使用 ReadFile 时，一半的读取缓冲区已损坏

Question

与 ReadFile 一起使用的一半缓冲区已损坏。无论缓冲区的大小如何，其中一半具有相同的损坏字符。我已经在寻找任何可能导致读取提前停止的因素，等等。如果我增加缓冲区的大小，我会看到更多的文件，所以它不会在文件的特定部分失败。

Visual Studio2019.Windows10.

#define MAXBUFFERSIZE 1024
DWORD bufferSize = MAXBUFFERSIZE;
_int64 fileRemaining;

HANDLE hFile;
DWORD  dwBytesRead = 0;
//OVERLAPPED ol = { 0 };
LARGE_INTEGER dwPosition;

TCHAR* buffer;

hFile = CreateFile(
    inputFilePath,         // file to open
    GENERIC_READ,          // open for reading
    FILE_SHARE_READ,       // share for reading
    NULL,                  // default security
    OPEN_EXISTING,         // existing file only
    FILE_ATTRIBUTE_NORMAL, // normal file    | FILE_FLAG_OVERLAPPED
    NULL);                 // no attr. template

if (hFile == INVALID_HANDLE_VALUE)
{
    DisplayErrorBox((LPWSTR)L"CreateFile");
    return 0;
}

LARGE_INTEGER size;
GetFileSizeEx(hFile, &size);

_int64 fileSize = (__int64)size.QuadPart;
double gigabytes = fileSize * 9.3132e-10;
sendToReportWindow(L"file size: %lld bytes \(%.1f gigabytes\)\n", fileSize, gigabytes);

if(fileSize > MAXBUFFERSIZE)
{
    buffer = new TCHAR[MAXBUFFERSIZE];
}
else
{
    buffer = new TCHAR[fileSize];
}
fileRemaining = fileSize;

sendToReportWindow(L"file remaining: %lld bytes\n", fileRemaining);

while (fileRemaining)                                       // outer loop. while file remaining, read file chunk to buffer
{
    sendToReportWindow(L"fileRemaining:%d\n", fileRemaining);

    if (bufferSize > fileRemaining)                         // as fileremaining gets smaller as file is processed, it eventually is smaller than the buffer
        bufferSize = fileRemaining;

    if (FALSE == ReadFile(hFile, buffer, bufferSize, &dwBytesRead, NULL))
    {
        sendToReportWindow(L"file read failed\n");
        CloseHandle(hFile);
        return 0;
    }

    fileRemaining -= bufferSize;

 // bunch of commented out code (verified that it does not cause the corruption)
}
delete [] buffer;

调试器html视图（512 字节缓冲区）

调试器html 视图（1024 字节缓冲区）。这表明该文件可能不是损坏的来源。

杂项说明：有人告诉我，文件的内存映射没有任何优势，因为我是按顺序处理文件的。这种方法的另一个优点是，当我在 WARC 文件中检测到特定的和重复出现的标签时，我可以向前跳过约 500 个字节并继续处理。这提高了速度。

Answer 1

原因是你使用了TCHAR类型的缓冲数组，TCHAR类型的大小是2个字节。所以调用ReadFile函数时设置的bufferSize实际上是每2个字节填充到buffer数组中的。

但是缓冲区的实际大小是 sizeof(TCHAR) * fileSize，所以您看到的缓冲区数组的一半是“损坏的”

使用 ReadFile 时，一半的读取缓冲区已损坏

Half of read buffer is corrupt when using ReadFile

c++

winapi

readfile

warc