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How Fielded Buffers Are Implemented with FML
Fielded buffers are created, updated, accessed, input, and output via Field Manipulation Language (FML). FML provides:
FML is implemented as a library of functions and macros that can be called from C programs. It provides a separate set of functions for:
The last set of functions listed above constitutes the FML VIEWS software. VIEWS is a set of functions that exchange data between FML fielded buffers and structures in C or COBOL language application programs. When a program receives a fielded buffer from another process, the program has the choice of:
If you need to perform lengthy manipulations on buffer data, the performance of your program can be improved by transferring fielded buffer data to structures or records, and operating on the data using normal C or COBOL statements. Then you can put the data back into a fielded buffer (again using VIEWS functions), and send the buffer off to another process.
Before you can use VIEWS, you must set up your program such that it can recognize the format of incoming fielded buffer data. You can do this setup task by using a set of view descriptions kept in a cache on your system.
A view description is created and stored in a source viewfile. The view description maps fields in fielded buffers to members in C structures or COBOL records. The source view descriptions are compiled, and can then be used to map data transferred between fielded buffers and C structures or COBOL records in a program.
By keeping view descriptions cached in a central file, you can increase the data independence of your programs; you only need to change the view description(s) and recompile them to effect changes in data format throughout an application that uses VIEWS.
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