1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/jitcraft/RootScopes.h	Tue Jul 03 00:21:37 2012 -0700
     1.3 @@ -0,0 +1,107 @@
     1.4 +/* vim: set ts=4 sw=4 tw=99 et:
     1.5 + *
     1.6 + * Copyright (C) 2012 David Anderson
     1.7 + *
     1.8 + * This file is part of JITCraft.
     1.9 + *
    1.10 + * JITCraft is free software: you can redistribute it and/or modify it under
    1.11 + * the terms of the GNU General Public License as published by the Free
    1.12 + * Software Foundation, either version 3 of the License, or (at your option)
    1.13 + * any later version.
    1.14 + * 
    1.15 + * Foobar is distributed in the hope that it will be useful, but WITHOUT ANY
    1.16 + * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    1.17 + * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
    1.18 + *
    1.19 + * You should have received a copy of the GNU General Public License along with
    1.20 + * JITCraft. If not, see http://www.gnu.org/licenses/.
    1.21 + */
    1.22 +#ifndef _include_jc_root_scopes_h_
    1.23 +#define _include_jc_root_scopes_h_
    1.24 +
    1.25 +#include "Objects.h"
    1.26 +
    1.27 +namespace jc {
    1.28 +
    1.29 +class RootScope;
    1.30 +
    1.31 +// A RootScopeManager is essentially a specialized PoolAllocator that can
    1.32 +// only allocate Object ** entries. It is used to allow huge, temporary
    1.33 +// heap data structures like ASTs to hold safe references to objects. When
    1.34 +// the data structures is no longer needed, all of the roots are removed
    1.35 +// at once.
    1.36 +class RootScopeManager
    1.37 +{
    1.38 +    static const size_t kObjectsPerBlock = 4096;
    1.39 +
    1.40 +    struct Block {
    1.41 +        Object *objects[kObjectsPerBlock];
    1.42 +        Object **cur;
    1.43 +        Object **end;
    1.44 +        Block *prev;
    1.45 +
    1.46 +        Block(Block *prev)
    1.47 +          : cur(objects),
    1.48 +            end(objects + kObjectsPerBlock),
    1.49 +            prev(prev)
    1.50 +        {
    1.51 +        }
    1.52 +    };
    1.53 +
    1.54 +  private:
    1.55 +    bool grow();
    1.56 +    void unwindSlow(Object **position);
    1.57 +
    1.58 +  public:
    1.59 +    RootScopeManager();
    1.60 +    ~RootScopeManager();
    1.61 +
    1.62 +    Object **position() const {
    1.63 +        return blocks_->cur;
    1.64 +    }
    1.65 +
    1.66 +    void unwind(Object **position) {
    1.67 +        if (position >= blocks_->cur && position <= blocks_->end) {
    1.68 +            blocks_->cur = position;
    1.69 +            return;
    1.70 +        }
    1.71 +        unwindSlow(position);
    1.72 +    }
    1.73 +
    1.74 +    Object **make(Object *obj) {
    1.75 +        assert(scope_);
    1.76 +        if (blocks_->cur + 1 > blocks_->end) {
    1.77 +            if (!grow())
    1.78 +                return NULL;
    1.79 +        }
    1.80 +        Object **ptr = blocks_->cur;
    1.81 +        blocks_->cur++;
    1.82 +        *ptr = obj;
    1.83 +        return ptr;
    1.84 +    }
    1.85 +
    1.86 +    RootScope **scope() {
    1.87 +        return &scope_;
    1.88 +    }
    1.89 +
    1.90 +  private:
    1.91 +    Block *blocks_;
    1.92 +    Block first_;
    1.93 +    RootScope *scope_;
    1.94 +};
    1.95 +
    1.96 +class RootScope
    1.97 +{
    1.98 +    Zone *zone_;
    1.99 +    Object **position_;
   1.100 +    RootScope *prev_;
   1.101 +
   1.102 +  public:
   1.103 +    // These are implemented in Zone.h.
   1.104 +    inline RootScope(Zone *zone);
   1.105 +    inline ~RootScope();
   1.106 +};
   1.107 +
   1.108 +}
   1.109 +
   1.110 +#endif // _include_jc_root_scope_h_