。
2. 基於字典順序比較兩個字符串,最多比較n個字節
3. 按照ANSI(American National Standards Institute)標準,不能對void指針進行算法操作,即不能對void指針進行如p++的操作,所以需要轉換爲具體的類型指針來操作,例如char *。(引用網友的結論)
4. size_t 類型定義在cstddef頭文件中,該文件是C標準庫的頭文件stddef.h的C++版。它是一個與機器相關的unsigned類型,其大小足以保證存儲內存中對象的大小。
*/
int __cdecl strncmp (
const char * first,
const char * last,
size_t count
)
{
if (!count)
return(0);
while (--count && *first && *first == *last)
{
first++;
last++;
}
return( *(unsignedchar *)first - *(unsignedchar *)last );
}
int main()
{
int p = 0;
const char src[50] ="blog.csdn.con";
constchar brc[50] ="blog.csdn.net/barry_yan";
cout<<src<<endl;
cout<<brc<<endl;
p =strncmp(src,brc,strlen(src)+1);
cout<<p<<endl;
return 0;
}