/* -*- 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 <limits>

#include <string.h>

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

#include <com/sun/star/io/BufferSizeExceededException.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_p(nullptr), m_nBufferLen(0), 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 )

        return;

    auto p = static_cast<sal_Int8*>(std::realloc(m_p, nNewLen));

    if (!p)

        throw css::io::BufferSizeExceededException(

            u"MemRingBuffer::resizeBuffer BufferSizeExceededException"_ustr);

    m_p = p;

    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(

            u"MemRingBuffer::readAt BufferSizeExceededException"_ustr);

    }

    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();

    const sal_Int32 nLen = seq.getLength();

    if( nPos < 0 || nPos > std::numeric_limits< sal_Int32 >::max() - nLen )

    {

        throw css::io::BufferSizeExceededException(

            u"MemRingBuffer::writeAt BufferSizeExceededException"_ustr);

    }

    if( nPos + nLen - m_nOccupiedBuffer > 0 ) {

        resizeBuffer( nPos + nLen );

        m_nOccupiedBuffer = nPos + nLen;

    }

    sal_Int32 nStartWritingIndex = m_nStart + nPos;

    if( nStartWritingIndex >= m_nBufferLen ) {

        nStartWritingIndex -= m_nBufferLen;

    }

    if( const sal_Int32 nBufferRestLen = m_nBufferLen-nStartWritingIndex; nLen > nBufferRestLen ) {

        // two area copy

        memcpy( &(m_p[nStartWritingIndex]) , seq.getConstArray(), nBufferRestLen );

        memcpy( m_p , &( seq.getConstArray()[nBufferRestLen] ), nLen - nBufferRestLen );

    }

    else {

        // one area copy

        memcpy( &( m_p[nStartWritingIndex]), seq.getConstArray() , nLen );

    }

    checkInvariants();

}

sal_Int32 MemRingBuffer::getSize()  const noexcept

{

    return m_nOccupiedBuffer;

}

void MemRingBuffer::forgetFromStart( sal_Int32 nBytesToForget )

{

    checkInvariants();

    if( nBytesToForget > m_nOccupiedBuffer ) {

        throw css::io::BufferSizeExceededException(

            u"MemRingBuffer::forgetFromStart BufferSizeExceededException"_ustr);

    }

    m_nStart += nBytesToForget;

    if( m_nStart >= m_nBufferLen ) {

        m_nStart = m_nStart - m_nBufferLen;

    }

    m_nOccupiedBuffer -= nBytesToForget;

    checkInvariants();

}

}

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