關于宏MAX_PATH與文件名長度的關系

目的：測試MAX_PATH路徑與文件名的關系。

結論：MAX_PATH代表從盤符開始到文件名結尾的C字符串長度（長度+1）的最大長度。也就是假設C:\a.txt共8個字符，長度為9，MAX_PATH通常為260，其中這個文件全名的長度不能大于260。

測試代碼：

#include "stdafx.h"
#include <atlbase.h>
#include <windows.h>
#include <atlfile.h>
#include <atlstr.h>
#include <iostream>
#include <string>

BOOL IsFileExist( LPCTSTR lpszFileName )
{
    DWORD dwAttr = ::GetFileAttributes( lpszFileName );
    if ( dwAttr == 0xFFFFFFFF )
    {
        return FALSE;
    }
    if ( ( dwAttr & FILE_ATTRIBUTE_DIRECTORY ) > 0 )
    {
        return FALSE;
    }
    return TRUE;
}

BOOL DeleteFiles( LPCTSTR lpszPath )
{
    TCHAR szFrom[_MAX_PATH+1] = {_T( '\0' )};
    lstrcpy( szFrom , lpszPath );
    SHFILEOPSTRUCT shf;
    memset( &shf, 0, sizeof( SHFILEOPSTRUCT ) );
    shf.hwnd = NULL;
    shf.pFrom = szFrom;
    shf.wFunc = FO_DELETE;
    shf.fFlags = FOF_NOCONFIRMMKDIR | FOF_NOCONFIRMATION |
        FOF_NOERRORUI | FOF_SILENT;
    return SHFileOperation( &shf ) == 0;

}

BOOL WriteBinaryBytesToFile( LPCTSTR fileName, unsigned char* data, 
                       unsigned int datasize , BOOL bAppend )
{
    CAtlFile file;
    if( !bAppend && IsFileExist( fileName ))
        DeleteFiles( fileName );

    HRESULT ret = file.Create( fileName, FILE_WRITE_DATA, FILE_SHARE_WRITE, bAppend?OPEN_ALWAYS:CREATE_ALWAYS );
    if ( !SUCCEEDED( ret ) )
        return FALSE;
    if( bAppend )
    {
        file.Seek( 0, FILE_END );
    }
    unsigned char *pos = data;
    while( datasize > 0 )
    {
        DWORD dwWrite = 0;
        if ( file.Write( pos , datasize , &dwWrite ) != S_OK )
        {
            file.Close();
            return FALSE;
        }
        datasize -= dwWrite;
        pos += dwWrite;
    }
    file.Close();
    return TRUE;
}

BOOL GCreateFile(std::string& fileNamePath,
                std::string& fileNameExt,
                int shortNameLength,
                std::string& data)
{
    char c[] = "a";
    std::string fileName;
    fileName.append(fileNamePath);
    while( shortNameLength-- )
    {
        fileName.append(c);
        ++*c;
        if( *c > 'z' )
        {
            *c = 'a';
        }
    }
    fileName.append(fileNameExt);

    std::cout << "fileName:" << fileName << std::endl;
    std::cout << "fileName.size():"<< fileName.size() << std::endl;
    std::cout << "MAX_PATH" << MAX_PATH << std::endl;

    if( WriteBinaryBytesToFile(fileName.c_str(), (unsigned char*)data.data(), data.size(), FALSE ) )
    {
        std::cout << "++++++++++++++WriteBinaryBytesToFile successful.++++++++++++++" << std::endl;
        return TRUE;
    }
    else
    {
        std::cout << "==============WriteBinaryBytesToFile error==============." << std::endl;
        return FALSE;
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    std::string fileNamePath = "E:\\MyCPlusProject\\TestFileNameMaxLength\\TestFileNameMaxLength\\Output\\";
    std::string fileNameExt = ".txt";
    std::string data("This is a content.");
    
    int shortNameLength;
    shortNameLength = MAX_PATH - fileNameExt.size() - fileNamePath.size();
    GCreateFile(fileNamePath, fileNameExt, shortNameLength, data);

    std::cout << "------------------" << std::endl;
    shortNameLength = MAX_PATH - fileNameExt.size() - fileNamePath.size() - 1;
    GCreateFile(fileNamePath, fileNameExt, shortNameLength, data);

    return 0;
}

提示：右鍵項目屬性，將字符集設置為“未設置”。

posted on 2010-09-04 13:59 volnet 閱讀(4072) 評論(0)  編輯 收藏 引用