2017-05-21 21:08:33 +02:00
|
|
|
--
|
|
|
|
|
-- zlib.lua: ZLIB Compressed Data 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.
|
|
|
|
|
--
|
|
|
|
|
|
|
|
|
|
-- Based on RFC 1950, this format isn't very widely used
|
|
|
|
|
local decode = function (c)
|
2017-05-29 15:47:05 +02:00
|
|
|
c.endianity = 'le'
|
2017-05-21 21:08:33 +02:00
|
|
|
|
|
|
|
|
local deflate_levels = { "fastest", "fast", "default", "slowest" }
|
|
|
|
|
local deflate
|
|
|
|
|
local cmf = c:u8 ("compression method and flags: %s", function (u8)
|
|
|
|
|
local cm, cm_name = u8 & 0xf, "unknown"
|
|
|
|
|
local cinfo, cinfo_name = u8 >> 4, "unknown"
|
|
|
|
|
if cm == 8 then
|
|
|
|
|
deflate = true
|
|
|
|
|
cm_name = "deflate"
|
|
|
|
|
cinfo_name = ("window size = %d"):format (2 ^ (cinfo + 8))
|
|
|
|
|
end
|
|
|
|
|
return "%s (%d), %s (%d)", cm_name, cm, cinfo_name, cinfo
|
|
|
|
|
end)
|
|
|
|
|
local have_dict
|
|
|
|
|
local flags = c:u8 ("flags: %s", function (u8)
|
|
|
|
|
local check = (cmf * 256 + u8) % 31 == 0
|
|
|
|
|
if check then check = "ok" else check = "failed" end
|
|
|
|
|
|
|
|
|
|
local level, level_name = (u8 >> 6) & 3, "unknown"
|
|
|
|
|
if deflate then level_name = deflate_levels[level + 1] end
|
|
|
|
|
have_dict = (u8 >> 5) & 1 == 1
|
|
|
|
|
|
|
|
|
|
local info = "preset dictionary"
|
|
|
|
|
if not have_dict then info = "no " .. info end
|
|
|
|
|
return "level %s (%d), check %s, %s", level_name, level, check, info
|
|
|
|
|
end)
|
|
|
|
|
if have_dict then
|
|
|
|
|
c:u16 ("dictionary Adler-32 checksum: %04x")
|
|
|
|
|
end
|
|
|
|
|
|
|
|
|
|
-- Compressed data follows immediately
|
|
|
|
|
-- Not going to decompress it, so we don't know where the final checksum is
|
|
|
|
|
end
|
|
|
|
|
|
|
|
|
|
hex.register { type="zlib", detect=nil, decode=decode }
|
