gecko-dev/xpcom/ds/nsBaseHashtable.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is C++ hashtable templates.
 *
 * The Initial Developer of the Original Code is
 * Benjamin Smedberg.
 * Portions created by the Initial Developer are Copyright (C) 2002
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#ifndef nsBaseHashtable_h__
#define nsBaseHashtable_h__

#include "nsTHashtable.h"
#include NEW_H
typedef struct PRRWLock PRRWLock;

template<class KeyClass,class DataType,class UserDataType>
class nsBaseHashtable; // forward declaration

/**
 * the private nsTHashtable::EntryType class used by nsBaseHashtable
 * @see nsTHashtable for the specification of this class
 * @see nsBaseHashtable for template parameters
 */
template<class KeyClass,class DataType>
class nsBaseHashtableET : public KeyClass
{
public:
  DataType mData;
  friend class nsTHashtable< nsBaseHashtableET<KeyClass,DataType> >;

private:
  typedef typename KeyClass::KeyType KeyType;
  typedef typename KeyClass::KeyTypePointer KeyTypePointer;
  
  nsBaseHashtableET(KeyTypePointer aKey);
  nsBaseHashtableET(const nsBaseHashtableET<KeyClass,DataType>& toCopy);
  ~nsBaseHashtableET();
};

/**
 * templated hashtable for simple data types
 * This class manages simple data types that do not need construction or
 * destruction. Thread-safety is optional, via a flag in Init()
 *
 * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
 *   for a complete specification.
 * @param DataType the datatype stored in the hashtable,
 *   for example, PRUint32 or nsCOMPtr.  If UserDataType is not the same,
 *   DataType must implicitly cast to UserDataType
 * @param UserDataType the user sees, for example PRUint32 or nsISupports*
 */
template<class KeyClass,class DataType,class UserDataType>
class nsBaseHashtable :
  protected nsTHashtable< nsBaseHashtableET<KeyClass,DataType> >
{
public:
  typedef typename KeyClass::KeyType KeyType;
  typedef nsBaseHashtableET<KeyClass,DataType> EntryType;

  /**
   * The constructor does not initialize, you must call Init() after
   * construction.
   */
  nsBaseHashtable();

  /**
   * destructor finalizes and deallocates hashtable
   */
  ~nsBaseHashtable();

  /**
   * Initialize the object.
   * @param initSize the initial number of buckets in the hashtable,
       default 16
   * @param threadSafe whether to provide read/write
   * locking on all class methods
   * @return    PR_TRUE if the object was initialized properly.
   */
  PRBool Init(PRUint32 initSize   = PL_DHASH_MIN_SIZE,
              PRBool   threadSafe = PR_FALSE);

  /**
   * retrieve the value for a key.
   * @param aKey the key to retreive
   * @param pData data associated with this key will be placed at this
   *   pointer.  If you only need to check if the key exists, pData
   *   may be null.
   * @return PR_TRUE if the key exists. If key does not exist, pData is not
   *   modified.
   */
  PRBool Get(KeyType aKey, UserDataType* pData) const;

  /**
   * put a new value for the associated key
   * @param aKey the key to put
   * @param aData the new data
   * @return always PR_TRUE, unless memory allocation failed
   */
  PRBool Put(KeyType aKey, UserDataType aData);

  /**
   * remove the data for the associated key
   * @param aKey the key to remove from the hashtable
   */
  void Remove(KeyType aKey);

  /**
   * function type provided by the application for enumeration.
   * currently, only "read" enumeration is supported.  If you need to change
   * or remove entries during enumeration, it might could be arranged.
   * @param aKey the key being enumerated
   * @param aData data being enumerated
   * @parm userArg passed unchanged from Enumerate
   * @return either
   *   @link PLDHashOperator::PL_DHASH_NEXT PL_DHASH_NEXT @endlink or
   *   @link PLDHashOperator::PL_DHASH_STOP PL_DHASH_STOP @endlink
   */
  typedef PLDHashOperator
    (*PR_CALLBACK EnumReadFunction)(KeyType  aKey,
                                    DataType aData,
                                    void*    userArg);

  /**
   * enumerate entries in the hashtable, without allowing changes
   * this function read-locks the hashtable, so other threads may read keys
   * at the same time in multi-thread environments.
   * @param enumFunc enumeration callback
   * @param userArg passed unchanged to the EnumReadFunction
   */
  void EnumerateRead(EnumReadFunction enumFunc, void* userArg) const;

  /**
   * reset the hashtable, removing all entries
   */
  void Clear();

protected:
  PRRWLock* mLock;

  /**
   * used internally during EnumerateRead.  Allocated on the stack.
   * @param func the enumerator passed to EnumerateRead
   * @param userArg the userArg passed to EnumerateRead
   */
  struct s_EnumReadArgs
  {
    EnumReadFunction func;
    void* userArg;
  };

  static PLDHashOperator s_EnumReadStub(PLDHashTable    *table,
                                        PLDHashEntryHdr *hdr,
                                        PRUint32         number,
                                        void            *arg);
};

#ifndef HAVE_CPP_EXTERN_INSTANTIATION
  #include "nsBaseHashtableImpl.h"
#endif

#endif // nsBaseHashtable_h__