42 lines
917 B
Factor
42 lines
917 B
Factor
! Copyright (C) 2006 Doug Coleman
|
|
! See http://factorcode.org/license.txt for BSD license.
|
|
USING: kernel math sequences sequences.private namespaces
|
|
words io io.binary io.files quotations
|
|
definitions checksums ;
|
|
IN: checksums.crc32
|
|
|
|
CONSTANT: crc32-polynomial HEX: edb88320
|
|
|
|
CONSTANT: crc32-table V{ }
|
|
|
|
256 iota [
|
|
8 [
|
|
[ 2/ ] [ even? ] bi [ crc32-polynomial bitxor ] unless
|
|
] times
|
|
] map 0 crc32-table copy
|
|
|
|
: (crc32) ( crc ch -- crc )
|
|
dupd bitxor
|
|
mask-byte crc32-table nth-unsafe
|
|
swap -8 shift bitxor ; inline
|
|
|
|
SINGLETON: crc32
|
|
|
|
INSTANCE: crc32 checksum
|
|
|
|
: init-crc32 ( input checksum -- x y input )
|
|
drop [ HEX: ffffffff dup ] dip ; inline
|
|
|
|
: finish-crc32 ( x y -- bytes )
|
|
bitxor 4 >be ; inline
|
|
|
|
M: crc32 checksum-bytes
|
|
init-crc32
|
|
[ (crc32) ] each
|
|
finish-crc32 ;
|
|
|
|
M: crc32 checksum-lines
|
|
init-crc32
|
|
[ [ (crc32) ] each CHAR: \n (crc32) ] each
|
|
finish-crc32 ;
|