FEAT: simple GZIP codec

Author: Oldes

src/mezz/boot-files.r

@@ -51,6 +51,7 @@ REBOL [
 	%codec-wav.r
 	%codec-der.r
 	%codec-crt.r
+	%codec-gzip.r
 ]
 
 ;-- protocols:

src/mezz/codec-gzip.r

@@ -0,0 +1,75 @@
+REBOL [
+	title: "REBOL 3 coded lossless compressed data format compatible with GZIP utility."
+	name: 'codec-gzip
+	author: rights: "Oldes"
+	version: 0.0.1
+	specification: https://tools.ietf.org/html/rfc1952
+]
+
+register-codec [
+	name:  'GZIP
+	title: "Lossless compressed data format compatible with GZIP utility."
+	suffixes: [%.gz]
+	decode: function[data [binary!]] [
+		if verbose > 0 [ identify data ]
+		decompress/gzip data
+	]
+
+	encode: function [data [binary!]][
+		compress/gzip/level data level
+	]
+
+	identify: function [data [binary!]][
+		if verbose > 0 [
+			print ["^[[1;32mDecode GZIP data^[[m (^[[1m" length? data "^[[mbytes )"]
+		]
+		bin: binary data
+		binary/read bin [
+			id:    UI16   ; Magick: #{1F8B}
+			cm:    UI8    ; Compression Method
+			flg:   UI8    ; FLaGs
+			mtime: UI32LE ; Modification TIME
+			xfl:   UI8    ; eXtra FLags
+			os:    UI8    ; Operating System
+		]
+		if any [
+			id <> 8075 ;- not GZIP magick number
+			cm <> 8    ;- unsupported compression
+		][ return none ] 
+
+		mtime: either mtime > 0 [ 1-1-1970 + to time! mtime ][ none ]
+
+		if 4 = (4 and flg) [ ;FEXTRA
+			extra: binary/read bin 'UI16LEBYTES
+		]
+		if 8 = (8 and flg) [ ;FNAME
+			name: to file! binary/read bin 'STRING ; zero terminated
+		]
+		if 16 = (16 and flg) [ ;FCOMMENT
+			comm: to file! binary/read bin 'STRING ; zero terminated
+		]
+		if 2 = (2 and flg) [ ;FHCRC
+			;the two least significant bytes of the CRC32 for all bytes of the gzip header up to and not including the CRC16
+			;checksum/method/part bin/buffer-write 'CRC32 index? bin/buffer
+			crc16: binary/read bin 'UI16LE
+		]
+		if verbose > 0 [	
+			print ["^[[32mModified:         ^[[0;1m" mtime "^[[m"]
+			print ["^[[32mExtra flags:      ^[[0;1m" xfl "^[[m"]
+			print ["^[[32mOperating system: ^[[0;1m" os "^[[m"]
+			print ["^[[32mExtra field:      ^[[0;1m" extra "^[[m"]
+			print ["^[[32mFile name:        ^[[0;1m" name "^[[m"]
+			print ["^[[32mHeader CRC:       ^[[0;1m" crc16 "^[[m"]
+		]
+		compose [
+			file:        (all [name  to file! name])
+			modified:    (mtime)
+			os:          (os)
+			extra-flags: (xfl)
+			extra-data:  (extra)
+		]
+	]
+
+	verbose: 1
+	level: 9
+]

src/tests/units/compress-test.r3

@@ -70,6 +70,14 @@ data: "test test test"
 		--assert  #{74657374} = decompress/gzip compress/gzip/part data 4
 		--assert  #{74657374} = decompress/gzip compress/gzip/part skip data 5 4
 		--assert  #{74657374} = decompress/gzip compress/gzip/part tail data -4
+
+	--test-- "GZIP codec"
+		--assert  binary? alice: load %units/files/alice29.txt.gz
+		--assert  #{37A087D23C8709E97AA45ECE662FAF3D07006A58} = checksum/method alice 'sha1
+		--assert  port? save %units/files/tmp.gz alice
+		--assert  binary? alice: load %units/files/tmp.gz
+		--assert  #{37A087D23C8709E97AA45ECE662FAF3D07006A58} = checksum/method alice 'sha1
+		delete %units/files/tmp.gz
 
 ===end-group===