COBOL Define Your Own File Handler

最新推荐文章于 2021-05-01 18:29:46 发布

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最新推荐文章于 2021-05-01 18:29:46 发布

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本文介绍如何使用COBOL或C等语言创建自定义文件处理器(File Handler)，并提供了示例代码来展示如何将OUTPUT模式更改为EXTEND模式。此外，还介绍了如何在应用程序中启用和调用这些自定义处理器。

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What's User Defined File Handler

Customers can build some kind of their own file handler, inner the handler you can change default operation behavior. For example you can change “OUTPUT” mode to “EXTEND” mode when some criteria matched.

How to Implement a File Handler

File handler can be written in COBOL or C, or else, if you like, but COBOL is preferred, because it’s more convenient, and our caller programs are written in COBOL either.

File handler is nothing but a general COBOL program with specific parameters, it should be compiled into a .gnt/or .so file using compiler.

An File Handle Sample

This sample is trying to change “OUTPUT” open-mode to “EXTEND” open-mode for all line sequential and sequential dataset, and forward all other dataset operation to default handler, i.e, “EXTFH”.

     1         IDENTIFICATION DIVISION.
     2         PROGRAM-ID.    MYEXTFH.
     3         DATA DIVISION.
     4         WORKING-STORAGE SECTION.
     5
     6         LINKAGE SECTION.
     7         01  Action-Code.
     8             03  Action-Type                  PIC X(01).
     9             03  Cobol-Op                     PIC X(01).
    10                 78  Open-Output                 value x'01'.
    11                 78  Open-Extend                 value x'03'.
    12         01  FCD-Area.
    13             COPY "XFHFCD.CPY".
    14         01  FILE-DD-NAME                        PIC X ANY LENGTH.
    15
    16         PROCEDURE DIVISION USING Action-Code FCD-Area.
    17             DISPLAY "IN MY FILE HANDLER".
    18             IF Cobol-Op = Open-Output
    19                AND (FCD-Organization = 0 OR      *> Line sequential
    20                     FCD-Organization = 1 )       *> Sequential
    21
    22                SET ADDRESS OF FILE-DD-NAME TO FCD-FILENAME-ADDRESS
    23                DISPLAY "DD=" FILE-DD-NAME(1:FCD-Name-Length)
    24
    25                MOVE Open-Extend TO Cobol-Op
    26             END-IF.
    27
    28             CALL "EXTFH" USING ACTION-CODE FCD-AREA.
    29             EXIT PROGRAM.
    30

How to use a File Handler

The only thing we have to do is notifying caller that there is a new handler, please call me; this is implemented by add compiling option CALLFH(“HANDLENAME”) for Micro Focus compiler and xxx-extfh=HANDLENAME, and xxx-extfh-lib="HANDLELIBNAME" for COBOL-IT compiler (xxx can be isam or flat) while compiling caller application programs.