OC-PsychOS2/lib/libmtar.lua

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local mtar = {}
local versions = {}
versions[0] = {nlf = ">I2", flf = ">I2"} -- original version format
versions[1] = {nlf = ">I2", flf = ">I8"} -- extended file size format
mtar.versions = versions
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local function cleanPath(path)
local pt = {}
for segment in path:gmatch("[^/]+") do
if segment == ".." then
pt[#pt] = nil
elseif segment ~= "." then
pt[#pt+1] = segment
end
end
return table.concat(pt,"/")
end
function mtar.genHeader(fname,len,version) -- string number -- string -- generate a header for file *fname* when provided with file length *len*
version=version or 1
return string.format("\255\255%s%s%s%s", string.char(version), string.pack(versions[version].nlf,fname:len()), fname, string.pack(versions[version].flf,len))
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end
function mtar.iter(stream) -- table -- function -- Given buffer *stream*, returns an iterator suitable for use with *for* that returns, for each iteration, the file name, a function to read from the file, and the length of the file.
local remain = 0
local function read(n)
local rb = stream:read(math.min(n,remain))
remain = remain - rb:len()
return rb
end
return function()
while remain > 0 do
remain=remain-#stream:read(math.min(remain,2048))
end
local version = 0
local nlen = string.unpack(">I2", stream:read(2) or "\0\0")
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if nlen == 0 then
return
elseif nlen == 65535 then -- versioned header
version = string.byte(stream:read(1))
nlen = string.unpack(versions[version].nlf, stream:read(string.packsize(versions[version].nlf)))
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end
local name = cleanPath(stream:read(nlen))
remain = string.unpack(versions[version].flf, stream:read(string.packsize(versions[version].flf)))
return name, read, remain
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end
end
return mtar