"IBM Mainframe Assembler List" <[email protected]> wrote on
02/12/2022 10:11:13 PM:
> You could PACK the field, or just the last byte (which is just a
> nibble-swap), and CP to =P'0'. The cond. code tells you what you want
to
> know.
I have to use PKA instead of PACK because the zoned data can be up
to 31 bytes in length and PKA doesn't set the condition code. Yes, you
said I could just PACK the last byte but I think I prefer bit testing
similar to the following.
> Or, you could use
> IF TM,lastByte,B'11110000',O
> It's + F (or not signed, if you like that interpretation)
> ELSEIF TM,lastByte,B'00010000',O
> It's - B or D
> ELSE
> It's + A, C, or E
> ENDIF
> Note that this is a pure sign check, i.e. 0 is not special.
>
> The last is more instructions, but I'd guess that it would perform the
best
> if that matters.
In line with the above, I will consider zoned data that ends with
anything less than x'A0' to be invalid and will just return it to the
caller as it was in the record. Otherwise, I will PKA/CVBG it and then
negate it (because PKA ignores overpunch signs and forces a packed x'.C'
sign) if the original last byte passes the following test.
IF 0(R3),(NO,TM),X'F0' IF WAS NEGATIVE
AND 0(R3),(ON,TM),X'10'
MGHI R2,-1 NEGATE THE 64-BIT NUMBER
ENDIF
After that, I will convert it back to zoned data with a floating
left sign and an optional decimal point using EDMK. I will use just two
edit masks and dynamically place the optional decimal point in the second
one. I will also dynamically place the significance byte depending upon
whether I want to keep leading zeroes or not.
MASK0 DC x'402020202020202020202020202020202020202020202020202020-
20202020206040'
MASK1 DC x'402020202020202020202020202020202020202020202020202020-
20202020202060'
Sincerely,
Dave Clark
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