Quellcode-Bibliothek

^© Kompilation durch diese Firma

[Weder Korrektheit noch Funktionsfähigkeit der Software werden zugesichert.]

Datei: symbolHandle.hpp Sprache: C

/*
* Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

#ifndef SHARE_OOPS_SYMBOLHANDLE_HPP
#define SHARE_OOPS_SYMBOLHANDLE_HPP

#include "memory/allocation.hpp"
#include "oops/symbol.hpp"

// TempNewSymbol acts as a handle class in a handle/body idiom and is
// responsible for proper resource management of the body (which is a Symbol*).
// The body is resource managed by a reference counting scheme.
// TempNewSymbol can therefore be used to properly hold a newly created or referenced
// Symbol* temporarily in scope.
//
// Routines in SymbolTable will initialize the reference count of a Symbol* before
// it becomes "managed" by TempNewSymbol instances. As a handle class, TempNewSymbol
// needs to maintain proper reference counting in context of copy semantics.
//
// In SymbolTable, new_symbol() will create a Symbol* if not already in the
// symbol table and add to the symbol's reference count.
// probe() and lookup_only() will increment the refcount if symbol is found.
template <bool TEMP>
class SymbolHandleBase : public StackObj {
  Symbol* _temp;

public:
  SymbolHandleBase() : _temp(NULL) { }

  // Conversion from a Symbol* to a SymbolHandleBase.
  // Does not increment the current reference count if temporary.
  SymbolHandleBase(Symbol *s) : _temp(s) {
    if (!TEMP) {
      assert(s != nullptr, "must not be null");
      s->increment_refcount();
    }
  }

  // Copy constructor increments reference count.
  SymbolHandleBase(const SymbolHandleBase& rhs) : _temp(rhs._temp) {
    Symbol::maybe_increment_refcount(_temp);
  }

  // Assignment operator uses a c++ trick called copy and swap idiom.
  // rhs is passed by value so within the scope of this method it is a copy.
  // At method exit it contains the former value of _temp, triggering the correct refcount
  // decrement upon destruction.
  void operator=(SymbolHandleBase rhs) {
    Symbol* tmp = rhs._temp;
    rhs._temp = _temp;
    _temp = tmp;
  }

  // Decrement reference counter so it can go away if it's unused
  ~SymbolHandleBase() {
    Symbol::maybe_decrement_refcount(_temp);
  }

  // Symbol* conversion operators
  Symbol* operator -> () const                   { return _temp; }
  bool    operator == (Symbol* o) const          { return _temp == o; }
  operator Symbol*() const                       { return _temp; }

  static unsigned int compute_hash(const SymbolHandleBase& name) {
    return (unsigned int) name->identity_hash();
  }
};

// TempNewSymbol is a temporary holder for a newly created symbol
using TempNewSymbol = SymbolHandleBase<true>;

// SymbolHandle is a non-temp symbol used to hold a symbol in a semi permanent place,
// like in a hashtable. The only difference is that the constructor increments the refcount.
using SymbolHandle = SymbolHandleBase<false>;

#endif // SHARE_OOPS_SYMBOLHANDLE_HPP

¤ Dauer der Verarbeitung: 0.14 Sekunden (vorverarbeitet) ¤

Download des Quellennavigators
Download des sprechenden Kalenders
in der Quellcodebibliothek suchen

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.