55 lines
1.7 KiB
Lua
55 lines
1.7 KiB
Lua
--[[
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Licensed according to the included 'LICENSE' document
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Author: Thomas Harning Jr <harningt@gmail.com>
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]]
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local setmetatable = setmetatable
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local assert, loadstring = assert, loadstring or load
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local _ENV = nil
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-- Key == weak, if main key goes away, then cache cleared
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local outputCache = setmetatable({}, {__mode = 'k'})
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-- TODO: inner tables weak?
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local function buildFunction(nextValues, innerValue, valueWriter, innerWriter)
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local putInner = ""
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if innerValue and innerWriter then
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-- Prepare the lua-string representation of the separator to put in between values
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local formattedInnerValue = ("%q"):format(innerValue)
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-- Fill in the condition %WRITE_INNER% and the %INNER_VALUE% to actually write
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putInner = innerWriter:gsub("%%WRITE_INNER%%", "%%1"):gsub("%%INNER_VALUE%%", formattedInnerValue)
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end
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-- Template-in the value writer (if present) and its conditional argument
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local functionCode = nextValues:gsub("PUTINNER(%b())", putInner)
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-- %VALUE% is to be filled in by the value-to-write
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valueWriter = valueWriter:gsub("%%VALUE%%", "%%1")
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-- Template-in the value writer with its argument
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functionCode = functionCode:gsub("PUTVALUE(%b())", valueWriter)
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functionCode = [[
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return function(composite, ret, encode, state)
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]] .. functionCode .. [[
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end
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]]
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return assert(loadstring(functionCode))()
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end
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local function prepareEncoder(cacheKey, nextValues, innerValue, valueWriter, innerWriter)
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local cache = outputCache[cacheKey]
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if not cache then
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cache = {}
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outputCache[cacheKey] = cache
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end
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local fun = cache[nextValues]
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if not fun then
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fun = buildFunction(nextValues, innerValue, valueWriter, innerWriter)
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cache[nextValues] = fun
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end
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return fun
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end
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local output_utility = {
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prepareEncoder = prepareEncoder
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}
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return output_utility
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