TROO and TROT managed to escape my notice for the last decade. Thanks for sharing!
-----Original Message----- From: IBM Mainframe Assembler List [mailto:[email protected]] On Behalf Of Tony Harminc Sent: Monday, January 31, 2022 10:18 PM To: [email protected] Subject: Re: Making Encoded Bits Human Readable Caution! This message was sent from outside your organization. On Mon, 31 Jan 2022 at 15:55, Dave Clark <[email protected]> wrote: > Good deal. I replaced the following 104 bytes of machine code... ... > ...with the following 38 bytes of machine code. Thanks. Here's a different approach, though if you are primarily looking to economize on code bytes, it may not be for you. It uses a 256-byte table to contain the possible output values, and just translates the input to output directly. (I'm assuming that the bits to the right of the top four may not be zero.) SR R0,R0 Test char not in table (for older machines) LA R1,TABLE1 -> 256-byte table LA R3,RECBUF+108 -> Input byte LA R6,CWORK -> One output byte LHI R7,1 Length of input in bytes TROO TROO R6,R3,B’0001’ Translate with no test BC 3,TROO Unlikely, but be safe TABLE1 DS 0D Critical alignment! Input values DC C'1111111111111111' 00-0F DC C'1111111111111111' 10-1F DC C'1111111111111111' 20-2F DC C'1111111111111111' 30-3F DC C'2222222222222222' 40-4F DC C'2222222222222222' 50-5F DC C'2222222222222222' 60-6F DC C'2222222222222222' 70-7F DC C'3333333333333333' 80-8F DC C'3333333333333333' 90-9F DC C'3333333333333333' A0-AF DC C'3333333333333333' B0-BF DC C'4444444444444444' C0-CF DC C'4444444444444444' D0-DF DC C'4444444444444444' E0-EF DC C'4444444444444444' F0-FF The above handles only the first of your two sets of two bits, and a different table is needed to deal with the second. But it can all be done in a single translate with the right table: SR R0,R0 Test char not in table (for older machines) LA R1,TABLE2 -> 512-byte table LA R3,RECBUF+108 -> Input byte LA R6,CWORK -> Two output bytes LHI R7,1 Length of input in bytes TROT TROT R6,R3,B’0001’ Translate with no test BC 3,TROT Unlikely, but be safe TABLE2 DS 0D Critical alignment! Input values DC C'11111111111111111111111111111111' 00-0F DC C'12121212121212121212121212121212' 10-1F DC C'13131313131313131313131313131313' 20-2F DC C'14141414141414141414141414141414' 30-3F DC C'21212121212121212121212121212121' 40-4F DC C'22222222222222222222222222222222' 50-5F DC C'23232323232323232323232323232323' 60-6F DC C'24242424242424242424242424242424' 70-7F DC C'31313131313131313131313131313131' 80-8F DC C'32323232323232323232323232323232' 90-9F DC C'33333333333333333333333333333333' A0-AF DC C'34343434343434343434343434343434' B0-BF DC C'41414141414141414141414141414141' C0-CF DC C'42424242424242424242424242424242' D0-DF DC C'43434343434343434343434343434343' E0-EF DC C'44444444444444444444444444444444' F0-FF This isn't a complete drop-in for your code because it produces the two output value in adjacent bytes at CWORK, but perhaps you can accept that, or if not, you can copy the second byte to the right place. lease excuse typos; I haven't actually built or tested this. One could write a simple macro to generate the table from the bit field sizes and range, and it could handle any number of bytes with the same bit layout within each byte. Of course I wouldn't seriously recommend this approach for dealing with one byte, but it does show how powerful TROT in particular can be. I've been using it to produce printable hex fields for a few years, and it sure beats an UNPK loop. I'm sure there are other innovative uses for it. Tony H.
