Write

Sends data to a device.

Syntax

virtual HRESULT Write(char ch, bool bFlush = true, long lTimeout = CUR_TIMEOUT) abstract;

virtual HRESULT Write(BYTE* pBuf, long cbDesired, long* pcbActual = NULL, bool bFlush = true, long lTimeout = CUR_TIMEOUT) abstract;

virtual HRESULT Write(SAFEARRAY* psaBuf, long cbDesired = -1, long* pcbActual = NULL, bool bFlush = true, long lTimeout = CUR_TIMEOUT) abstract;

Parameters

[in] Single character to send to the device.

pBuf

[in] Array of bytes to send to the device.

psaBuf

[in] SAFEARRAY of bytes to send to the device. if cbDesired is -1, all elements of the SAFEARRAY are sent.

cbDesired

[in] Number of elements (bytes) to send to the device. If set to -1 and the input is a SAFEARRAY, then all elements of the SAFEARRAY are sent.

pcbActual

[out] Actual number of elements (bytes) sent to the device.

bFlush

[in] If true, the formatted I/O write buffer is flushed to the device.

lTimeout

[in] I/O timeout value in milliseconds.

Return value

Returns S_OK if successful, otherwise a failure HRESULT.

Remarks

The Write function sends raw bytes to the formatted I/O write buffer. If the bFlush parameter is true, then the contents of the I/O write buffer are flushed to the device. If bFlush is false, then the data is queued in the write buffer until the buffer is full or a subsequent operation forces a flush. Queueing data in this fashion can improve I/O performance by reducing the number of I/O roundtrips to the device.

Example

The following example demonstrates use of the Write function.

STDMETHODIMP Acme4321::IAcme4321_Configure(BYTE chData, SAFEARRAY* psaData)
{
  HRESULT hr = S_OK;

  // Queue up individual characters in the write buffer
  hr = io.Write('A', false);
  hr = io.Write('B', false);
  hr = io.Write(chData, false);

  // Send array of bytes and flush buffer to device
  hr = io.Write(psaData);

  return hr;
}