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4/8/2010

This structure is used in the SetCommTimeoutsand GetCommTimeoutsfunctions to set and query the timeout parameters for a communication device.

The members determine the behavior of the ReadFileand WriteFilefunction operations on the device.

Syntax 

typedef struct _COMMTIMEOUTS {
  DWORD 
ReadIntervalTimeout;
  DWORD 
ReadTotalTimeoutMultiplier;
  DWORD 
ReadTotalTimeoutConstant;
  DWORD 
WriteTotalTimeoutMultiplier;
  DWORD 
WriteTotalTimeoutConstant;
} COMMTIMEOUTS,*LPCOMMTIMEOUTS;

Members

ReadIntervalTimeout

Specifies the maximum acceptable time, in milliseconds, to elapse between the arrival of two characters on the communication line.

In Windows Embedded CE, during a ReadFileoperation, the time period begins immediately.

If the interval between the arrivals of two characters exceeds the time amount specified in ReadIntervalTimeout, the ReadFileoperation is completed and buffered data is returned.

A value of zero indicates that interval timeouts are not used.

ReadTotalTimeoutMultiplier

Specifies the multiplier, in milliseconds, used to calculate the total timeout period for read operations.

For each read operation, this value is multiplied by the requested number of bytes to be read.

ReadTotalTimeoutConstant

Specifies the constant, in milliseconds, used to calculate the total timeout period for read operations.

For each read operation, this value is added to the product of the ReadTotalTimeoutMultipliermember and the requested number of bytes.

A value of zero for the ReadTotalTimeoutMultiplierand ReadTotalTimeoutConstantmembers indicates that total timeouts are not used for read operations.

WriteTotalTimeoutMultiplier

Specifies the multiplier, in milliseconds, used to calculate the total timeout period for write operations.

For each write operation, this value is multiplied by the number of bytes to be written.

WriteTotalTimeoutConstant

Specifies the constant, in milliseconds, used to calculate the total timeout period for write operations.

For each write operation, this value is added to the product of the WriteTotalTimeoutMultipliermember and the number of bytes to be written.

A value of zero for the WriteTotalTimeoutMultiplierand WriteTotalTimeoutConstantmembers indicates that total timeouts are not used for write operations.

Remarks

If an application sets ReadIntervalTimeoutand ReadTotalTimeoutMultiplierto MAXDWORDand sets ReadTotalTimeoutConstantto a value greater than zero and less than MAXDWORD, one of the following occurs when the ReadFilefunction is called:

  • If there are characters in the input buffer, ReadFilereturns immediately with the characters in the buffer.

  • If there are no characters in the input buffer, ReadFilewaits until a character arrives and then returns immediately.

  • If no characters arrive within the time specified by ReadTotalTimeoutConstant, ReadFiletimes out.

Requirements

Header winbase.h
Windows Embedded CE Windows CE 1.0 and later
Windows Mobile Windows Mobile Version 5.0 and later

See Also