cpp/third_party/antlr4-cpp-runtime-4/runtime/src/tree/ParseTree.h

/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

#pragma once

#include "support/Any.h"

namespace antlr4 {
namespace tree {

  /// An interface to access the tree of <seealso cref="RuleContext"/> objects created
  /// during a parse that makes the data structure look like a simple parse tree.
  /// This node represents both internal nodes, rule invocations,
  /// and leaf nodes, token matches.
  ///
  /// The payload is either a <seealso cref="Token"/> or a <seealso cref="RuleContext"/> object.
  // ml: This class unites 4 Java classes: RuleNode, ParseTree, SyntaxTree and Tree.
  class ANTLR4CPP_PUBLIC ParseTree {
  public:
    ParseTree();
    ParseTree(ParseTree const&) = delete;
    virtual ~ParseTree() {}

    ParseTree& operator=(ParseTree const&) = delete;

    /// The parent of this node. If the return value is null, then this
    /// node is the root of the tree.
    ParseTree *parent;

    /// If we are debugging or building a parse tree for a visitor,
    /// we need to track all of the tokens and rule invocations associated
    /// with this rule's context. This is empty for parsing w/o tree constr.
    /// operation because we don't the need to track the details about
    /// how we parse this rule.
    // ml: memory is not managed here, but by the owning class. This is just for the structure.
    std::vector<ParseTree *> children;

    /// Print out a whole tree, not just a node, in LISP format
    /// {@code (root child1 .. childN)}. Print just a node if this is a leaf.
    virtual std::string toStringTree(bool pretty = false) = 0;
    virtual std::string toString() = 0;

    /// Specialize toStringTree so that it can print out more information
    /// based upon the parser.
    virtual std::string toStringTree(Parser *parser, bool pretty = false) = 0;

    virtual bool operator == (const ParseTree &other) const;

    /// The <seealso cref="ParseTreeVisitor"/> needs a double dispatch method.
    // ml: This has been changed to use Any instead of a template parameter, to avoid the need of a virtual template function.
    virtual antlrcpp::Any accept(ParseTreeVisitor *visitor) = 0;

    /// Return the combined text of all leaf nodes. Does not get any
    /// off-channel tokens (if any) so won't return whitespace and
    /// comments if they are sent to parser on hidden channel.
    virtual std::string getText() = 0;

    /**
     * Return an {@link Interval} indicating the index in the
     * {@link TokenStream} of the first and last token associated with this
     * subtree. If this node is a leaf, then the interval represents a single
     * token and has interval i..i for token index i.
     *
     * <p>An interval of i..i-1 indicates an empty interval at position
     * i in the input stream, where 0 &lt;= i &lt;= the size of the input
     * token stream.  Currently, the code base can only have i=0..n-1 but
     * in concept one could have an empty interval after EOF. </p>
     *
     * <p>If source interval is unknown, this returns {@link Interval#INVALID}.</p>
     *
     * <p>As a weird special case, the source interval for rules matched after
     * EOF is unspecified.</p>
     */
    virtual misc::Interval getSourceInterval() = 0;
  };

  // A class to help managing ParseTree instances without the need of a shared_ptr.
  class ANTLR4CPP_PUBLIC ParseTreeTracker {
  public:
    template<typename T, typename ... Args>
    T* createInstance(Args&& ... args) {
      static_assert(std::is_base_of<ParseTree, T>::value, "Argument must be a parse tree type");
      T* result = new T(args...);
      _allocated.push_back(result);
      return result;
    }

    void reset() {
      for (auto * entry : _allocated)
        delete entry;
      _allocated.clear();
    }

  private:
    std::vector<ParseTree *> _allocated;
  };


} // namespace tree
} // namespace antlr4