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Simple Displayable Hex to
Binary Conversion
I recently had the
misfortune of reviewing the most dreadful piece of code to convert
character (displayable) hexadecimal to binary. This tortured routine
used all manner of 'or', 'shift' and other instructions. Much
like my other example of converting binary
to displayable hexadecimal, the opposite conversion can also be
accomplished with only two instructions. Here's
a code snippet illustrating the technique using and TR, PACK and TRT to
validate the hexadecimal data:
.
.
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MVC HEXDIS,ANYDATA
Move some data to
convert
* to
HEXDIS.
*
LA
R2,8
Initialize return code.
TRT HEXDIS,HEXTRT
Validate the
displayable hex.
LTR R15,R2
Set the return code.
*
* RC = X'00' If all characters
are valid hex.
* RC = X'08' If any character is
not valid hex.
*
BNZR R14
Return to caller if invalid.
*
HEXOK DS 0H
TR HEXDIS,HEXBTR
Translate F0-C6 to
00-0F.
*
PACK HEXBIN(L'HEXBIN+1),HEXDIS(L'HEXDIS+1)
*
* HEXBIN now contains the binary
representation
* of HEXDIS.
*
BR R14
Return to caller.
.
.
.
CNOP
0,4
Fullword alignment.
HEXTRT EQU *
256 byte hex validation table.
SPACE ,
DC
XL16'08080808080808080808080808080808' 00 - 0F
DC
XL16'08080808080808080808080808080808' 10 - 1F
DC
XL16'08080808080808080808080808080808' 20 - 2F
DC
XL16'08080808080808080808080808080808' 30 - 3F
DC
XL16'08080808080808080808080808080808' 40 - 4F
DC
XL16'08080808080808080808080808080808' 50 - 5F
DC
XL16'08080808080808080808080808080808' 60 - 6F
DC
XL16'08080808080808080808080808080808' 70 - 7F
DC
XL16'08080808080808080808080808080808' 80 - 8F
DC
XL16'08080808080808080808080808080808' 90 - 9F
DC
XL16'08080808080808080808080808080808' A0 - AF
DC
XL16'08080808080808080808080808080808' B0 - BF
* Displayable
A B C D E F
DC
XL16'08000000000000080808080808080808' C0 - CF
DC
XL16'08080808080808080808080808080808' D0 - DF
DC
XL16'08080808080808080808080808080808' E0 - EF
* Displayable 0 1 2 3 4 5
6 7 8 9
DC
XL16'00000000000000000000080808080808' F0 - FF
SPACE ,
HEXBTR EQU *
256 byte hex conversion table.
SPACE ,
DC
XL16'00000000000000000000000000000000' 00 - 0F
DC
XL16'00000000000000000000000000000000' 10 - 1F
DC
XL16'00000000000000000000000000000000' 20 - 2F
DC
XL16'00000000000000000000000000000000' 30 - 3F
DC
XL16'00000000000000000000000000000000' 40 - 4F
DC
XL16'00000000000000000000000000000000' 50 - 5F
DC
XL16'00000000000000000000000000000000' 60 - 6F
DC
XL16'00000000000000000000000000000000' 70 - 7F
DC
XL16'00000000000000000000000000000000' 80 - 8F
DC
XL16'00000000000000000000000000000000' 90 - 9F
DC
XL16'00000000000000000000000000000000' A0 - AF
DC
XL16'00000000000000000000000000000000' B0 - BF
*
Binary
A B C D E F
DC
XL16'000A0B0C0D0E0F000000000000000000' C0 - CF
DC
XL16'00000000000000000000000000000000' D0 - DF
DC
XL16'00000000000000000000000000000000' E0 - EF
*
Binary
0 1 2 3 4 5 6 7 8 9
DC
XL16'00010203040506070809000000000000' F0 - FF
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.
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HEXBIN DS
XL4
4 Byte Binary Field.
DS
X
1 Byte Pad for PACK.
HEXDIS DS
CL8
8 Byte Displayable Hex Field.
DS
C
1 Byte Pad for PACK.
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In the above
example, we convert an eight byte displayable hexadecimal field into a
four byte binary field.
Note the extra byte
after the binary and displayable hexadecimal fields. I typically
prefer to convert a word at a time, but you could convert any number of
bytes up to 15 at one time. My recommendation is to stick to
converting words (4 bytes) or double-words (8 bytes) at a time.
I will continue to add
tips and techniques as time permits.
Please direct any
inquiries or problems regarding this web to webmaster@marcsweb.com
Page design, composition and HTML by Marc Niegowski
Copyright © 1998-2012, Marc Niegowski - Connectivity, Inc., All Rights Reserved
23 W. Fourth Street • Media • Pennsylvania • 19063-2805 • USA
Phone: 610-566-0227 • Fax: 610-566-0641 • Email: Marc@Tech-Center.com
Revision Date:
Wednesday, November 15, 2006 10:03:39 AM
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