82 lines
2.9 KiB
Lua
82 lines
2.9 KiB
Lua
--
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-- zip.lua: ZIP archives
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--
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-- Copyright (c) 2017, Přemysl Eric Janouch <p@janouch.name>
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--
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-- Permission to use, copy, modify, and/or distribute this software for any
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-- purpose with or without fee is hereby granted.
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--
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-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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-- SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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-- OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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--
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-- Heuristics required, see https://en.wikipedia.org/wiki/Zip_(file_format)
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local detect = function (c)
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c.endianity = "le"
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for o = #c - 22 + 1, #c - 65535 - 22 + 1, -1 do
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if o < 1 then break end
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c.position = o
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if c:u32 () == 0x06054b50 then return o end
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end
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end
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local decode = function (c)
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local eocd = detect (c ())
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if not eocd then error ("not a ZIP file") end
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c.endianity = "le"
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c.position = eocd
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c:u32 ("end of CD magic: %#x")
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c:u16 ("# of this disk: %d")
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c:u16 ("disk # where CD starts: %d")
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local cd_len = c:u16 ("# of CD records on this disk: %d")
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c:u16 ("total # of CD records: %d")
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c:u32 ("size of CD: %d")
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local cd_offset = c:u32 ("offset of (start of CD - start of archive): %d")
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local comment_len = c:u16 ("comment length: %d")
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c (c.position, c.position + comment_len - 1):mark ("comment")
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-- TODO: decode the fields better
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-- https://stackoverflow.com/a/30028491/76313
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-- TODO: also mark actual file data if someone wants to put in the effort
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c.position = cd_offset + 1
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for i = 1, cd_len do
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local p, magic = c.position, c:u32 ()
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if magic ~= 0x02014b50 then break end
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c (p, c.position - 1):mark ("CD file header magic: %#x", magic)
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c:u16 ("version made by: %d")
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c:u16 ("version needed to extract: %d")
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c:u16 ("general purpose bit flag: %#x")
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c:u16 ("compression method: %d")
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c:u16 ("file last modification time: %d")
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c:u16 ("file last modification date: %d")
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c:u32 ("CRC-32: %#x")
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c:u32 ("compressed size: %d")
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c:u32 ("uncompressed size: %d")
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local filename_len = c:u16 ("file name length: %d")
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local extra_len = c:u16 ("extra field length: %d")
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local comment_len = c:u16 ("file comment length: %d")
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c:u16 ("disk # where file starts: %d")
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c:u16 ("internal file attributes: %#x")
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c:u32 ("external file attributes: %#x")
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c:u32 ("offset of (start of local file header - start of archive): %d")
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c (c.position, c.position + filename_len - 1):mark ("filename")
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c.position = c.position + filename_len
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c (c.position, c.position + extra_len - 1):mark ("extra field")
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c.position = c.position + extra_len
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c (c.position, c.position + comment_len - 1):mark ("file comment")
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c.position = c.position + comment_len
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end
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end
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hex.register { type="zip", detect=detect, decode=decode }
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