New string key feature for TPFDF

TPFUG_Req_Number: DF05180F
Contact Originator Id: michael.bahlen@klm.com
Abstract: To make the search within TPFDF on zero terminated strings possible a
key type is to be introduced that I call string key.
Description: To search/sort within the last field within an TPFDF Lrec that contains a variable length string (zero terminated) a lot of 'own' code is needed to avoid dumps (CTL-4). Or a lot of difficult key settings are needed.
To make this more simple a new key type is to be introduced. This key type should be based on the CLST instruction.
Critical Success Factors: The main success factor is the hardware used within the TPF environment.
As this solution needs the CLST instruction which is not available in older hardware configurations.
Another success factor is the availability of R0 during key instruction execution and an extra register to address the field within the record for the CLST instruction.
Alternative Solutions: No alternative solutions known
Solution Considerations: The solution for this requirement is to be split in two. One solution for assembler and one for C.

C solution
In the set of defines for key type instructions a new one the DF_STRING must be added.
The key generator must be adapted to generate a CLST instruction for these type of keys i.s.o. a CLC instruction.

ASM solution
In the key setting part of the TPFDB macro's a new sub-keyword is to be implemented.
This could look like S=Z/label to indicate a zero terminated string will be searched for.
This should work as the normal S= keyword, but invalidates the L= keyword and generates a CLST instruction i.s.o. the CLC
instruction.
Also the DBSETK macro is to be updated accordingly.
#DF_STRING as the new keyword working as the ID1= keyword.