    /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
    /*
     * This file is part of the LibreOffice project.
     *
     * This Source Code Form is subject to the terms of the Mozilla Public
     * License, v. 2.0. If a copy of the MPL was not distributed with this
     * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     *
     * This file incorporates work covered by the following license notice:
     *
     *   Licensed to the Apache Software Foundation (ASF) under one or more
     *   contributor license agreements. See the NOTICE file distributed
     *   with this work for additional information regarding copyright
     *   ownership. The ASF licenses this file to you under the Apache
     *   License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 .
     */

    #include <rtl/alloc.h>

    #include <limits>
    #include <string.h>

    #include <com/sun/star/uno/Sequence.hxx>

    #include <com/sun/star/uno/Exception.hpp>

    using namespace ::com::sun::star::uno;

    #include "streamhelper.hxx"

    namespace io_stm {

    void MemFIFO::write( const Sequence< sal_Int8 > &seq )
    {
        writeAt(getSize(), seq);
    }

    void MemFIFO::read( Sequence<sal_Int8> &seq , sal_Int32 nBufferLen )
    {
        readAt(0, seq , nBufferLen);
        forgetFromStart( nBufferLen );
    }

    void MemFIFO::skip( sal_Int32 nBytesToSkip )
    {
        forgetFromStart( nBytesToSkip );
    }

    MemRingBuffer::MemRingBuffer()
    {
        m_nBufferLen            = 0;
        m_p                     = nullptr;
        m_nStart                = 0;
        m_nOccupiedBuffer       = 0;
    }

    MemRingBuffer::~MemRingBuffer()
    {
        std::free( m_p );
    }

    void MemRingBuffer::resizeBuffer( sal_Int32 nMinSize )
    {
        sal_Int32 nNewLen = 1;

        while( nMinSize > nNewLen ) {
            nNewLen = nNewLen << 1;
        }

        // buffer never shrinks !
        if( nNewLen < m_nBufferLen ) {
            nNewLen = m_nBufferLen;
        }

        if( nNewLen != m_nBufferLen ) {
            m_p = static_cast<sal_Int8 *>(std::realloc( m_p , nNewLen ));
            if( !m_p ) {
                throw css::io::BufferSizeExceededException(
                    "MemRingBuffer::resizeBuffer BufferSizeExceededException");
            }

            if( m_nStart + m_nOccupiedBuffer > m_nBufferLen ) {
                memmove( &( m_p[m_nStart+(nNewLen-m_nBufferLen)]) , &(m_p[m_nStart]) , m_nBufferLen - m_nStart );
                m_nStart += nNewLen - m_nBufferLen;
            }
            m_nBufferLen = nNewLen;
        }
    }

    void MemRingBuffer::readAt( sal_Int32 nPos, Sequence<sal_Int8> &seq , sal_Int32 nBytesToRead ) const
    {
        if( nPos + nBytesToRead > m_nOccupiedBuffer ) {
            throw css::io::BufferSizeExceededException(
                "MemRingBuffer::readAt BufferSizeExceededException");
        }

        sal_Int32 nStartReadingPos = nPos + m_nStart;
        if( nStartReadingPos >= m_nBufferLen ) {
            nStartReadingPos -= m_nBufferLen;
        }

        seq.realloc( nBytesToRead );

        if( nStartReadingPos + nBytesToRead > m_nBufferLen ) {
            sal_Int32 nDeltaLen = m_nBufferLen - nStartReadingPos;
            memcpy( seq.getArray() , &(m_p[nStartReadingPos]) , nDeltaLen );
            memcpy( &(seq.getArray()[nDeltaLen]), m_p , nBytesToRead - nDeltaLen );
        }
        else {
            memcpy( seq.getArray() , &(m_p[nStartReadingPos]) , nBytesToRead );
        }
    }

    void MemRingBuffer::writeAt( sal_Int32 nPos, const Sequence<sal_Int8> &seq )
    {
        checkInvariants();
        sal_Int32 nLen = seq.getLength();

        if( nPos < 0 || nPos > std::numeric_limits< sal_Int32 >::max() - nLen )
        {
            throw css::io::BufferSizeExceededException(
                "MemRingBuffer::writeAt BufferSizeExceededException");
        }

        if( nPos + nLen - m_nOccupiedBuffer > 0 ) {
            resizeBuffer( nPos + seq.getLength() );
        }

        sal_Int32 nStartWritingIndex = m_nStart + nPos;
        if( nStartWritingIndex >= m_nBufferLen ) {
            nStartWritingIndex -= m_nBufferLen;
        }

        if( nLen + nStartWritingIndex > m_nBufferLen ) {
            // two area copy
            memcpy( &(m_p[nStartWritingIndex]) , seq.getConstArray(), m_nBufferLen-nStartWritingIndex );
            memcpy( m_p , &( seq.getConstArray()[m_nBufferLen-nStartWritingIndex] ),
                                            nLen - (m_nBufferLen-nStartWritingIndex) );

        }
        else {
            // one area copy
            memcpy( &( m_p[nStartWritingIndex]), seq.getConstArray() , nLen );
        }
        m_nOccupiedBuffer = std::max( nPos + seq.getLength() , m_nOccupiedBuffer );
        checkInvariants();
    }

    sal_Int32 MemRingBuffer::getSize()  const throw()
    {
        return m_nOccupiedBuffer;
    }

    void MemRingBuffer::forgetFromStart( sal_Int32 nBytesToForget )
    {
        checkInvariants();
        if( nBytesToForget > m_nOccupiedBuffer ) {
            throw css::io::BufferSizeExceededException(
                "MemRingBuffer::forgetFromStart BufferSizeExceededException");
        }
        m_nStart += nBytesToForget;
        if( m_nStart >= m_nBufferLen ) {
            m_nStart = m_nStart - m_nBufferLen;
        }
        m_nOccupiedBuffer -= nBytesToForget;
        checkInvariants();
    }

    }

    /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

↑ V701 realloc() possible leak: when realloc() fails in allocating memory, original pointer 'm_p' is lost. Consider assigning realloc() to a temporary pointer.