REBOL [ Title: "CRC-32" Date: 30-Jan-2013 Version: 1.2.0 Type: module File: %crc32.r Exports: [crc-32] Author: "Vincent Ecuyer" Purpose: "CRC32 checksum function" Usage: { Calculates a 32 bits cyclic redundancy code as used in gzip/pkzip/etc. Returns a binary: >> crc-32 "a string" == #{99A255DA} >> crc-32 #{112233445566} == #{345913D6} or an integer: >> crc-32/integer "a string" == -1717414438 To compute the checksum part by part: >> crc-32 "a str" == #{61AD7C35} >> crc-32/continue "ing" #{61AD7C35} == #{99A255DA} >> crc-32/continue data none is a synonym of: >> crc-32 data Usage of /continue in a loop: ; initial crc crc: none until [ ... ; a new crc is computed from the previous one and the new data crc: crc-32/continue data-part crc ... ] ; at the end of this loop, 'crc holds the crc-32 of the whole data The /direct mode, with a specified buffer size, works directly on files (useful for big files): ; calculates the checksum of a remote file with a 64 kb buffer >> crc-32/direct ftp://192.168.1.33/rebol.exe 64 * 1024 == #{67AD9CF6} Note: In the case of a file access error, connection timeout, or an execution halted by the user, the opened file can still be locked. Any new invocation of 'crc-32 will release (close) the file and clear the internal buffer. Example: >> crc-32 "" } Comment: { Contains a precalculated table for speedup. REBOL VM isn't really suited for fast bitwise operations, so this code is quite slow. If the rebcode VM is available, it's used to achieve a more usable speed (between checksum/method 'md5 and checksum/method 'sha1). } Library: [ level: 'advanced platform: 'all type: [module function rebcode] domain: [math security] tested-under: [ core 2.101.0.2.5 on [Macintosh osx-x86] view 2.7.8.2.5 on [Macintosh osx-x86] core 2.6.2.3.1 on [Win2K] view 1.3.2.3.1 on [Win2K] view 1.3.61.3.1 on [Win2K] base 2.5.4.3.1 on [Win2K] view 1.2.1.1.1 on [AmigaOS30] core 2.5.0.1.1 on [AmigaOS30] ] support: none license: 'bsd see-also: %rebzip.r ] History: [ 1.2.0 30-Jan-2013 "r3 compatibility and module declaration" 1.1.0 6-Apr-2006 "/direct mode, /continue and /integer added" 1.0.0 26-Mar-2006 "First published version" ] ] ctx-crc-32: context [ crc-long: [ 0 1996959894 -301047508 -1727442502 124634137 1886057615 -379345611 -1637575261 249268274 2044508324 -522852066 -1747789432 162941995 2125561021 -407360249 -1866523247 498536548 1789927666 -205950648 -2067906082 450548861 1843258603 -187386543 -2083289657 325883990 1684777152 -43845254 -1973040660 335633487 1661365465 -99664541 -1928851979 997073096 1281953886 -715111964 -1570279054 1006888145 1258607687 -770865667 -1526024853 901097722 1119000684 -608450090 -1396901568 853044451 1172266101 -589951537 -1412350631 651767980 1373503546 -925412992 -1076862698 565507253 1454621731 -809855591 -1195530993 671266974 1594198024 -972236366 -1324619484 795835527 1483230225 -1050600021 -1234817731 1994146192 31158534 -1731059524 -271249366 1907459465 112637215 -1614814043 -390540237 2013776290 251722036 -1777751922 -519137256 2137656763 141376813 -1855689577 -429695999 1802195444 476864866 -2056965928 -228458418 1812370925 453092731 -2113342271 -183516073 1706088902 314042704 -1950435094 -54949764 1658658271 366619977 -1932296973 -69972891 1303535960 984961486 -1547960204 -725929758 1256170817 1037604311 -1529756563 -740887301 1131014506 879679996 -1385723834 -631195440 1141124467 855842277 -1442165665 -586318647 1342533948 654459306 -1106571248 -921952122 1466479909 544179635 -1184443383 -832445281 1591671054 702138776 -1328506846 -942167884 1504918807 783551873 -1212326853 -1061524307 -306674912 -1698712650 62317068 1957810842 -355121351 -1647151185 81470997 1943803523 -480048366 -1805370492 225274430 2053790376 -468791541 -1828061283 167816743 2097651377 -267414716 -2029476910 503444072 1762050814 -144550051 -2140837941 426522225 1852507879 -19653770 -1982649376 282753626 1742555852 -105259153 -1900089351 397917763 1622183637 -690576408 -1580100738 953729732 1340076626 -776247311 -1497606297 1068828381 1219638859 -670225446 -1358292148 906185462 1090812512 -547295293 -1469587627 829329135 1181335161 -882789492 -1134132454 628085408 1382605366 -871598187 -1156888829 570562233 1426400815 -977650754 -1296233688 733239954 1555261956 -1026031705 -1244606671 752459403 1541320221 -1687895376 -328994266 1969922972 40735498 -1677130071 -351390145 1913087877 83908371 -1782625662 -491226604 2075208622 213261112 -1831694693 -438977011 2094854071 198958881 -2032938284 -237706686 1759359992 534414190 -2118248755 -155638181 1873836001 414664567 -2012718362 -15766928 1711684554 285281116 -1889165569 -127750551 1634467795 376229701 -1609899400 -686959890 1308918612 956543938 -1486412191 -799009033 1231636301 1047427035 -1362007478 -640263460 1088359270 936918000 -1447252397 -558129467 1202900863 817233897 -1111625188 -893730166 1404277552 615818150 -1160759803 -841546093 1423857449 601450431 -1285129682 -1000256840 1567103746 711928724 -1274298825 -1022587231 1510334235 755167117 ] right-shift-8: func [ "Right-shifts the value by 8 bits and returns it." value [integer!] "The value to shift" ][ either negative? value [ -1 xor value and -256 / 256 xor -1 and 16777215 ][ -256 and value / 256 ] ] update-crc: either value? 'rebcode [ rebcode [ "Returns the data crc." data [any-string! binary!] "Data to checksum" crc [integer!] "Initial value" /local char i ][ tail? data iff [ until [ pick char data 1 set.i i crc xor i char and i 255 lsr crc 8 pickz i crc-long i xor crc i next data tail? data ] ] return crc ] ][ func [ "Returns the data crc." data [any-string! binary!] "Data to checksum" crc [integer!] "Initial value" ][ foreach char data [ crc: (right-shift-8 crc) xor pick crc-long crc and 255 xor char + 1 ] crc ] ] any-file?: func [ "Returns TRUE for file and url values." value [any-type!] ][any [file? value url? value]] file: none buffer: none set 'crc-32 func [ "Returns a CRC32 checksum." source [binary! string! file! url!] "Data or file to checksum" /direct "For file! and url! sources, uses /direct mode" buffer-size [integer!] "Buffer size (in bytes)" /integer "Returns an integer! instead of a binary!" /continue "Continues a checksum with more data" crc [integer! binary! none!] "Previous CRC32 value." ][ crc: -1 xor to-integer any [crc 0] if file [error? try [close file ] file: none] if buffer [error? try [clear buffer] buffer: none] either all [direct any-file? source system/version < 2.100.0] [ file: source: open/direct/read/binary source buffer: make binary! buffer-size until [ clear buffer read-io source buffer buffer-size crc: update-crc buffer crc wait 0.002 zero? length? buffer ] clear buffer close source buffer: file: source: none ][ if any-file? source [ source: either system/version < 2.100.0 [ read/binary source ][ read source ] ] if string? source [source: to-binary source] either any [continue system/version < 2.100.0] [ crc: update-crc source crc ][ crc: -1 xor checksum/method source 'crc32 ] source: none ] either integer [-1 xor crc][ copy at tail load join "#{" [next mold to-hex -1 xor crc "}"] -4 ] ] ] ; Verification either #{CBF43926} <> crc-32 "123456789" [ make error! "Test failed - CRC-32 doesn't work with this VM." ][true]