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）

 1 // TestGetFileSize.cpp : Defines the entry point for the console application.
 2 //
 3 
 4 #include "stdafx.h"
 5 #include <iostream>
 6 #include <windows.h>
 7 #include <io.h>
 8 #include <sys\stat.h>
 9 
10 using namespace std;
11 
12 size_t GetFileSize1(LPCTSTR lpszFileName)
13 {
14    size_t nResult = 0;
15    HANDLE handle = CreateFile(lpszFileName, FILE_READ_EA, FILE_SHARE_READ, 0, OPEN_EXISTING, 0, 0);
16    if (handle != INVALID_HANDLE_VALUE)
17    {
18        nResult = GetFileSize(handle, NULL);
19        CloseHandle(handle);
20    }
21    return nResult;
22 }
23 
24 size_t GetFileSize2(LPCTSTR lpszFileName)
25 {
26    size_t nResult = 0;
27    WIN32_FIND_DATA fileInfo; 
28    HANDLE hFind; 
29    hFind = FindFirstFile(lpszFileName, &fileInfo); 
30    if(hFind != INVALID_HANDLE_VALUE) 
31        nResult = fileInfo.nFileSizeLow; 
32    FindClose(hFind); 
33    return nResult;
34 }
35 
36 size_t GetFileSize3(LPCTSTR lpszFileName)
37 {
38    size_t nResult = 0;
39    FILE* file = fopen(lpszFileName, "r");
40    if (file)
41    {
42        nResult = filelength(fileno(file));
43        fclose(file);
44    }
45    return nResult;
46 }
47 
48 size_t GetFileSize4(LPCTSTR lpszFileName)
49 {
50    size_t nResult = 0;
51    struct _stat info;
52    _stat(lpszFileName, &info);
53    nResult = info.st_size;
54    return nResult;
55 }
56 
57 DWORD Test(size_t (*pFunc)(LPCTSTR), LPCTSTR lpszFileName)
58 {
59    DWORD dwResult = 0;
60    size_t nFileSize = 0;
61    DWORD tick = GetTickCount();
62    for (int i=0; i<10000; i++)
63    {
64        nFileSize = pFunc(lpszFileName);
65 //     cout<<"FileSize = "<<nFileSize<<endl;
66    }
67    dwResult = GetTickCount() - tick;
68    cout<<"Cost: "<<dwResult<<endl;
69    return dwResult;
70 }
71 
72 
73 int main(int argc, char* argv[])
74 {
75    char *szFileName = "G:\\1.txt";
76    DWORD dwCost[4] = {0};
77    
78    dwCost[0] = Test(GetFileSize1, szFileName);
79    system("pause");
80    
81    dwCost[1] = Test(GetFileSize2, szFileName);
82    system("pause");
83    
84    dwCost[2] = Test(GetFileSize3, szFileName);
85    system("pause");
86    
87    dwCost[3] = Test(GetFileSize4, szFileName);
88    system("pause");
89    
90    return 0;
91 }

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。