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

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/*
* 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 Mozilla strings.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 2000 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
* Scott Collins <scc@mozilla.org> (original author)
*
*/
#ifndef nsSlidingString_h___
#define nsSlidingString_h___
#include "nsAReadableString.h"
#include "nsSharedBufferList.h"
/**
* Maintains the sequence from the prev-most referenced buffer to the last buffer.
* As prev-most buffers become un-referenced, they are unlinked from the list
* and destroyed.
*
* One or more |nsSlidingSubstring|s may reference into the list. Each |nsSlidingSubstring|
* holds a reference into the prev-most buffer intersecting the
* substring it describes. The destructor of a |nsSlidingSubstring| releases this
* reference, allowing the buffer list to destroy the contiguous prefix of
* unreferenced buffers.
*
* A single instance of |nsSlidingString| may reference this list.
* Through that interface, new data can be appended onto the next-most end
* of the list. |nsSlidingString| also the client to advance its starting point.
*
*/
class NS_COM nsSlidingSharedBufferList
: public nsSharedBufferList
{
public:
nsSlidingSharedBufferList( Buffer* aBuffer ) : nsSharedBufferList(aBuffer), mRefCount(0) { }
void AcquireReference() { ++mRefCount; }
void ReleaseReference() { if ( !--mRefCount ) delete this; }
void DiscardUnreferencedPrefix( Buffer* );
private:
PRUint32 mRefCount;
};
class nsSlidingString;
/**
* a substring over a buffer list, this
*/
class NS_COM nsSlidingSubstring
: virtual public nsPromiseReadable<PRUnichar>
{
friend class nsSlidingString;
public:
typedef nsSlidingSharedBufferList::Buffer Buffer;
typedef nsSlidingSharedBufferList::Position Position;
nsSlidingSubstring()
: mStart(0,0),
mEnd(0,0),
mBufferList(0),
mLength(0)
{
// nothing else to do here
}
nsSlidingSubstring( const nsSlidingSubstring& ); // copy-constructor
nsSlidingSubstring( const nsSlidingSubstring& aString, const nsReadingIterator<PRUnichar>& aStart, const nsReadingIterator<PRUnichar>& aEnd );
nsSlidingSubstring( const nsSlidingString& );
nsSlidingSubstring( const nsSlidingString& aString, const nsReadingIterator<PRUnichar>& aStart, const nsReadingIterator<PRUnichar>& aEnd );
explicit nsSlidingSubstring( const nsAReadableString& );
// copy the supplied string into a new buffer ... there will be no modifying instance over this buffer list
void Rebind( const nsSlidingSubstring& );
void Rebind( const nsSlidingSubstring&, const nsReadingIterator<PRUnichar>&, const nsReadingIterator<PRUnichar>& );
void Rebind( const nsSlidingString& );
void Rebind( const nsSlidingString&, const nsReadingIterator<PRUnichar>&, const nsReadingIterator<PRUnichar>& );
void Rebind( const nsAReadableString& );
~nsSlidingSubstring();
virtual PRUint32 Length() const { return mLength; }
protected:
nsSlidingSubstring( nsSlidingSharedBufferList* aBufferList );
virtual const PRUnichar* GetReadableFragment( nsReadableFragment<PRUnichar>&, nsFragmentRequest, PRUint32 ) const;
private:
// can't assign into me, I'm a read-only reference
void operator=( const nsSlidingSubstring& ); // NOT TO BE IMPLEMENTED
void
init_range_from_buffer_list()
// used only from constructors
{
mStart.PointBefore(mBufferList->GetFirstBuffer());
mEnd.PointAfter(mBufferList->GetLastBuffer());
mLength = PRUint32(Position::Distance(mStart, mEnd));
}
void
acquire_ownership_of_buffer_list() const
// used only from constructors and |Rebind|, requires |mStart| already be initialized
{
mBufferList->AcquireReference();
mStart.mBuffer->AcquireNonOwningReference();
}
void
release_ownership_of_buffer_list()
{
if ( mBufferList )
{
mStart.mBuffer->ReleaseNonOwningReference();
mBufferList->DiscardUnreferencedPrefix(mStart.mBuffer);
mBufferList->ReleaseReference();
}
}
protected:
Position mStart;
Position mEnd;
nsSlidingSharedBufferList* mBufferList;
PRUint32 mLength;
};
/**
* An |nsSlidingSharedBufferList| may be modified by zero or one instances of this class.
*
*/
class NS_COM nsSlidingString
: virtual public nsPromiseReadable<PRUnichar>,
private nsSlidingSubstring
{
friend class nsSlidingSubstring;
public:
nsSlidingString( PRUnichar* aStorageStart, PRUnichar* aDataEnd, PRUnichar* aStorageEnd );
// ...created by consuming ownership of a buffer ... |aStorageStart| must point to something
// that it will be OK for the slidking string to call |nsMemory::Free| on
virtual PRUint32 Length() const { return mLength; }
// you are giving ownership to the string, it takes and keeps your buffer, deleting it (with |nsMemory::Free|) when done
void AppendBuffer( PRUnichar* aStorageStart, PRUnichar* aDataEnd, PRUnichar* aStorageEnd );
// void Append( ... ); do you want some |Append|s that copy the supplied data?
void DiscardPrefix( const nsReadingIterator<PRUnichar>& );
// any other way you want to do this?
protected:
virtual const PRUnichar* GetReadableFragment( nsReadableFragment<PRUnichar>&, nsFragmentRequest, PRUint32 ) const;
private:
void
acquire_ownership_of_buffer_list() const
// used only from constructors and |Rebind|, requires |mStart| already be initialized
{
mBufferList->AcquireReference();
mStart.mBuffer->AcquireNonOwningReference();
}
nsSlidingString( const nsSlidingString& ); // NOT TO BE IMPLEMENTED
void operator=( const nsSlidingString& ); // NOT TO BE IMPLEMENTED
};
#endif // !defined(nsSlidingString_h___)