/* 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 "../include/keima.h"
#include "Objects.h"
#include "VirtualObjectVisitor.h"

namespace ke {

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;
    }

    Ke::HandleScope **scope() {
        return &scope_;
    }

    void accept(VirtualObjectVisitor *visitor);

  private:
    Block *blocks_;
    Block first_;
    Ke::HandleScope *scope_;
};

class RootScope : public Ke::HandleScope
{
  public:
    // These are implemented in Zone.h.
    inline RootScope(Zone *zone);
};

}

#endif // _include_jc_root_scope_h_