编写测试：VC下获取文件大小的4种方法

代码参考自lailx的博客：获取文件大小的4种方法（http://www.cnblogs.com/lailx/archive/2011/11/20/2256550.html）

 

// TestGetFileSize.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <io.h>
#include <sys\stat.h>

using namespace std;

size_t GetFileSize1(LPCTSTR lpszFileName)
{
   size_t nResult = 0;
   HANDLE handle = CreateFile(lpszFileName, FILE_READ_EA, FILE_SHARE_READ, 0, OPEN_EXISTING, 0, 0);
   if (handle != INVALID_HANDLE_VALUE)
   {
       nResult = GetFileSize(handle, NULL);
       CloseHandle(handle);
   }
   return nResult;
}

size_t GetFileSize2(LPCTSTR lpszFileName)
{
   size_t nResult = 0;
   WIN32_FIND_DATA fileInfo; 
   HANDLE hFind; 
   hFind = FindFirstFile(lpszFileName, &fileInfo); 
   if(hFind != INVALID_HANDLE_VALUE) 
       nResult = fileInfo.nFileSizeLow; 
   FindClose(hFind); 
   return nResult;
}

size_t GetFileSize3(LPCTSTR lpszFileName)
{
   size_t nResult = 0;
   FILE* file = fopen(lpszFileName, "r");
   if (file)
   {
       nResult = filelength(fileno(file));
       fclose(file);
   }
   return nResult;
}

size_t GetFileSize4(LPCTSTR lpszFileName)
{
   size_t nResult = 0;
   struct _stat info;
   _stat(lpszFileName, &info);
   nResult = info.st_size;
   return nResult;
}

DWORD Test(size_t (*pFunc)(LPCTSTR), LPCTSTR lpszFileName)
{
   DWORD dwResult = 0;
   size_t nFileSize = 0;
   DWORD tick = GetTickCount();
   for (int i=0; i<10000; i++)
   {
       nFileSize = pFunc(lpszFileName);
//     cout<<"FileSize = "<<nFileSize<<endl;
   }
   dwResult = GetTickCount() - tick;
   cout<<"Cost: "<<dwResult<<endl;
   return dwResult;
}


int main(int argc, char* argv[])
{
   char *szFileName = "G:\\1.txt";
   DWORD dwCost[4] = {0};
   
   dwCost[0] = Test(GetFileSize1, szFileName);
   system("pause");
   
   dwCost[1] = Test(GetFileSize2, szFileName);
   system("pause");
   
   dwCost[2] = Test(GetFileSize3, szFileName);
   system("pause");
   
   dwCost[3] = Test(GetFileSize4, szFileName);
   system("pause");
   
   return 0;
}

测试结果：

 

当目标文件正在被写入的时候，体积逐渐增大，但测试发现第GetFileSize2()、GetFileSize4()返回的文件大小是固定不变的，因此在需要监视文件大小时，这两种方法不可取。