IEDTGTM - Read a marked record

This access function makes it possible to search for a marked record starting at a specific line number (EDTKEY1).
The direction of the search can also be specified.

It is only possible to search for marked records. It is not possible to search for a specific mark.

Searches can be performed in the work files 0..22. No marked records can be read in a work file in which a file has been opened for real processing by means of @OPEN (format 2). The access attempt is rejected with a return code.

Searching for a marked record

In order to search for a marked record it is necessary to specify the following:

• Work file ($0..$22) in the field EAMFILE (EDTAMCB):
  Work file in which the marked record is to be read.

• Line number of a file record in the buffer EDTKEY1 (the record does not have to exist).

• Displacement n (0,+1,-1) in the field EAMDISP (EDTAMCB):
  Specification of the search direction (other positive values for displacement are handled like +1, and other negative values are handled like -1)

• Character set in which the record is to be made available, in the field EGLCCSN (EDTGLCB)

Two types of search are possible:

• Search for a specific line number

• Search for the next marked record relative to a specified line number

Reading a marked record with a specific line number

Displacement specification: n = 0

If the value 0 is specified for the displacement (EAMDISP) then the record with the specified line number (EDTKEY1) is read. If this record is not present or if the record has no marks then the next marked record (possibly the first or last record) is read and transferred.

Summary of the return codes and the read record:

EDTKEY1	EAMDISP	EGLMRET	EAMSR1	EDTREC
Line number of an existing record	0	EAMRETOK	EAMOK00	Record with record number
Smaller than line number of first marked record	0	EAMRETOK	EAMOK08	First record with mark
Larger than line number of last marked record	0	EAMRETOK	EAMOK12	Last record with mark
Larger than line number of first marked record and smaller than line number of last marked record and not a line number of a marked record	0	EAMRETOK	EAMOK04	Next marked record after EDTKEY1
Work file is empty or contains no marked records		EAMACERR	EAMAC16

If the search is successful, EDT passes the line number of the record that was actually read in EDTKEY together with the record mark in EAMMARK (EDTAMCB).

For the meaning of the return codes, see section “EDTGLCB - Global EDT control block”.

Reading the next marked record

Displacement specification n = +1 or -1

The next marked record before or after a specific line number is searched for (EDTKEY1).

n = +1:	the first marked record after the specified line number is read
n = -1:	the first marked record before the specified line number is read

If no further marked records are present in the specified direction then the first or last marked record is read and transferred.

Summary of the return codes and the read record:

EDTKEY1	EAMDISP	EGLMRET	EAMSR1	EDTREC
EDTKEY1 = XXXXXXXX	+1 Record with mark exists after EDTKEY1	EAMRETOK	EAMOK00	Next record with mark after EDTKEY1
EDTKEY1 = XXXXXXXX	-1 Record with mark exists before EDTKEY1	EAMRETOK	EAMOK00	Next record with mark before EDTKEY1
EDTKEY1 = XXXXXXXX	+1 No record with mark after EDTKEY1	EAMRETOK	EAMOK12	Last marked record
EDTKEY1 = XXXXXXXX	-1 No record with mark before EDTKEY1	EAMRETOK	EAMOK08	First marked record
Work file is empty or contains no marked records		EAMACERR	EAMAC16

If the search is successful, EDT passes the line number of the record that was actually read in EDTKEY together with the record mark in EAMMARK (EDTAMCB).

For the meaning of the return codes, see section “EDTGLCB - Global EDT control block”.

Call

The following specifications are required (see overview):

• Entry of values in the required fields in the EDTGLCB and EDTAMCB control blocks.

• Entry of values in the EDTKEY1 buffer

• Provision of storage space for the buffers EDTKEY and EDTREC

• Call of the entry point address IEDTGTM with the parameter list

Overview

(For the control blocks, see section “EDTGLCB - Global EDT control block”).

Entry point address     :     IEDTGTM

Parameter list         :     A (EDTGLCB, EDTAMCB, EDTKEY1, EDTKEY,

EDTREC)

Call parameter		Return parameter
EDTGLCB:	EGLUNIT EGLVERS EGLCCSN	EDTGLCB:	EGLRETC EGLRMSG
EDTAMCB:	EAMUNIT EAMVERS EAMFLAG EAMFILE EAMDISP EAMLKEY1 EAMPKEY EAMPREC	EDTAMCB:	EAMMARK EAMLKEY EAMLREC
EDTKEY1 EDTKEY EDTREC		EDTKEY EDTREC

Return parameters on successful record access:

Alongside the EGLRETC field in EDTGLCB (EGLMRET = EAMRETOK), EDT specifies the following parameters:

Record	EDTREC
Record length	EAMLREC in EDTAMCB
Line number	EDTKEY (always 8 bytes in length)
Length of line number	EAMLKEY in EDTAMCB (always 8 bytes)
Record mark	EAMMARK in EDTAMCB

If the buffer length (EAMPREC) is not sufficient to accommodate the record, EAMACERR is entered for EGLMRET and EAMAC12 is entered for EGLSR1. The record is truncated. The actual length read is entered in the EAMLREC field in AMCB. In compatibility mode (as in EDT V16.6B), the buffer length required to read the record in full is stored here.

In Unicode mode, however, it is necessary to specify the number of bytes actually transferred since multi-byte coding always requires the record to be truncated between two valid characters and, consequently, fewer bytes may be transferred than are specified in EAMPREC.

Call in the C program

Required include files:

#include <stdio.h>

#include <iedtgle.h>

The control block EDTAMCB is declared and initialized as follows (the value 4096 here was selected as an example of the maximum expected record length):

iedamcb amcb = IEDAMCB_INIT;
char key1[8]; 
char key[8]; 
char rec[4096]; 
ambc.length_key1 = 8; 
amcb.length_key_outbuff = 8;
amcb.length_rec_outbuff = 4096;

The specifications for the other parameters are user-dependent. If, for example, the
next marked record after the record with line number 123.4 in work file 22 is searched for:

strncpy(amcb.filename,"$22     ",8); 
strncpy(key1,"01234000",8); 
amcb.displacement = 1; 

In the C program, the IEDTGTM function is called as follows:

IEDTGTM(&glcb,&amcb,key1,key,rec);