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Diffstat (limited to 'src/cratera/parser.lua')
| -rw-r--r-- | src/cratera/parser.lua | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/src/cratera/parser.lua b/src/cratera/parser.lua new file mode 100644 index 0000000..ade568c --- /dev/null +++ b/src/cratera/parser.lua @@ -0,0 +1,202 @@ +--[[ + This file is part of Cratera Compiler + Copyright (C) 2019 Soni L. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU Affero General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Affero General Public License for more details. + + You should have received a copy of the GNU Affero General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. +--]] + +local function ts(self) return getmetatable(self).__name end + +-- key for STATE +local STATE = setmetatable({}, {__name="STATE", __tostring=ts}) +-- key for DATA +local DATA = setmetatable({}, {__name="DATA", __tostring=ts}) +-- key for GENERATOR +local GEN = setmetatable({}, {__name="GEN", __tostring=ts}) +-- key for DATA OFFSET +local OFFDATA = setmetatable({}, {__name="OFFDATA", __tostring=ts}) +-- key for End of Stream +local EOZ = setmetatable({}, {__name="EOZ", __tostring=ts}) +-- key for number rules (prevent conflict with hooks) +local NUMBER = setmetatable({}, {__name="NUMBER", __tostring=ts}) +-- key for fallback rules (prevent conflict with empty string) +local FALLBACK = setmetatable({}, {__name="FALLBACK", __tostring=ts}) + +local optimize_lookups = {} +for i=0, 255 do + optimize_lookups[i] = string.char(i) +end + +local type, tostring, string_byte + = type, tostring, string.byte + +local function get_next_common(state, in_pos, token) + -- note: must preserve "token" - do not call recursively with a different token + local transition, retry + local st = state[STATE] + if st then + local rule = st[token] + if not rule and token == EOZ then + return in_pos, state + end + if type(token) == "number" then + rule = st[NUMBER] + end + do -- pre-hooks + local pos = -1 + local hook = st[pos] + while hook ~= nil do + if hook then + hook(state, token, rule) + end + pos = pos - 1 + hook = st[pos] + end + end + transition = rule + if transition == nil then + transition = st[FALLBACK] + end + local recheck = true + while recheck do + recheck = false + local tytrans = type(transition) + if tytrans == "string" then + transition = st[transition] + recheck = true + elseif tytrans == "function" then + transition, retry = transition(state, token) + recheck = true + elseif tytrans == "table" and st[transition] ~= nil then + transition = st[transition] + recheck = true + end + end + do -- post-hooks CANNOT USE ipairs HERE BECAUSE Lua 5.1/5.2 + local pos = 1 + local hook = st[pos] + while hook ~= nil do + if hook then + hook(state, token, rule) + end + pos = pos + 1 + hook = st[pos] + end + end + state[STATE] = transition -- may be nil or false + end + -- must NOT use elseif here - the above may set state to nil or false! + if not state[STATE] then + -- unexpected token. stream consumer may attempt to recover, + -- but we do this mostly to differentiate it from "end of stream" condition. + return in_pos - 1, nil, "unexpected token", token, state, st + end + if retry then in_pos = in_pos - 1 end + return in_pos, state, transition -- TODO is this what we should be returning? +end + +local function get_next_table(state, in_pos) + if state[DATA] == nil or #state[DATA] == 0 then + if state[STATE] == nil then + return in_pos, state + else + return get_next_common(state, in_pos, EOZ) + end + end + in_pos = in_pos + 1 + local token = state[DATA][in_pos - state[OFFDATA]] + if token == nil then + state[OFFDATA] = in_pos - 1 + state[DATA] = state[GEN]() + return get_next_table(state, state[OFFDATA]) + end + return get_next_common(state, in_pos, token) +end + +local function get_next_string(state, in_pos) + if state[DATA] == nil or #state[DATA] == 0 then + if state[STATE] == nil then + return in_pos, state + else + return get_next_common(state, in_pos, EOZ) + end + end + in_pos = in_pos + 1 + local token = optimize_lookups[string_byte(state[DATA], in_pos - state[OFFDATA], in_pos - state[OFFDATA])] + if token == nil then + state[OFFDATA] = in_pos - 1 + state[DATA] = state[GEN]() + return get_next_string(state, state[OFFDATA]) + end + return get_next_common(state, in_pos, token) +end + +local function stream(defs, data, state) + local state = state or {} + local fn + state[STATE] = defs + if type(data) == "function" then + state[DATA] = data() + state[GEN] = data + else + state[DATA] = data + state[GEN] = function() end + end + fn = type(state[DATA]) == "table" and get_next_table or get_next_string + state[OFFDATA] = 0 + return fn, state, state[OFFDATA] +end + +local function parse(defs, data, state) + for pos, state, transemsg, etoken, estate in stream(defs, data, state) do + if not state then + -- parse error + return nil, transemsg, etoken, estate + elseif not transemsg then + -- parse success (maybe) - caller needs to check state[STATE] against what it considers a successful state + return state + end + end +end + +-- not used by any of the above but useful for others + +local COLLECT = {} + +return { + STATE = STATE, + DATA = DATA, + COLLECT = COLLECT, + EOZ = EOZ, + FALLBACK = FALLBACK, + NUMBER = NUMBER, + stream = stream, + parse = parse, + -- common utility function + selfify = function(t, id) + t[id or "self"] = t + return t + end, + -- common hook + collect_fallback = function(state, token, rule) + if not rule then + local t = state[COLLECT] + t[#t+1] = token + if t.coalesce and #t >= t.coalesce then + t[1] = table.concat(t) + for i=2, #t do t[i] = nil end + end + end + end, +} |