/* 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"

 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_;

     }

   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_