//===- GCFactoryListTraits.h ----------------------------------------------===//
//
//                     The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef MCLD_SUPPORT_GCFACTORYLISTTRAITS_H_
#define MCLD_SUPPORT_GCFACTORYLISTTRAITS_H_

#include <llvm/ADT/ilist.h>
#include <llvm/ADT/ilist_node.h>

#include <assert.h>

namespace mcld {

/** \class GCFactoryListTraits
 *  \brief GCFactoryListTraits provides trait class for llvm::iplist when
 *  the nodes in the list is produced by GCFactory.
 */
template <typename DataType>
class GCFactoryListTraits : public llvm::ilist_default_traits<DataType> {
 private:
  class SentinelNode : public DataType {
   public:
    SentinelNode() {}
  };

 public:
  // override the traits provided in llvm::ilist_sentinel_traits since we've
  // defined our own sentinel.
  DataType* createSentinel() const {
    return reinterpret_cast<DataType*>(&mSentinel);
  }

  static void destroySentinel(DataType* pData) {}

  DataType* provideInitialHead() const { return createSentinel(); }

  DataType* ensureHead(DataType* pData) const { return createSentinel(); }

  static void noteHead(DataType* pNew, DataType* pSentinel) {}

  // override the traits provided in llvm::ilist_node_traits since
  static DataType* createNode(const DataType& V) {
    assert(false && "Only GCFactory knows how to create a node.");
  }
  static void deleteNode(DataType* V) {
    // No action. GCFactory will handle it by itself.
  }

 private:
  mutable SentinelNode mSentinel;
};

}  // namespace mcld

#endif  // MCLD_SUPPORT_GCFACTORYLISTTRAITS_H_