1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
--
-- gzip.lua: GZIP File Format
--
-- Copyright (c) 2017, Přemysl Janouch <p.janouch@gmail.com>
--
-- Permission to use, copy, modify, and/or distribute this software for any
-- purpose with or without fee is hereby granted, provided that the above
-- copyright notice and this permission notice appear in all copies.
--
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
-- SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
-- OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
--
local detect = function (c)
return c:read (2) == "\x1f\x8b"
end
local function latin1_to_utf8 (s)
local u = ""
for _, c in ipairs (table.pack (s:byte (1, #s))) do
if c < 0x80 then
u = u .. string.char (c)
else
u = u .. string.char (0xc0 | c >> 6, 0x80 | c & 0x3f)
end
end
return u
end
-- Everything here is based on RFC 1952 and some bits of dictzip
local crc32_table = function ()
local table = {}
for n = 0, 255 do
local c = n
for k = 0, 7 do
if c & 1 ~= 0 then
c = 0xedb88320 ~ (c >> 1)
else
c = c >> 1
end
end
table[n] = c
end
return table
end
local crc32 = function (s)
local table, c = crc32_table (), 0xffffffff
for n = 1, #s do c = table[(c ~ s:byte (n)) & 0xff] ~ (c >> 8) end
return c ~ 0xffffffff
end
local os_table = {
[0] = "FAT filesystem",
[1] = "Amiga",
[2] = "VMS",
[3] = "Unix",
[4] = "VM/CMS",
[5] = "Atari TOS",
[6] = "HPFS filesystem",
[7] = "Macintosh",
[8] = "Z-System",
[9] = "CP/M",
[10] = "TOPS-20",
[11] = "NTFS filesystem",
[12] = "QDOS",
[13] = "Acord RISCOS",
[255] = "unknown"
}
local decode = function (c)
if not detect (c ()) then error ("not a GZIP file") end
local start = c.position
c.endianity = 'le'
c:u16 ("GZIP magic")
local deflate
c:u8 ("compression method: %s", function (u8)
if u8 ~= 8 then return "unknown: %d", u8 end
deflate = true
return "deflate"
end)
local text, hcrc, extra, name, comment
c:u8 ("flags: %s", function (u8)
text = u8 & 1 == 1
hcrc = (u8 >> 1) & 1 == 1
extra = (u8 >> 2) & 1 == 1
name = (u8 >> 3) & 1 == 1
comment = (u8 >> 4) & 1 == 1
local flags = ""
if text then flags = flags .. ", text" end
if hcrc then flags = flags .. ", header CRC" end
if extra then flags = flags .. ", extra" end
if name then flags = flags .. ", filename" end
if comment then flags = flags .. ", comment" end
if flags == "" then
return "none"
else
return "%s", flags:sub (3)
end
end)
c:u32 ("modified time: %s", function (u32)
if u32 == 0 then return "none" end
return os.date ("!%F %T", u32)
end)
c:u8 ("extra flags: %s", function (u8)
if deflate then
if u8 == 2 then return "slowest (%d)", u8 end
if u8 == 4 then return "fastest (%d)", u8 end
end
return "unknown: %d", u8
end)
c:u8 ("OS: %s", function (u8)
local os = os_table[u8]
if os then return os end
return "unknown: %d", u8
end)
local extra_table = {}
if extra then
local len = c:u16 ("extra field length: %d")
c (c.position, c.position + len - 1):mark ("extra field")
-- This will handle even overflowing subfields
while len >= 4 do
local p, sid = c.position, c:read (2)
c (p, c.position - 1):mark ("subfield ID: %s", sid)
local sid_len = c:u16 ("subfield length: %d")
local subfield = c (c.position, c.position + sid_len - 1)
subfield:mark ("subfield data")
extra_table[sid] = subfield
c.position = c.position + sid_len
len = len - 4 - sid_len
end
c.position = c.position + len
end
if name then
c:cstring ("filename: %s", latin1_to_utf8)
end
if comment then
c:cstring ("comment: %s", latin1_to_utf8)
end
if hcrc then
c:u16 ("CRC-16: %s", function (u16)
local crc = 0xffff & crc32 (c (start):read (c.position - 1))
if crc == u16 then check = "ok" else check = "failed" end
return "%#06x (%s)", u16, check
end)
end
-- Compressed data follows immediately
-- We can jump through it without decompression in dictzip v1 archives
local ra = extra_table["RA"]
if not ra then return end
local ra_ver = ra:u16 ("RA version: %d")
if ra_ver ~= 1 then return end
local ra_chunk = ra:u16 ("chunk length: %d")
local ra_count = ra:u16 ("chunk count: %d")
for i = 1, ra_count do
local len = ra:u16 ("chunk " .. i .. " compressed length: %d")
c (c.position, c.position + len - 1):mark ("chunk " .. i)
c.position = c.position + len
end
-- 1 final, 01 static, 0000000 end of block, padding discarded
-- This is the kind of block that dictzip finalizes archives with
if c:u16 () & 0x03ff == 0x0003 then
c:u32 ("CRC-32: %#010x")
c:u32 ("input size: %d")
end
end
hex.register { type="gzip", detect=detect, decode=decode }
|