ERROR_SHARING_VIOLATION - 有點白說

關於 ERROR_SHARING_VIOLATIOn 這個 error.
MS 的解釋

就是說，Windows 是一個 multi-tasking 的 OS，所以有人跟你同時在 access 一個 file，而且又同時 write....(有點看圖說故事的感覺)

所以有這個error 是很正常的事。

MS提供一個 sample code:

#define MAXRETRIES  5
#define RETRYDELAY  250

HANDLE  hFile     = INVALID_HANDLE_VALUE
DWORD   dwRetries = 0;
BOOL    bSuccess  = FALSE;
DWORD   dwErr     = 0;

do
{
    hFile = CreateFile( szFile,
                        GENERIC_READ,
                        FILE_SHARE_READ | FILE_SHARE_WRITE,
                        NULL,
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,
                        NULL);
    if ( INVALID_HANDLE_VALUE == hFile )
    {
        dwErr = GetLastError();

        if ( ERROR_SHARING_VIOLATION == dwErr )
        {
            dwRetries += 1;
            Sleep(RETRYDELAY);
            continue;
        }
        else
        {
            // An error occurred.
            break;
        }
    }

    bSuccess = TRUE;
    break;
} while ( dwRetries < MAXRETRIES );

if  ( bSuccess )
{
    // You succeeded in opening the file.
}
else
{
    // Failure occurs. Do graceful error handling.

    // Here, you must notify the user of the failure.

MessageBox( NULL,
            "Tried to update data file but it was already in use",
            "Update error...",
            MB_OK | MB_ICONSTOP );

    // You also want to put the software back in the state it was in
    // on entrance of the current function, as if the user had never
    // tried to do the update.

    // This may also require deallocating any resources that were
    // allocated because of this operation.
}

就是有這個 error 的時候，就 sleep 一下，等那個好心的程式write 結束，再 試一次。

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Windows XP 還有話說，因為一堆不知名的程式在background 跑 (virus scan, source control.. speed hd.. etc)

但是 Windows CE 還有這樣的error 真是.. 見鬼了