RegexParser.h

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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_REGEXPARSER
#define SKSL_REGEXPARSER
 
#include "src/sksl/lex/RegexNode.h"
 
#include <stack>
#include <string>
 
/**
 * Turns a simple regular expression into a parse tree. The regular expression syntax supports only
 * the basic quantifiers ('*', '+', and '?'), alternation ('|'), character sets ('[a-z]'), and
 * groups ('()').
 */
class RegexParser {
public:
    RegexNode parse(std::string source);
 
private:
    inline static constexpr char END = '\0';
 
    char peek();
 
    void expect(char c);
 
    RegexNode pop();
 
    /**
     * Matches a char literal, parenthesized group, character set, or dot ('.').
     */
    void term();
 
    /**
     * Matches a term followed by an optional quantifier ('*', '+', or '?').
     */
    void quantifiedTerm();
 
    /**
     * Matches a sequence of quantifiedTerms.
     */
    void sequence();
 
    /**
     * Returns a node representing the given escape character (e.g. escapeSequence('n') returns a
     * node which matches a newline character).
     */
    RegexNode escapeSequence(char c);
 
    /**
     * Matches a literal character or escape sequence.
     */
    void literal();
 
    /**
     * Matches a dot ('.').
     */
    void dot();
 
    /**
     * Matches a parenthesized group.
     */
    void group();
 
    /**
     * Matches a literal character, escape sequence, or character range from a character set.
     */
    void setItem();
 
    /**
     * Matches a character set.
     */
    void set();
 
    void regex();
 
    std::string fSource;
 
    size_t fIndex;
 
    std::stack<RegexNode> fStack;
};
 
#endif