Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (W-Z)
Guardian Procedure Calls Reference Manual—522629-013
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WRITEREAD[X] Procedures
WRITEREAD[X] Procedures
Summary
Syntax for C Programmers
Syntax for TAL Programmers
Parameters
Condition Code Settings
Considerations
Considerations for WRITEREADX Only
Errors for WRITEREADX Only
Example
Related Programming Manuals
Summary
The WRITEREAD[X] procedures write data to a file from an array in the application
process, then waits for data to be transferred back from the file. The data from the
read portion returns in the same array used for the write portion.
WRITEREAD is intended for use with 16-bit addresses, while WRITEREADX is
intended for use with 32-bit extended addresses. Therefore, the data buffer for
WRITEREADX can be either in the caller’s stack segment or any extended data
segment.
If the file is opened for nowait I/O, you must not modify the buffer before the I/O
completes with a call to AWAITIOX. This condition also applies to other processes that
may be sharing the segment. The application must ensure that the buffer used in the
call to WRITEREADX is not reused before the I/O completes with a call to AWAITIOX.
Terminals A special hardware feature is incorporated in the asynchronous multiplexer
controller, which ensures that the system is ready to read from the terminal
as soon as the write is completed.
Interprocess Communication
The WRITEREAD[X] procedure is used to originate a message to another
process which was previously opened, then waits for a reply from that
process.