67 lines
1.6 KiB
Lua
67 lines
1.6 KiB
Lua
local function _parse(str, init)
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local pos = init
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if string.find(str, "^%(", pos) then
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pos = pos + 1
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local list = {};
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while true do
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if string.find(str, "^%)", pos) then
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pos = pos + 1
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return list, pos
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end
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local child, new_pos = _parse(str, pos)
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if not child then
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error(string.format("expected ')', '(', or atom at index %d", pos))
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end
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table.insert(list, child)
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pos = new_pos
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end
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else
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local pos = init
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local len_str = string.match(str, "^%d+", pos)
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if not len_str then
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error(string.format("expected '(' or atom at index %d", pos))
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end
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local len = tonumber(len_str)
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pos = pos+#len_str
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if not string.find(str, "^:", pos) then error(string.format("expected ':' at index %d", pos)) end
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pos = pos + 1
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local value = string.sub(str, pos, pos + len - 1)
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if #value < len then error(string.format("unexpected end of string at index %d", pos)) end
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pos = pos + len
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return value, pos
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end
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end
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local function parse(str)
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local value, pos = _parse(str, 1)
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if pos <= #str then
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error(string.format("extra characters at index %d", pos))
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end
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return value
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end
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local function _serialize(tokens, obj)
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if type(obj) == "table" then
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table.insert(tokens, "(")
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for _, item in ipairs(obj) do
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_serialize(tokens, item)
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end
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table.insert(tokens, ")")
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else
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local s = tostring(obj)
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table.insert(tokens, tostring(#s))
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table.insert(tokens, ":")
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table.insert(tokens, s)
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end
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end
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local function serialize(obj)
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local tokens = {}
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_serialize(tokens, obj)
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return table.concat(tokens)
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end
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return {parse = parse, serialize = serialize}
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