COMMTIMEOUTS - Win32 Programmer's Reference

Win32 Programmer's Reference

Home Index About

Custom Search

Overview

Group

Quick Info

Windows NT
Yes
Win95
Yes
Win32s
No
Import Library
-
Header File
winbase.h
Unicode
No
Platform Notes
None

COMMTIMEOUTS

The COMMTIMEOUTS structure is used in the SetCommTimeouts and GetCommTimeouts functions to set and query the time-out parameters for a communications device. The parameters determine the behavior of ReadFile, WriteFile, ReadFileEx, and WriteFileEx operations on the device.

typedef struct _COMMTIMEOUTS { // ctmo

DWORD ReadIntervalTimeout;

DWORD ReadTotalTimeoutMultiplier;

DWORD ReadTotalTimeoutConstant;

DWORD WriteTotalTimeoutMultiplier;

DWORD WriteTotalTimeoutConstant;

} COMMTIMEOUTS,*LPCOMMTIMEOUTS;

Members
ReadIntervalTimeout

Specifies the maximum time, in milliseconds, allowed to elapse between the arrival of two characters on the communications line. During a ReadFile operation, the time period begins when the first character is received. If the interval between the arrival of any two characters exceeds this amount, the ReadFile operation is completed and any buffered data is returned. A value of zero indicates that interval time-outs are not used.

A value of MAXDWORD, combined with zero values for both the ReadTotalTimeoutConstant and ReadTotalTimeoutMultiplier members, specifies that the read operation is to return immediately with the characters that have already been received, even if no characters have been received.

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 ReadTotalTimeoutMultiplier member and the requested number of bytes.

A value of zero for both the ReadTotalTimeoutMultiplier and ReadTotalTimeoutConstant members 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 WriteTotalTimeoutMultiplier member and the number of bytes to be written.

A value of zero for both the WriteTotalTimeoutMultiplier and WriteTotalTimeoutConstant members indicates that total time-outs are not used for write operations.

Remarks
If an application sets ReadIntervalTimeout and ReadTotalTimeoutMultiplier to MAXDWORD and sets ReadTotalTimeoutConstant to a value greater than zero and less than MAXDWORD, one of the following occurs when the ReadFile function is called:

If there are any characters in the input buffer, ReadFile returns immediately with the characters in the buffer.
If there are no characters in the input buffer, ReadFile waits until a character arrives and then returns immediately.
If no character arrives within the time specified by ReadTotalTimeoutConstant, ReadFile times out.

See Also
GetCommTimeouts, ReadFile, ReadFileEx, SetCommTimeouts, WriteFile, WriteFileEx

Last news from Greatis Software

    Nostalgia .Net     .Net is powerful, but not all-powerful, so sometimes we need to use Win32 API for our .Net applications. It's simple enough with Platform Invoke if you have Win32 skill, but we do not always have time to dig the ancient documentation, declare the special types that are compatible with Win32, find the values of the Win32's constants and so on. Nostalgia .Net offers several simple-to-use classes, and components that will allow you to forget about the headache of Win32 and just use the power of Win32 in your application the same way as you use the native. Net classes. More »

Recommended software for developers

    Ultimate Pack     Component pack for Delphi and C++ Builder that contains runtime form designer, runtime object inspector, print suite and much more for the very special price. More »

    Form Designer .Net     Unique runtime form design solution that allows to edit any form in .Net WinForms application at runtime with full source codes for only 300 euro! More »

    Print Suite .Net     Print Suite .Net is a set of components for easy printing texts, images and grids from your WinForms applications. Full C# source codes are available More »

    Gradient Controls .Net     Gradient Controls .Net offers controls with gradient background feature. Labels, panels and so on... Full C# source codes are available More »

    Greatis iGrid     iGrid plots drawing grid right over your desktop, so you can use it everywhere, with any drawing application without any special plugins for different graphic editors. More »

All the contacts and projects

Dmitry Vasiliev (just.dmitry)

More Online Helps

Win32 Programmer's Reference
Win32 Multimedia Programmer's Reference
OLE Programmer's Reference
Microsoft Windows Pen API Programmer's Reference
Microsoft Windows Sockets 2 Reference
Microsoft Windows Telephony API (TAPI) Programmer's Reference
Unix Manual Pages

greatis just4fun network