Question

我创建了一个文件：

m_fileHandle = CreateFileA( 
            m_pszFilename,          
            GENERIC_WRITE,          
            0,                      
            NULL,                   
            CREATE_ALWAYS,          
            FILE_ATTRIBUTE_NORMAL | FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH,
            NULL);

然后写信给它：

const BOOL bSuccess  = WriteFile(
        m_fileHandle, 
        buffer, 
        dataSize,
        &tempBytesWritten, 
        NULL );

当我启动程序时，WriteFile失败，GetLastError（）返回错误87.

我读到，当dataSize不是硬盘扇区大小的倍数时，使用标志FILE_FLAG_NO_BUFFERING创建的文件上的WriteFile会失败。如果这是错误的原因，那么为什么我在Visual Studio Express 2012中调试时代码工作正常？

Answer 1

解决方案在这里：文件缓冲https://msdn.microsoft.com/en-us/library/windows/desktop/cc644950%28v=vs.85%29.aspx

工作代码：

#include "stdafx.h"
#include "assert.h"
#include <iostream>
#include <Windows.h>
#include <comutil.h>

using namespace std;

namespace{

    unsigned long tempBytesWritten = 0;
    HANDLE m_fileHandle;
    char m_pszFilename[_MAX_PATH] = "";

    // Create a temporary file for benchmark
    int createFile()
    {
        WCHAR tempPath[MAX_PATH];
        GetTempPath(_countof(tempPath), tempPath);
        _bstr_t p(tempPath);
        const char* c = p;
        strcpy(m_pszFilename, c);
        strcat(m_pszFilename, "testRawFile.raw");
        cout << "Writing to " << m_pszFilename << endl;

        m_fileHandle = CreateFileA( 
            m_pszFilename,          
            GENERIC_WRITE,          
            0,                      
            NULL,                   
            CREATE_ALWAYS,          
            FILE_ATTRIBUTE_NORMAL | FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH,
            NULL);

        if (m_fileHandle == INVALID_HANDLE_VALUE) 
        {
            assert( false );
        }
        return 0;
    }
}

DWORD DetectSectorSize( WCHAR * devName, PSTORAGE_ACCESS_ALIGNMENT_DESCRIPTOR pAlignmentDescriptor)
 {
  DWORD                  Bytes   = 0;
  BOOL                   bReturn = FALSE;
  DWORD                  Error   = NO_ERROR;
  STORAGE_PROPERTY_QUERY Query;

  ZeroMemory(&Query, sizeof(Query));

  HANDLE  hFile = CreateFileW( devName,
                               STANDARD_RIGHTS_READ, 
                               FILE_SHARE_READ | FILE_SHARE_WRITE,
                               NULL, 
                               OPEN_EXISTING, 
                               FILE_ATTRIBUTE_NORMAL,
                               NULL);

  if (hFile==INVALID_HANDLE_VALUE) {
    wprintf(L"  hFile==INVALID_HANDLE_VALUE. GetLastError() returns %lu.\n", Error=GetLastError());
    return Error;
   }

  Query.QueryType  = PropertyStandardQuery;
  Query.PropertyId = StorageAccessAlignmentProperty;

  bReturn = DeviceIoControl( hFile, 
                             IOCTL_STORAGE_QUERY_PROPERTY, 
                             &Query, 
                             sizeof(STORAGE_PROPERTY_QUERY), 
                             pAlignmentDescriptor,
                             sizeof(STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR), 
                             &Bytes,
                             NULL);

  if (bReturn == FALSE) {
    wprintf(L"  bReturn==FALSE. GetLastError() returns %lu.\n", Error=GetLastError());
   }

  CloseHandle(hFile);
  return Error;

 }


int main()
{
    unsigned int dataSize = 2000;

    DWORD                               Error     = NO_ERROR;
    STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR Alignment = {0};
    //  WCHAR                               szDisk[]  = L"\\\\.\\PhysicalDrive0";
    WCHAR                               szDisk[]  = L"\\\\.\\C:";

    Error = DetectSectorSize(szDisk, &Alignment);
    if (Error) {
        wprintf(L"Error %lu encountered while querying alignment.\n", Error);
        return Error;
    }

    wprintf(L"Disk %s Properties\n", (WCHAR*) szDisk);

    if (Alignment.BytesPerLogicalSector < Alignment.BytesPerPhysicalSector) {
        wprintf(L"  Emulated sector size is %lu bytes.\n", Alignment.BytesPerLogicalSector);
    }

    wprintf(L"  Physical sector size is %lu bytes.\n", Alignment.BytesPerPhysicalSector);

    dataSize = ((unsigned int)(dataSize + Alignment.BytesPerPhysicalSector - 1)/Alignment.BytesPerPhysicalSector) * Alignment.BytesPerPhysicalSector;

    // Allocate buffer for file
    unsigned char *buffer = new unsigned char[dataSize];

    // Create file to write to
    if ( createFile() != 0 )
    {
        printf("There was error creating the files... press Enter to exit.");
        getchar();
        return -1;
    }

    const BOOL bSuccess  = WriteFile(m_fileHandle, buffer, dataSize, &tempBytesWritten, NULL ); 

    if (!bSuccess)
    {
        cout << "Write failed with error " << GetLastError() << endl;
    }

    // clean up and remove file
    CloseHandle(m_fileHandle);
    wchar_t wtext[_MAX_PATH];
    mbstowcs(wtext, m_pszFilename, strlen(m_pszFilename)+1);
    DeleteFile(wtext);

    return 0;
}

WriteFile失败，错误87（参数不正确）但在Visual Studio中调试时工作正常

1 个答案: