source: src/AST/Node.hpp @ dafe9e1

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Node.hpp --
//
// Author           : Thierry Delisle
// Created On       : Wed May 8 10:27:04 2019
// Last Modified By : Andrew Beach
// Last Modified On : Mon Jun  3 13:26:00 2019
// Update Count     : 5
//

#pragma once

#include <cassert>
#include <iosfwd>

namespace ast {

class Visitor;

/// Base class for all AST nodes.
/// Keeps both strong and weak reference counts.
class Node {
public:
        // override defaults to ensure assignment doesn't
        // change/share reference counts
        Node() = default;
        Node(const Node&) : strong_count(0), weak_count(0) {}
        Node(Node&&) : strong_count(0), weak_count(0) {}
        Node& operator= (const Node&) = delete;
        Node& operator= (Node&&) = delete;
        virtual ~Node() = default;

        virtual const Node * accept( Visitor & v ) const = 0;

        /// Types of node references
        enum class ref_type {
                strong,
                weak
        };

private:
        /// Make a copy of this node; should be overridden in subclass with more precise return type
        virtual Node * clone() const = 0;

        /// Must be copied in ALL derived classes
        template<typename node_t>
        friend node_t * mutate(const node_t * node);

        mutable size_t strong_count = 0;
        mutable size_t weak_count = 0;

        void increment(ref_type ref) const {
                switch (ref) {
                        case ref_type::strong: strong_count++; break;
                        case ref_type::weak  : weak_count  ++; break;
                }
        }

        void decrement(ast::Node::ref_type ref) const {
                switch (ref) {
                        case ref_type::strong: strong_count--; break;
                        case ref_type::weak  : weak_count  --; break;
                }

                if(!strong_count && !weak_count) {
                        delete this;
                }
        }

        template< typename node_t, enum Node::ref_type ref_t >
        friend class ptr_base;
};

// Mutate a node, non-member function to avoid static type
// problems and be able to use auto return
template<typename node_t>
node_t * mutate( const node_t * node ) {
        if (node->strong_count <= 1) {
                return const_cast<node_t *>(node);
        }

        assertf(
                node->weak_count == 0,
                "Error: mutating node with weak references to it will invalided some references"
        );
        return node->clone();
}

std::ostream& operator<< ( std::ostream& out, const Node * node );

/// Call a visitor on a possibly-null node
template<typename node_t>
auto maybe_accept( const node_t * n, Visitor & v ) -> decltype( n->accept(v) ) {
        return n ? n->accept( v ) : nullptr;
}

/// Base class for the smart pointer types
/// should never really be used.
template< typename node_t, enum Node::ref_type ref_t >
class ptr_base {
public:
        ptr_base() : node(nullptr) {}
        ptr_base( const node_t * n ) : node(n) { if( node ) _inc(node); }
        ~ptr_base() { if( node ) { auto tmp = node; node = nullptr; _dec(tmp); } }

        ptr_base( const ptr_base & o ) : node(o.node) {
                if( node ) _inc(node);
        }

        ptr_base( ptr_base && o ) : node(o.node) { o.node = nullptr; }

        template< enum Node::ref_type o_ref_t >
        ptr_base( const ptr_base<node_t, o_ref_t> & o ) : node(o.node) {
                if( node ) _inc(node);
        }

        template< enum Node::ref_type o_ref_t >
        ptr_base( ptr_base<node_t, o_ref_t> && o ) : node(o.node) {
                if( node ) _inc(node);
        }

        template<typename o_node_t>
        ptr_base & operator=( const o_node_t * node ) {
                assign( strict_dynamic_cast<const node_t *, nullptr>(node) );
                return *this;
        }

        ptr_base & operator=( const ptr_base & o ) {
                assign(o.node);
                return *this;
        }

        ptr_base & operator=( ptr_base && o ) {
                if ( node == o.node ) return *this;
                if ( node ) _dec(node);
                node = o.node;
                o.node = nullptr;
                return *this;
        }

        template< enum Node::ref_type o_ref_t >
        ptr_base & operator=( const ptr_base<node_t, o_ref_t> & o ) {
                assign(o.node);
                return *this;
        }

        template< enum Node::ref_type o_ref_t >
        ptr_base & operator=( ptr_base<node_t, o_ref_t> && o ) {
                assign(o.node);
                return *this;
        }

        const node_t * get() const { return  node; }
        const node_t * operator->() const { return  node; }
        const node_t & operator* () const { return *node; }
        explicit operator bool() const { return node; }
        operator const node_t * () const { return node; }

        /// wrapper for convenient access to dynamic_cast
        template<typename o_node_t>
        const o_node_t * as() const { return dynamic_cast<const o_node_t *>(node); }

        /// Returns a mutable version of the pointer in this node.
        node_t * get_and_mutate();

        /// Sets this pointer to a mutated version of a pointer (possibly) owned elsehere.
        /// Returns a mutable version of the pointer in this node.
        node_t * set_and_mutate( const node_t * n );

        using ptr = const node_t *;

private:
        void assign( const node_t * other ) {
                if( other ) _inc(other);
                if( node  ) _dec(node );
                node = other;
        }

        void _inc( const node_t * other );
        void _dec( const node_t * other );

protected:
        const node_t * node;
};

/// Owning pointer to node
template< typename node_t >
using ptr = ptr_base< node_t, Node::ref_type::strong >;

/// Observing pointer to node
template< typename node_t >
using readonly = ptr_base< node_t, Node::ref_type::weak >;
}

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //