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91 lines
2.4 KiB
91 lines
2.4 KiB
'use strict';
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var INITIAL_STATE = 1;
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var FAIL_STATE = 0;
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/**
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* A StateMachine represents a deterministic finite automaton.
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* It can perform matches over a sequence of values, similar to a regular expression.
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*/
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class StateMachine {
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constructor(dfa) {
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this.stateTable = dfa.stateTable;
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this.accepting = dfa.accepting;
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this.tags = dfa.tags;
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}
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/**
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* Returns an iterable object that yields pattern matches over the input sequence.
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* Matches are of the form [startIndex, endIndex, tags].
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*/
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match(str) {
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var self = this;
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return {
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*[Symbol.iterator]() {
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var state = INITIAL_STATE;
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var startRun = null;
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var lastAccepting = null;
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var lastState = null;
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for (var p = 0; p < str.length; p++) {
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var c = str[p];
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lastState = state;
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state = self.stateTable[state][c];
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if (state === FAIL_STATE) {
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// yield the last match if any
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if (startRun != null && lastAccepting != null && lastAccepting >= startRun) {
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yield [startRun, lastAccepting, self.tags[lastState]];
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} // reset the state as if we started over from the initial state
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state = self.stateTable[INITIAL_STATE][c];
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startRun = null;
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} // start a run if not in the failure state
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if (state !== FAIL_STATE && startRun == null) {
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startRun = p;
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} // if accepting, mark the potential match end
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if (self.accepting[state]) {
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lastAccepting = p;
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} // reset the state to the initial state if we get into the failure state
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if (state === FAIL_STATE) {
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state = INITIAL_STATE;
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}
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} // yield the last match if any
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if (startRun != null && lastAccepting != null && lastAccepting >= startRun) {
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yield [startRun, lastAccepting, self.tags[state]];
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}
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}
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};
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}
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/**
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* For each match over the input sequence, action functions matching
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* the tag definitions in the input pattern are called with the startIndex,
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* endIndex, and sub-match sequence.
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*/
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apply(str, actions) {
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for (var [start, end, tags] of this.match(str)) {
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for (var tag of tags) {
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if (typeof actions[tag] === 'function') {
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actions[tag](start, end, str.slice(start, end + 1));
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}
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}
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}
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}
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}
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module.exports = StateMachine;
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//# sourceMappingURL=index.js.map
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