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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SKSL_NFA
#define SKSL_NFA
#include "NFAState.h"
#include "RegexNode.h"
/**
* A nondeterministic finite automaton for matching regular expressions. The NFA is initialized with
* a number of regular expressions, and then matches a string against all of them simultaneously.
*/
struct NFA {
/**
* Adds a new regular expression to the set of expressions matched by this automaton, returning
* its index.
*/
int addRegex(const RegexNode& regex) {
std::vector<int> accept;
// we reserve token 0 for END_OF_FILE, so this starts at 1
accept.push_back(this->addState(NFAState(++fRegexCount)));
std::vector<int> startStates = regex.createStates(this, accept);
fStartStates.insert(fStartStates.end(), startStates.begin(), startStates.end());
return fStartStates.size() - 1;
}
/**
* Adds a new state to the NFA, returning its index.
*/
int addState(NFAState s) {
fStates.push_back(std::move(s));
return fStates.size() - 1;
}
/**
* Matches a string against all of the regexes added to this NFA. Returns the index of the first
* (in addRegex order) matching expression, or -1 if no match. This is relatively slow and used
* only for debugging purposes; the NFA should be converted to a DFA before actual use.
*/
int match(std::string s) const;
int fRegexCount = 0;
std::vector<NFAState> fStates;
std::vector<int> fStartStates;
};
#endif
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