GEOS SDK TechDocs
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1 Using Streams: The Basics
It is often useful for an application to be able to write out data in an orderly manner to be read by another program or sent to a device such as a printer or modem. GEOS provides a mechanism called a stream to allow an orderly flow of data between two programs, between two threads of a multi-threaded program, or between a program and a device such as a serial or parallel port. The stream interface includes various ways to notify a program that bytes are available to read, or that there is room to write additional data.
The GEOS parallel and serial port drivers use the stream mechanism, so programs that will use these ports must do so via this mechanism; however, libraries exist to handle some of the more common uses for port communications. Programs do not need to access the serial or parallel ports in order to print because the spooler does it for them. For more information about the spooler and printing, see .
This chapter may be read with only a general understanding of GEOS and Object Assembly. Messaging is used heavily in informing the application using a stream of the stream's status, so a good understanding of object-oriented programming will be helpful. You should also be familiar with the GEOS memory manager. The chapter is divided into three main sections:
1 Using Streams: The Basics
1.1 Initializing a Stream
1.2 Blocking on Read or Write
1.3 Writing Data to a Stream
1.4 Reading Data from a Stream
1.5 Shutting Down a Stream
1.6 Miscellaneous Functions
2 Using the Serial Ports
2.1 Initializing a Serial Port
2.2 Communicating
2.3 Closing a Serial Port
3 Using the Parallel Ports
3.1 Initializing a Parallel Port
3.2 Communicating
3.3 Closing a Parallel Port
GEOS SDK TechDocs
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| 1 Using Streams: The Basics