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2016 Update

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Tina Müller 2016-12-05 22:15:40 +01:00
parent 948b86eafa
commit dcf5d15da3
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Task/CRC-32/REXX/crc-32.rexx
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@ -1,37 +1,34 @@
/*REXX program computes the CRC─32 (32 bit Cyclic Redundancy Check) checksum*/
/*─────────────────for a given string [as described in ISO 3309, ITU─T V.42].*/
/*REXX program computes the CRC─32 (32 bit Cyclic Redundancy Check) checksum for a */
/*─────────────────────────────────given string [as described in ISO 3309, ITU─T V.42].*/
call show 'The quick brown fox jumps over the lazy dog' /*the 1st string.*/
call show 'Generate CRC32 Checksum For Byte Array Example' /* " 2nd " */
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
CRC_32: procedure; parse arg !,$; c='edb88320'x /*2nd arg used for repeated invocations*/
f='ffFFffFF'x /* [↓] build an 8─bit indexed table,*/
do i=0 for 256; z=d2c(i) /* one byte at a time.*/
r=right(z, 4, '0'x) /*insure the "R" is thirty-two bits.*/
/* [↓] handle each rightmost byte bit.*/
do j=0 for 8; rb=x2b(c2x(r)) /*handle each bit of rightmost 8 bits. */
r=x2c(b2x(0 || left(rb, 31))) /*shift it right (an unsigned) 1 bit.*/
if right(rb,1) then r=bitxor(r,c) /*this is a bin bit for XOR grunt─work.*/
end /*j*/
!.z=r /*assign to an eight─bit index table. */
end /*i*/
call show 'The quick brown fox jumps over the lazy dog' /*1st string.*/
call show 'Generate CRC32 Checksum For Byte Array Example' /*2nd " */
exit /*stick a fork in it, we're all done. */
/*────────────────────────────────────────────────────────────────────────────*/
CRC_32: procedure; parse arg !,$ /*2nd arg: it has repeated─invocations.*/
/* [↓] build an 8─bit indexed table,*/
do i=0 for 256; z=d2c(i) /* one byte at a time.*/
r=right(z, 4, '0'x) /*insure the "R" is thirty-two bits.*/
do j=0 for 8 /*handle each bit of rightmost 8 bits. */
rb=x2b(c2x(r)) /*convert character ──► hex ──► binary.*/
_=right(rb,1) /*remember the right─most bit for IF. */
r=x2c(b2x(0 || left(rb, 31))) /*shift it right (an unsigned) 1 bit.*/
if _\==0 then r=bitxor(r, 'edb88320'x) /*this is bit XOR grunt─work.*/
end /*j*/
!.z=r /*assign to an eight─bit index table. */
end /*i*/
$=bitxor(word($ '0000000'x,1),'ffFFffFF'x) /*use the user's CRC or a default.*/
do k=1 for length(!) /*start crunching the input data. */
?=bitxor(right($, 1), substr(!, k, 1))
$=bitxor('0'x || left($, 3), !.?)
end /*k*/
return $ /*return with da money to the invoker. */
/*────────────────────────────────────────────────────────────────────────────*/
show: procedure; parse arg Xstring; numeric digits 12; say; say
checksum=CRC_32(Xstring) /*invoke CRC_32 to create a CRC.*/
checksum=bitxor(checksum,'ffFFffFF'x) /*final convolution for checksum.*/
say center(' input string [length of' length(Xstring) "bytes] ", 79, '═')
say Xstring /*show the string on its own line*/
say /*↓↓↓↓↓↓↓↓↓↓↓↓ is fifteen blanks*/
say 'hex CRC-32 checksum =' c2x(checksum) left('', 15),
"dec CRC-32 checksum =" c2d(checksum) /*show the CRC-32 in hex and dec.*/
return
$=bitxor(word($ '0000000'x, 1), f) /*utilize the user's CRC or a default. */
do k=1 for length(!) /*start number crunching the input data*/
?=bitxor(right($,1), substr(!,k,1))
$=bitxor('0'x || left($, 3), !.?)
end /*k*/
return $ /*return with cyclic redundancy check. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
show: procedure; parse arg Xstring; numeric digits 12; say; say
checksum=CRC_32(Xstring) /*invoke CRC_32 to create a CRC.*/
checksum=bitxor(checksum, 'ffFFffFF'x) /*final convolution for checksum.*/
say center(' input string [length of' length(Xstring) "bytes] ", 79, '═')
say Xstring /*show the string on its own line*/
say /*↓↓↓↓↓↓↓↓↓↓↓↓ is fifteen blanks*/
say "hex CRC-32 checksum =" c2x(checksum) left('', 15),
"dec CRC-32 checksum =" c2d(checksum) /*show the CRC-32 in hex and dec.*/
return