REBOL [ Title: "gzip" Date: 8-Jan-2013 Version: 1.1.0 File: %gzip.r Author: "Vincent Ecuyer" Purpose: "Creates gzip archives, using the rebol compress command." Usage: { ;REBOL 2: my-data: #{........} write/binary %test.gz gzip/name my-data %my-file.txt ;REBOL 3: my-data: #{........} write %test.gz gzip/name my-data %my-file.txt } Comment: { COMPRESS uses a zlib compatible format - always with deflate algorithm, 32k window size, max compression and no dictionnary - followed by checksum (4 bytes) and uncompressed data length (4 bytes). For REBOL 2.x, this module uses a precalculated crc table, and for REBOL 3.x, it uses the available 'crc32 checksum method. r3 compress/gzip is bugged (wrong checksum), so it isn't used. } History: [ 1.0.0 [1-Jan-2004 "First version"] 1.1.0 [8-Jan-2013 "Now both REBOL 2 and REBOL 3 compatible"] ] Library: [ level: 'advanced platform: 'all type: [module tool] domain: [compression file-handling files] tested-under: [ view 1.2.1.3.1 on [WinXP] view 2.7.8.2.5 on [Macintosh osx-x86] core 2.5.6.2.4 on [Macintosh osx-x86] core 2.7.8.3.1 on [WinXP] core 2.7.8.2.5 on [Macintosh osx-x86] core 2.100.111.2.5 on [Macintosh osx-x86] core 2.101.0.2.5 on [Macintosh osx-x86] ] support: none license: 'public-domain see-also: none ] ] ctx-gzip: 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: func [ "Returns the data crc." data [any-string!] "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-32: func [ "Returns a CRC32 checksum." data [any-string! binary!] "Data to checksum" ] either system/version/2 < 100 [[ either empty? data [#{00000000}][ load join "#{" [to-hex -1 xor update-crc data -1 "}"] ] ]][[ either empty? data [#{00000000}][ copy skip to-binary checksum/method to-binary data 'crc32 4 ] ]] timestamp: func [ "Returns the gzip timestamp." value [date!] "Date to encode." ][ copy/part head reverse do join "#{" [ next mold to-hex (value - 01/01/1970) * 86400 + to-integer value/time - value/zone "}" ] 4 ] set 'gzip func [ "Compresses a string series into a gzip encoding." data [any-string! binary!] "Data to compress" /name "Specifies a filename." file [any-string!] "Filename to use in archive." ][ head change skip tail join #{1F8B08} [ either name [#{08}][#{00}] timestamp now #{02FF} either name [join to-binary file #{00}][#{}] next next compress data ] -8 head reverse crc-32 data ] ]