gecko-dev/xpcom/string/public/nsSharedString.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
 * The contents of this file are subject to the Netscape 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/NPL/
 *
 * 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 mozilla.org code.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Original Author:
 *   Scott Collins <scc@mozilla.org>
 *
 * Contributor(s):
 */

#ifndef nsSharedString_h___
#define nsSharedString_h___

#ifndef nsAReadableString_h___
#include "nsAReadableString.h"
#endif

template <class CharT>
class basic_nsSharedString
      : public basic_nsAReadableString<CharT>
    /*
      ...
    */
  {
    public:
      basic_nsSharedString( const CharT* data, size_t length )
          : mRefCount(0), mData(data), mLength(length)
        {
          // nothing else to do here
        }

    private:
      ~basic_nsSharedString() { } // You can't sub-class me, or make an instance of me on the stack

        // NOT TO BE IMPLEMENTED
        // we're reference counted, remember.  copying and passing by value are wrong
      // basic_nsSharedString(); // we define at least one constructor, so the default constructor will not be auto-generated.  It's wrong to create me with no data anyway
      basic_nsSharedString( const basic_nsSharedString<CharT>& ); // copy-constructor, the auto generated one would reference somebody elses data
      void operator=( const basic_nsSharedString<CharT>& );       // copy-assignment operator
      
      // operator delete?

    public:

      virtual const CharT* GetReadableFragment( nsReadableFragment<CharT>&, nsFragmentRequest, PRUint32 ) const;

      virtual
      PRUint32
      Length() const
        {
          return mLength;
        }

      nsrefcnt
      AddRef() const
        {
          return ++mRefCount;
        }

      nsrefcnt
      Release() const
        {
          nsrefcnt result = --mRefCount;
          if ( !mRefCount )
            {
              // would have to call my destructor by hand here, if there was anything to destruct
              operator delete(this); // form of |delete| should always match the |new|
            }
          return result;
        }

    private:
      mutable nsrefcnt  mRefCount;
      const CharT*      mData;
      size_t            mLength;
  };

NS_DEF_TEMPLATE_STRING_COMPARISON_OPERATORS(basic_nsSharedString<CharT>, CharT)

template <class CharT>
const CharT*
basic_nsSharedString<CharT>::GetReadableFragment( nsReadableFragment<CharT>& aFragment, nsFragmentRequest aRequest, PRUint32 anOffset ) const
  {
    switch ( aRequest )
      {
        case kFirstFragment:
        case kLastFragment:
        case kFragmentAt:
          aFragment.mEnd = (aFragment.mStart = mData) + mLength;
          return aFragment.mStart + anOffset;
        
        case kPrevFragment:
        case kNextFragment:
        default:
          return 0;
      }
  }



template <class CharT>
class basic_nsSharedStringPtr
  {
    public:
        // default constructor
      basic_nsSharedStringPtr() : mRawPtr(0) { }

        // copy-constructor
      basic_nsSharedStringPtr( const basic_nsSharedStringPtr<CharT>& rhs )
          : mRawPtr(rhs.mRawPtr)
        {
          mRawPtr->AddRef();
        }

     ~basic_nsSharedStringPtr()
        {
          if ( mRawPtr )
            mRawPtr->Release();
        }

        // copy-assignment operator
      basic_nsSharedStringPtr<CharT>&
      operator=( const basic_nsSharedStringPtr<CharT>& );

      basic_nsSharedString<CharT>*
      operator->() const
        {
          NS_PRECONDITION(mRawPtr != 0, "You can't dereference a NULL string pointer with operator->().");
          return mRawPtr;
        }

      basic_nsSharedString<CharT>&
      operator*() const
        {
          NS_PRECONDITION(mRawPtr != 0, "You can't dereference a NULL string pointer with operator->().");
          return *mRawPtr;
        }

    private:
      const basic_nsSharedString<CharT>*  mRawPtr;
  };

template <class CharT>
basic_nsSharedStringPtr<CharT>&
basic_nsSharedStringPtr<CharT>::operator=( const basic_nsSharedStringPtr<CharT>& rhs )
    // Not |inline|
  {
    if ( rhs.mRawPtr )
      rhs.mRawPtr->AddRef();
    basic_nsSharedString<CharT>* oldPtr = mRawPtr;
    mRawPtr = rhs.mRawPtr;
    if ( oldPtr )
      oldPtr->Release();
  }


template <class CharT>
basic_nsSharedString<CharT>*
new_nsSharedString( const basic_nsAReadableString<CharT>& aReadable )
  {
    size_t object_size    = ((sizeof(basic_nsSharedString<CharT>) + sizeof(CharT) - 1) / sizeof(CharT)) * sizeof(CharT);
    size_t string_length  = aReadable.Length();
    size_t string_size    = string_length * sizeof(CharT);

    void* object_ptr = operator new(object_size + string_size);
    if ( object_ptr )
      {
        typedef CharT* CharT_ptr;
        CharT* string_ptr = CharT_ptr(NS_STATIC_CAST(unsigned char*, object_ptr) + object_size);

        nsReadingIterator<CharT> fromBegin, fromEnd;
        CharT* toBegin = string_ptr;
        copy_string(aReadable.BeginReading(fromBegin), aReadable.EndReading(fromEnd), toBegin);
        return new (object_ptr) basic_nsSharedString<CharT>(string_ptr, string_length);
      }

    return 0;
  }


typedef basic_nsSharedString<PRUnichar>     nsSharedString;
typedef basic_nsSharedString<char>          nsSharedCString;

typedef basic_nsSharedStringPtr<PRUnichar>  nsSharedStringPtr;
typedef basic_nsSharedStringPtr<char>       nsSharedCStringPtr;


#endif // !defined(nsSharedString_h___)