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1975
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"{ Package: 'stx:libbasic2' }"
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1192
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HashStream subclass:#CRC32Stream
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instanceVariableNames:'crc'
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classVariableNames:'CrcTable'
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poolDictionaries:''
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category:'System-Crypt-Streams'
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!
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!CRC32Stream class methodsFor:'documentation'!
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documentation
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"
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Standard CRC method as defined by ISO 3309 [ISO-3309] or ITU-T V.42 [ITU-T-V42].
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The CRC polynomial employed is
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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
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Use CRC to protect against communication errors. Do NOT use CRC for cryptography.
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Use SHA1Stream or MD5Stream instead.
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[author:]
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Stefan Vogel (stefan@zwerg)
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[instance variables:]
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[class variables:]
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[see also:]
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SHA1Stream
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MD5Stream
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"
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!
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examples
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"
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[exBegin]
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self information:(CRC32Stream hashValueOf:'Dies ist ein Test') printString
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1975
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CRC32Stream [exEnd]
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1192
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[exBegin]
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self information:(CRC32Stream new nextPut:4711; hashValue) printString
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1975
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CRC32Stream [exEnd]
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1192
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[exBegin]
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self information:(CRC32Stream hashValueOf:#[1 2 3 4 5 6 7]) printString
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[exEnd]
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[exBegin]
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self information:((CRC32Stream hashValueOf:#[16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF
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16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF
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16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF
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1975
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16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF]) digitBytes hexPrintString)
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1192
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[exEnd]
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"
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! !
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!CRC32Stream class methodsFor:'initialization'!
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initialize
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CrcTable := IntegerArray new:256.
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0 to:255 do:[:count| |i|
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i := count.
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8 timesRepeat:[
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(i bitTest:1) ifTrue:[
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i := 16rEDB88320 bitXor:(i bitShift:-1)
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] ifFalse:[
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i := i bitShift:-1
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]
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].
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CrcTable at:count+1 put:i.
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].
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"
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self initialize
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"
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! !
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!CRC32Stream class methodsFor:'testing'!
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testVector
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"define a testvector to test the implementation"
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^ #(
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(#[16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF
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16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF
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16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF
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16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF 16rFF]
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2362461299)
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(#[0 0 0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0 0 0]
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3924573617)
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(#[0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
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20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39]
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228994620 )
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)
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"
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self test
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"
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! !
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!CRC32Stream methodsFor:'initialization'!
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initialize
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"initialize the CRC"
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crc := 16rFFFFFFFF.
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! !
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!CRC32Stream methodsFor:'queries'!
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hashValue
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"return the computed CRC"
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^ crc bitXor:16rFFFFFFFF
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! !
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!CRC32Stream methodsFor:'writing'!
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nextPut:arg
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"add the hash of anObject to the computed hash so far.
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anObject can be a Character, SmallInteger, or Character-, Byte-
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Integer-Array"
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arg isCharacter ifTrue:[
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crc := (CrcTable at:((crc bitXor:arg asciiValue) bitAnd:16rFF)+1)
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bitXor:(crc bitShift:-8).
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^ self.
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].
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arg isInteger ifTrue:[
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arg < 256 ifTrue:[
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crc := (CrcTable at:((crc bitXor:arg) bitAnd:16rFF)+1)
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bitXor:(crc bitShift:-8).
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^ self.
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].
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arg digitBytes do:[:byte|
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crc := (CrcTable at:((crc bitXor:byte) bitAnd:16rFF)+1)
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bitXor:(crc bitShift:-8).
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].
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^ self.
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].
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arg isCollection ifTrue:[
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arg do:[:element|
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self nextPut:element
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].
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^ self.
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].
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self error:'unsupported argument'.
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! !
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!CRC32Stream class methodsFor:'documentation'!
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version
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1975
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^ '$Header: /cvs/stx/stx/libbasic2/CRC32Stream.st,v 1.2 2008-04-24 14:18:30 stefan Exp $'
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! !
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CRC32Stream initialize!
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