IStiUSD::RawReadData method

A still image minidriver's IStiUSD::RawReadData method reads data from a still image device.

Syntax


HRESULT RawReadData(
   LPVOID       lpBuffer,
   LPDWORD      lpdwNumberOfBytes,
   LPOVERLAPPED lpOverlapped
);

Parameters

lpBuffer

Caller-supplied pointer to a buffer to receive data read from the device.

lpdwNumberOfBytes

Caller-supplied pointer to a DWORD. The caller loads the DWORD with the number of bytes in the buffer pointed to by lpBuffer. The driver must replace this value with the number of bytes actually read.

lpOverlapped

Optional, caller-supplied pointer to an OVERLAPPED structure (described in the Microsoft Windows SDK documentation).

Return value

If the operation succeeds, the method should return S_OK. Otherwise, it should return one of the STIERR-prefixed error codes defined in stierr.h.

Remarks

A still image minidriver typically implements this method by calling ReadFile (described in the Windows SDK documentation).

For USB devices, better performance can be achieved if read requests are aligned to maximum packet size boundaries. Maximum packet sizes can be obtained by calling DeviceIoControl, specifying the IOCTL_GET_CHANNEL_ALIGN_RQST I/O control code.

Requirements

Target platform

Desktop

Header

Stiusd.h (include Stiusd.h)

See also

IStiDevice::RawReadData

 

 

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