/* vim: set ts=4 sw=4 tw=99 et:

 *

 * Copyright (C) 2012 David Anderson

 *

 * This file is part of JITCraft.

 *

 * JITCraft is free software: you can redistribute it and/or modify it under

 * the terms of the GNU General Public License as published by the Free

 * Software Foundation, either version 3 of the License, or (at your option)

 * any later version.

 * 

 * Foobar is distributed in the hope that it will be useful, but WITHOUT ANY

 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License along with

 * JITCraft. If not, see http://www.gnu.org/licenses/.

 */

#ifndef _include_jc_root_scopes_h_

#define _include_jc_root_scopes_h_

#include "Objects.h"

#include "VirtualObjectVisitor.h"

namespace jc {

class RootScope;

// A RootScopeManager is essentially a specialized PoolAllocator that can

// only allocate Object ** entries. It is used to allow huge, temporary

// heap data structures like ASTs to hold safe references to objects. When

// the data structures is no longer needed, all of the roots are removed

// at once.

class RootScopeManager

{

    static const size_t kObjectsPerBlock = 4096;

    struct Block {

        Object *objects[kObjectsPerBlock];

        Object **cur;

        Object **end;

        Block *prev;

        Block(Block *prev)

          : cur(objects),

            end(objects + kObjectsPerBlock),

            prev(prev)

        {

        }

    };

  private:

    bool grow();

    void unwindSlow(Object **position);

  public:

    RootScopeManager();

    ~RootScopeManager();

    Object **position() const {

        return blocks_->cur;

    }

    void unwind(Object **position) {

        if (position >= blocks_->cur && position <= blocks_->end) {

            blocks_->cur = position;

            return;

        }

        unwindSlow(position);

    }

    Object **make(Object *obj) {

        assert(scope_);

        if (blocks_->cur + 1 > blocks_->end) {

            if (!grow())

                return NULL;

        }

        Object **ptr = blocks_->cur;

        blocks_->cur++;

        *ptr = obj;

        return ptr;

    }

    RootScope **scope() {

        return &scope_;

    }

    void accept(VirtualObjectVisitor *visitor);

  private:

    Block *blocks_;

    Block first_;

    RootScope *scope_;

};

class RootScope

{

    Zone *zone_;

    Object **position_;

    RootScope *prev_;

  public:

    // These are implemented in Zone.h.

    inline RootScope(Zone *zone);

    inline ~RootScope();

};

}

#endif // _include_jc_root_scope_h_