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-- create module namespace
ltn12 = ltn12 or {}
-- make all globals fall into ltn12 namespace
setmetatable(ltn12, { __index = _G })
setfenv(1, ltn12)
-- sub namespaces
filter = {}
source = {}
sink = {}
-- 2048 seems to be better in windows...
BLOCKSIZE = 2048
local function second(a, b)
return b
end
local function skip(a, b, c)
return b, c
end
-- returns a high level filter that cycles a cycles a low-level filter
function filter.cycle(low, ctx, extra)
return function(chunk)
local ret
ret, ctx = low(ctx, chunk, extra)
return ret
end
end
-- chains two filters together
local function chain2(f1, f2)
return function(chunk)
return f2(f1(chunk))
end
end
-- chains a bunch of filters together
function filter.chain(...)
local f = arg[1]
for i = 2, table.getn(arg) do
f = chain2(f, arg[i])
end
return f
end
-- create an empty source
function source.empty(err)
return function()
return nil, err
end
end
-- creates a file source
function source.file(handle, io_err)
if handle then
return function()
local chunk = handle:read(BLOCKSIZE)
if not chunk then handle:close() end
return chunk
end
else source.empty(io_err or "unable to open file") end
end
-- turns a fancy source into a simple source
function source.simplify(src)
return function()
local chunk, err_or_new = src()
src = err_or_new or src
if not chunk then return nil, err_or_new
else return chunk end
end
end
-- creates string source
function source.string(s)
if s then
local i = 1
return function()
local chunk = string.sub(s, i, i+BLOCKSIZE-1)
i = i + BLOCKSIZE
if chunk ~= "" then return chunk
else return nil end
end
else source.empty() end
end
-- creates rewindable source
function source.rewind(src)
local t = {}
return function(chunk)
if not chunk then
chunk = table.remove(t)
if not chunk then return src()
else return chunk end
else
table.insert(t, chunk)
end
end
end
-- chains a source with a filter
function source.chain(src, f)
local co = coroutine.create(function()
while true do
local chunk, err = src()
local filtered = f(chunk)
local done = chunk and ""
while true do
coroutine.yield(filtered)
if filtered == done then break end
filtered = f(done)
end
if not chunk then return nil, err end
end
end)
return function()
return skip(coroutine.resume(co))
end
end
-- creates a source that produces contents of several files one after the
-- other, as if they were concatenated
function source.cat(...)
local co = coroutine.create(function()
local i = 1
while i <= table.getn(arg) do
local chunk = arg[i]:read(2048)
if chunk then coroutine.yield(chunk)
else i = i + 1 end
end
end)
return source.simplify(function()
return second(coroutine.resume(co))
end)
end
-- creates a sink that stores into a table
function sink.table(t)
t = t or {}
local f = function(chunk, err)
if chunk then table.insert(t, chunk) end
return 1
end
return f, t
end
-- turns a fancy sink into a simple sink
function sink.simplify(snk)
return function(chunk, err)
local ret, err_or_new = snk(chunk, err)
if not ret then return nil, err_or_new end
snk = err_or_new or snk
return 1
end
end
-- creates a file sink
function sink.file(handle, io_err)
if handle then
return function(chunk, err)
if not chunk then
handle:close()
return nil, err
end
return handle:write(chunk)
end
else sink.null() end
end
-- creates a sink that discards data
local function null()
return 1
end
function sink.null()
return null
end
-- chains a sink with a filter
function sink.chain(f, snk)
return function(chunk, err)
local filtered = f(chunk)
local done = chunk and ""
while true do
local ret, snkerr = snk(filtered, err)
if not ret then return nil, snkerr end
if filtered == done then return 1 end
filtered = f(done)
end
end
end
-- pumps all data from a source to a sink
function pump(src, snk)
while true do
local chunk, src_err = src()
local ret, snk_err = snk(chunk, src_err)
if not chunk or not ret then
return not src_err and not snk_err, src_err or snk_err
end
end
end
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