checksums.superfast: implementation of SuperFastHash.
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John Benediktsson
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SuperFastHash checksum algorithm
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USING: help.markup help.syntax ;
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IN: checksums.superfast
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HELP: superfast
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{ $class-description "SuperFastHash checksum algorithm." } ;
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ARTICLE: "checksums.superfast" "SuperFastHash checksum"
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"SuperFastHash is a hash, created by Paul Hsieh. For more information see: "
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{ $url "http://www.azillionmonkeys.com/qed/hash.html" }
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{ $subsections superfast } ;
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ABOUT: "checksums.superfast"
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USING: checksums fry kernel math sequences tools.test ;
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IN: checksums.superfast
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{
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{
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0
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4064760690
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2484602674
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1021960881
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3514307704
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762925594
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95280079
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516333699
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1761749771
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3841726064
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2549850032
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}
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} [
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"1234567890" [ length 1 + ] keep 0 <superfast>
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'[ _ swap head _ checksum-bytes ] { } map-integers
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] unit-test
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! Copyright (C) 2013 John Benediktsson.
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! See http://factorcode.org/license.txt for BSD license.
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USING: accessors checksums combinators fry grouping io.binary
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kernel math math.bitwise sequences sequences.private ;
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IN: checksums.superfast
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TUPLE: superfast seed ;
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C: <superfast> superfast
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<PRIVATE
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: 32-bit ( n -- n' ) 32 on-bits mask ; inline
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: main-loop ( seq seed -- hash )
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[ 4 <groups> ] dip [
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2 cut-slice
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[ le> + ] [ le> 11 shift dupd bitxor ] bi*
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[ 16 shift ] [ bitxor ] bi* 32-bit
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[ -11 shift ] [ + ] bi
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] reduce ; inline
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: end-case ( hash seq -- hash' )
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dup length {
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[ drop ]
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[
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first + [ 10 shift ] [ bitxor ] bi 32-bit
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[ -1 shift ] [ + ] bi
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]
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[
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le> + [ 11 shift ] [ bitxor ] bi 32-bit
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[ -17 shift ] [ + ] bi
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]
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[
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unclip-last-slice
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[ le> + [ 16 shift ] [ bitxor ] bi ]
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[ 18 shift bitxor ] bi* 32-bit
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[ -11 shift ] [ + ] bi
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]
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} dispatch ; inline
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: avalanche ( hash -- hash' )
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[ 3 shift ] [ bitxor ] bi 32-bit
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[ -5 shift ] [ + ] bi
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[ 4 shift ] [ bitxor ] bi 32-bit
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[ -17 shift ] [ + ] bi
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[ 25 shift ] [ bitxor ] bi 32-bit
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[ -6 shift ] [ + ] bi ; inline
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PRIVATE>
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M: superfast checksum-bytes
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[ dup length 4 mod cut* ] [ seed>> 32-bit ] bi*
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'[ _ main-loop ] [ end-case ] bi* avalanche ;
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