55 lines
2.2 KiB
Lua
55 lines
2.2 KiB
Lua
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-- A collection of pipe-based utility functions
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-- A convenience wrapper for chunking data arriving in bursts into more sizable
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-- blocks; `o` will be called once per chunk. The `flush` method can be used to
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-- drain the internal buffer. `flush` MUST be called at the end of the stream,
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-- **even if the stream is a multiple of the chunk size** due to internal
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-- buffering. Flushing results in smaller chunk(s) being output, of course.
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local function chunker(o, csize, prio)
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assert (type(o) == "function" and type(csize) == "number" and 1 <= csize)
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local p = pipe.create(function(p)
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-- wait until it looks very likely that read is going to succeed
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-- and we won't have to unread. This may hold slightly more than
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-- a chunk in the underlying pipe object.
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if 256 * (p:nrec() - 1) <= csize then return nil end
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local d = p:read(csize)
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if #d < csize
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then p:unread(d) return false
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else o(d) return true
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end
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end, prio or node.task.LOW_PRIORITY)
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return {
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flush = function() for d in p:reader(csize) do o(d) end end,
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write = function(d) p:write(d) end
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}
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end
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-- Stream and decode lines of complete base64 blocks, calling `o(data)` with
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-- decoded chunks or calling `e(badinput, errorstr)` on error; the error
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-- callback must ensure that this conduit is never written to again.
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local function debase64(o, e, prio)
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assert (type(o) == "function" and type(e) == "function")
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local p = pipe.create(function(p)
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local s = p:read("\n+")
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if s:sub(-1) == "\n" then -- guard against incomplete line
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s = s:match("^%s*(%S*)%s*$")
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if #s ~= 0 then -- guard against empty line
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local ok, d = pcall(encoder.fromBase64, s)
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if ok then o(d) else e(s, d); return false end
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end
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return true
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else
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p:unread(s)
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return false
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end
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end, prio or node.task.LOW_PRIORITY)
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return { write = function(d) p:write(d) end }
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end
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return {
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chunker = chunker,
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debase64 = debase64,
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}
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