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This structure is used in the SetCommTimeoutsand GetCommTimeoutsfunctions to set and query the time-out parameters for a communication device. The parameters determine the behavior of the ReadFileand WriteFilefunction operations on the device.
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. During a ReadFileoperation, the time period begins when the first character is received. If the interval between the arrival of any two characters exceeds this amount, the ReadFileoperation is completed and any buffered data is returned. A value of zero indicates that interval time-outs are not used.
- ReadTotalTimeoutMultiplier
- Specifies the multiplier, in milliseconds, used to calculate the total time-out 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 time-out 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 both the ReadTotalTimeoutMultiplierand ReadTotalTimeoutConstantmembers indicates that total time-outs are not used for read operations.
- WriteTotalTimeoutMultiplier
- Specifies the multiplier, in milliseconds, used to calculate the total time-out 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 time-out 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 both the WriteTotalTimeoutMultiplierand WriteTotalTimeoutConstantmembers indicates that total time-outs are not used for write operations.
Remarks
If an application sets ReadIntervalTimeoutand ReadTotalTimeoutMultiplierto MAXDWORD and sets ReadTotalTimeoutConstantto a value greater than zero and less than MAXDWORD, one of the following occurs when the ReadFilefunction is called:
- If there are any 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
Runs On Versions Defined in Include Link to Windows CE OS 1.0 and later Winbase.h Note This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.
See Also
GetCommTimeouts, ReadFile, SetCommTimeouts, WriteFile