"

 COPYRIGHT (c) 2003 by eXept Software AG

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

"{ Package: 'stx:libbasic2' }"

HashStream subclass:#CRC32Stream

	instanceVariableNames:'crc generatorPolynom crcTable'

	classVariableNames:'CrcTables'

	poolDictionaries:''

	category:'System-Crypt-Hashing'

!

!CRC32Stream class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 2003 by eXept Software AG

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    Standard CRC method as defined by ISO 3309 [ISO-3309] or ITU-T V.42 [ITU-T-V42].

    The default CRC polynomial employed is

	x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1

	(or 16r04C11DB7)

    You can also create an instace performing the Castagnioli CRC-32C

    (used in iSCSI & SCTP, G.hn payload, SSE4.2):

	self newCrc32c

	x32 + x28 + x27 + x26 + x25 + x23 + x22 + x20 + x19 + x18 + x14 + x13 + x11 + x10 + x9 + x8 + x6 + 1

    Only use CRC to protect against communication errors;

    do NOT use CRC for cryptography - use SHA1Stream or MD5Stream instead.

    Notice that this CRC is also used with PNG images - therefore, its performance

    directly affects png image processing.

    throughput:

	157000 Kb/s on a 2.5Ghz 64X2 Athlon 4800+ (64bit)

	150000 Kb/s on 2Ghz Duo

    [author:]

	Stefan Vogel (stefan@zwerg)

    [instance variables:]

    [class variables:]

    [see also:]

	SHA1Stream

	MD5Stream

"

!

examples

"

  expect 60C1D0A0

								[exBegin]

    self information:(CRC32Stream hashValueOf:'resume') hexPrintString

								[exEnd]

  expect 16r60C1D0A0

								[exBegin]

    self information:(CRC32Stream new

			    nextPut:$r;

			    nextPut:$e;

			    nextPut:$s;

			    nextPut:$u;

			    nextPut:$m;

			    nextPut:$e;

			    hashValue) hexPrintString

								[exEnd]

  expect 16r70E46888:

								[exBegin]

    self information:(CRC32Stream hashValueOf:#[1 2 3 4 5 6 7]) hexPrintString

								[exEnd]

  expect 16r8CD04C73:

								[exBegin]

    self information:((CRC32Stream hashValueOf:#[16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF

	     16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF

	     16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF

	     16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF]) hexPrintString)

								[exEnd]

  expect 16r86D7D79A:

  timing throughput:

								[exBegin]

    |hashStream n t|

    hashStream := CRC32Stream new.

    n := 1000000.

    t := Time millisecondsToRun:[

	    n timesRepeat:[

		hashStream nextPutAll:'12345678901234567890123456789012345678901234567890'.

	    ].

	 ].

    t := (t / 1000) asFloat.

    Transcript show:'crc32:'; showCR: hashStream hashValue hexPrintString.

    Transcript show:t; show:' seconds for '; show:(50*n/1024) asFloat; showCR:' Kb'.

    Transcript show:(n*50/1024 / t); showCR:' Kb/s'

								[exEnd]

"

! !

!CRC32Stream class methodsFor:'initialization'!

crcTableFor:generatorPolynomInteger

    |crcTable|

    crcTable := (CrcTables at:generatorPolynomInteger ifAbsent:nil).

    crcTable isNil ifTrue:[

	crcTable := IntegerArray new:256.

	0 to:255 do:[:count| |i|

	    i := count.

	    8 timesRepeat:[

		(i bitTest:1) ifTrue:[

		    i := generatorPolynomInteger bitXor:(i bitShift:-1)

		] ifFalse:[

		    i := i bitShift:-1

		]

	    ].

	    crcTable at:count+1 put:i.

	].

	CrcTables at:generatorPolynomInteger put:crcTable.

    ].

    ^ crcTable.

!

initialize

    CrcTables := Dictionary new.

! !

!CRC32Stream class methodsFor:'instance creation'!

generatorPolynom:anInteger

    ^ self basicNew generatorPolynom:anInteger

    "

       self assert:((self generatorPolynom:16r82F63B78)

				nextPut:'123456789';

				hashValue)    = 16rE3069283

    "

!

newCrc32c

    "return an instance of the Castagnoli CRC-32

	x32 + x28 + x27 + x26 + x25 + x23 + x22 + x20 + x19 + x18 + x14 + x13 + x11 + x10 + x9 + x8 + x6 + 1

     (used in iSCSI & SCTP, G.hn payload, SSE4.2)"

    ^ self basicNew generatorPolynom:16r82F63B78

    "

     Castagnoli crc:

       self assert:((self newCrc32c)

				nextPut:'123456789';

				hashValue) = 3808858755. '16rE3069283'

     default crc:

       self assert:((self new)

				nextPut:'123456789';

				hashValue) = 3421780262. '16rCBF43926'

    "

    "Modified (comment): / 17-05-2012 / 12:48:53 / cg"

! !

!CRC32Stream methodsFor:'accessing'!

generatorPolynom

    "answer the generator polynom"

    ^ generatorPolynom

!

generatorPolynom:anInteger

    "set the generator polynom for this instance.

     Note: you have to set the bit-reversed value, so the LSB must be first"

    generatorPolynom := anInteger.

    crc := 16rFFFFFFFF.

    crcTable := self class crcTableFor:generatorPolynom.

!

reset

    "reset the current crc value"

    crc := 16rFFFFFFFF.

    "Created: / 12-01-2012 / 12:23:03 / cg"

! !

!CRC32Stream methodsFor:'initialization'!

initialize

    "initialize the CRC to CRC-32 ITU-T:

	x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1"

    self generatorPolynom:16rEDB88320

! !

!CRC32Stream methodsFor:'queries'!

hashValue

    "return the computed CRC"

! !

!CRC32Stream methodsFor:'writing'!

nextPutBytes:count from:anObject startingAt:start

    "add the hash of anObject to the computed hash so far."

%{

    if (__bothSmallInteger(count, start)) {

#ifdef __LSBFIRST__

                }

#endif

    }

bad: ;

%}.

    self error:'invalid argument'

    "Created: / 09-01-2012 / 16:48:35 / cg"

! !

!CRC32Stream class methodsFor:'documentation'!

version

!

version_CVS

! !

CRC32Stream initialize!