120 lines
3.8 KiB
Lua
120 lines
3.8 KiB
Lua
--[[
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parser.lua - table based parsing
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Copyright (C) 2019 Soni L.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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--]]
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-- key for STATE
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local STATE = {}
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-- key for DATA
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local DATA = {}
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-- key for GENERATOR
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local GEN = {}
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-- key for DATA OFFSET
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local OFFDATA = {}
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local type, tostring
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= type, tostring
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local function get_next_common(state, in_pos, token)
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-- note: must preserve "token" - do not call recursively with a different token
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local transition
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if state[STATE] ~= nil then
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transition = state[STATE][token]
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if not transition then
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transition = state[STATE][""]
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end
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local recheck = true
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while recheck do
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recheck = false
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local tytrans = type(transition)
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if tytrans == "string" then
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transition = state[STATE][transition]
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recheck = true
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elseif tytrans == "function" then
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transition = transition(state, token)
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recheck = true
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end
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end
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state[STATE] = transition -- may be nil
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end
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-- must NOT use elseif here - the above may set state to nil!
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if state[STATE] == nil then
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-- unexpected token. stream consumer may attempt to recover,
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-- but we do this mostly to differentiate it from "end of stream" condition.
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return in_pos - 1, nil, "unexpected token", token, state
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end
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return in_pos, state, transition -- TODO is this what we should be returning?
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end
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local function get_next_table(state, in_pos)
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if state[DATA] == nil or #state[DATA] == 0 then return in_pos, state end
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in_pos = in_pos + 1
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local token = state[DATA][in_pos - state[OFFDATA]]
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if token == nil then
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state[OFFDATA] = in_pos - 1
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state[DATA] = state[GEN]()
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return get_next_table(state, state[OFFDATA])
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end
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return get_next_common(state, in_pos, token)
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end
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local function get_next_string(state, in_pos)
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if state[DATA] == nil or #state[DATA] == 0 then return in_pos, state end
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in_pos = in_pos + 1
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local token = state[DATA]:sub(in_pos - state[OFFDATA], in_pos - state[OFFDATA])
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if token == "" then
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state[OFFDATA] = in_pos - 1
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state[DATA] = state[GEN]()
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return get_next_string(state, state[OFFDATA])
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end
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return get_next_common(state, in_pos, token)
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end
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local function stream(defs, data)
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local state = {}
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local fn
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state[STATE] = defs
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if type(data) == "string" then
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state[DATA] = data
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state[GEN] = function() end
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fn = get_next_string
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else
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state[DATA] = data()
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state[GEN] = data
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fn = type(state[DATA]) == "string" and get_next_string or get_next_table
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end
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state[OFFDATA] = 0
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return fn, state, state[OFFDATA]
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end
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local function parse(defs, data)
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for pos, state, transemsg, etoken, estate in stream(defs, data) do
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if not state then
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-- parse error
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return nil, transemsg, etoken, estate
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elseif not transemsg then
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-- parse success (maybe) - caller needs to check state[STATE] against what it considers a successful state
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return state
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end
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end
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end
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return {
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STATE = STATE,
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stream = stream,
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parse = parse,
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}
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