buffer_rcv.cpp

#if ENABLE_NEW_RCVBUFFER
#include <cmath>
#include "buffer_rcv.h"
#include "logging.h"

using namespace std;

using namespace srt::sync;
using namespace srt_logging;
namespace srt_logging
{
    extern Logger brlog;
}
#define rbuflog brlog

namespace srt {

namespace {
    struct ScopedLog
    {
        ScopedLog() {};

        ~ScopedLog()
        {
            LOGC(rbuflog.Warn, log << ss.str());
        }

        stringstream ss;
    };

#define IF_RCVBUF_DEBUG(instr) (void)0

    // Check if iFirstNonreadPos is in range [iStartPos, (iStartPos + iMaxPosInc) % iSize].
    // The right edge is included because we expect iFirstNonreadPos to be
    // right after the last valid packet position if all packets are available.
    bool isInRange(int iStartPos, int iMaxPosInc, size_t iSize, int iFirstNonreadPos)
    {
        if (iFirstNonreadPos == iStartPos)
            return true;

        const int iLastPos = (iStartPos + iMaxPosInc) % iSize;
        const bool isOverrun = iLastPos < iStartPos;

        if (isOverrun)
            return iFirstNonreadPos > iStartPos || iFirstNonreadPos <= iLastPos;

        return iFirstNonreadPos > iStartPos && iFirstNonreadPos <= iLastPos;
    }
}


/*
 *   RcvBufferNew (circular buffer):
 *
 *   |<------------------- m_iSize ----------------------------->|
 *   |       |<----------- m_iMaxPosInc ------------>|           |
 *   |       |                                       |           |
 *   +---+---+---+---+---+---+---+---+---+---+---+---+---+   +---+
 *   | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 0 |...| 0 | m_pUnit[]
 *   +---+---+---+---+---+---+---+---+---+---+---+---+---+   +---+
 *             |                                   |
 *             |                                   |__last pkt received
 *             |___ m_iStartPos: first message to read
 *
 *   m_pUnit[i]->m_iFlag: 0:free, 1:good, 2:passack, 3:dropped
 *
 *   thread safety:
 *    m_iStartPos:   CUDT::m_RecvLock
 *    m_iLastAckPos: CUDT::m_AckLock
 *    m_iMaxPosInc:     none? (modified on add and ack
 */

CRcvBufferNew::CRcvBufferNew(int initSeqNo, size_t size, CUnitQueue* unitqueue, bool peerRexmit, bool bMessageAPI)
    : m_entries(size)
    , m_szSize(size) // TODO: maybe just use m_entries.size()
    , m_pUnitQueue(unitqueue)
    , m_iStartSeqNo(initSeqNo)
    , m_iStartPos(0)
    , m_iFirstNonreadPos(0)
    , m_iMaxPosInc(0)
    , m_iNotch(0)
    , m_numOutOfOrderPackets(0)
    , m_iFirstReadableOutOfOrder(-1)
    , m_bPeerRexmitFlag(peerRexmit)
    , m_bMessageAPI(bMessageAPI)
    , m_iBytesCount(0)
    , m_iPktsCount(0)
    , m_uAvgPayloadSz(SRT_LIVE_DEF_PLSIZE)
{
    SRT_ASSERT(size < INT_MAX); // All position pointers are integers
}

CRcvBufferNew::~CRcvBufferNew()
{
    for (size_t i = 0; i < m_szSize; ++i)
    {
        CUnit* unit = m_entries[i].pUnit;
        if (unit != NULL)
        {
            m_pUnitQueue->makeUnitFree(unit);
            m_entries[i].pUnit = NULL;
        }
    }
}

int CRcvBufferNew::insert(CUnit* unit)
{
    SRT_ASSERT(unit != NULL);
    const int32_t seqno  = unit->m_Packet.getSeqNo();
    const int     offset = CSeqNo::seqoff(m_iStartSeqNo, seqno);

    IF_RCVBUF_DEBUG(ScopedLog scoped_log);
    IF_RCVBUF_DEBUG(scoped_log.ss << "CRcvBufferNew::insert: seqno " << seqno << " m_iStartSeqNo " << m_iStartSeqNo << " offset " << offset);

    if (offset < 0)
    {
        IF_RCVBUF_DEBUG(scoped_log.ss << " returns -2");
        return -2;
    }

    if (offset >= (int)capacity())
    {
        IF_RCVBUF_DEBUG(scoped_log.ss << " returns -3");
        return -3;
    }

    // TODO: Don't do assert here. Process this situation somehow.
    // If >= 2, then probably there is a long gap, and buffer needs to be reset.
    SRT_ASSERT((m_iStartPos + offset) / m_szSize < 2);

    const int pos = (m_iStartPos + offset) % m_szSize;
    if (offset >= m_iMaxPosInc)
        m_iMaxPosInc = offset + 1;

    // Packet already exists
    SRT_ASSERT(pos >= 0 && pos < m_szSize);
    if (m_entries[pos].status != EntryState_Empty)
    {
        IF_RCVBUF_DEBUG(scoped_log.ss << " returns -1");
        return -1;
    }
    SRT_ASSERT(m_entries[pos].pUnit == NULL);

    m_pUnitQueue->makeUnitGood(unit);
    m_entries[pos].pUnit  = unit;
    m_entries[pos].status = EntryState_Avail;
    countBytes(1, (int)unit->m_Packet.getLength());

    // If packet "in order" flag is zero, it can be read out of order.
    // With TSBPD enabled packets are always assumed in order (the flag is ignored).
    if (!m_tsbpd.isEnabled() && m_bMessageAPI && !unit->m_Packet.getMsgOrderFlag())
    {
        ++m_numOutOfOrderPackets;
        onInsertNotInOrderPacket(pos);
    }

    updateNonreadPos();
    IF_RCVBUF_DEBUG(scoped_log.ss << " returns 0 (OK)");
    return 0;
}

int CRcvBufferNew::dropUpTo(int32_t seqno)
{
    // Can drop only when nothing to read, and 
    // first unacknowledged packet is missing.
    SRT_ASSERT(m_iStartPos == m_iFirstNonreadPos);

    IF_RCVBUF_DEBUG(ScopedLog scoped_log);
    IF_RCVBUF_DEBUG(scoped_log.ss << "CRcvBufferNew::dropUpTo: seqno " << seqno << " m_iStartSeqNo " << m_iStartSeqNo);

    int len = CSeqNo::seqoff(m_iStartSeqNo, seqno);
    SRT_ASSERT(len > 0);
    if (len <= 0)
    {
        IF_RCVBUF_DEBUG(scoped_log.ss << ". Nothing to drop.");
        return 0;
    }

    m_iMaxPosInc -= len;
    if (m_iMaxPosInc < 0)
        m_iMaxPosInc = 0;

    // Check that all packets being dropped are missing.
    const int iDropCnt = len;
    while (len > 0)
    {
        if (m_entries[m_iStartPos].pUnit != NULL)
        {
            releaseUnitInPos(m_iStartPos);
        }

        if (m_entries[m_iStartPos].status != EntryState_Empty)
        {
            SRT_ASSERT(m_entries[m_iStartPos].status == EntryState_Drop || m_entries[m_iStartPos].status == EntryState_Read);
            m_entries[m_iStartPos].status = EntryState_Empty;
        }

        SRT_ASSERT(m_entries[m_iStartPos].pUnit == NULL && m_entries[m_iStartPos].status == EntryState_Empty);
        m_iStartPos = incPos(m_iStartPos);
        --len;
    }

    // Update positions
    m_iStartSeqNo = seqno;
    // Move forward if there are "read" entries.
    releaseNextFillerEntries();
    // Set nonread position to the starting position before updating,
    // because start position was increased, and preceeding packets are invalid. 
    m_iFirstNonreadPos = m_iStartPos;
    updateNonreadPos();
    return iDropCnt;
}

void CRcvBufferNew::dropMessage(int32_t seqnolo, int32_t seqnohi, int32_t msgno)
{
    IF_RCVBUF_DEBUG(ScopedLog scoped_log);
    IF_RCVBUF_DEBUG(scoped_log.ss << "CRcvBufferNew::dropMessage: seqnolo " << seqnolo << " seqnohi " << seqnohi << " m_iStartSeqNo " << m_iStartSeqNo);
    // TODO: count bytes as removed?
    const int end_pos = incPos(m_iStartPos, m_iMaxPosInc);
    if (msgno != 0)
    {
        for (int i = m_iStartPos; i != end_pos; i = incPos(i))
        {
            // TODO: Maybe check status?
            if (!m_entries[i].pUnit)
                continue;

            const int32_t msgseq = m_entries[i].pUnit->m_Packet.getMsgSeq(m_bPeerRexmitFlag);
            if (msgseq == msgno)
            {
                releaseUnitInPos(i);
                m_entries[i].status = EntryState_Drop;
            }
        }

        return;
    }

    // Drop by packet seqno range.
    const int offset_a = CSeqNo::seqoff(m_iStartSeqNo, seqnolo);
    const int offset_b = CSeqNo::seqoff(m_iStartSeqNo, seqnohi);
    if (offset_b < 0)
    {
        LOGC(rbuflog.Warn, log << "CRcvBufferNew.dropMessage(): nothing to drop. Requested [" << seqnolo << "; "
                               << seqnohi << "]. Buffer start " << m_iStartSeqNo << ".");
        return;
    }

    const int start_off = max(0, offset_a);
    const int last_pos = incPos(m_iStartPos, offset_b);
    for (int i = incPos(m_iStartPos, start_off); i != end_pos && i != last_pos; i = incPos(i))
    {
        if (m_entries[i].pUnit)
        {
            releaseUnitInPos(i);
        }
        m_entries[i].status = EntryState_Drop;
    }

    LOGC(rbuflog.Debug, log << "CRcvBufferNew.dropMessage(): [" << seqnolo << "; "
        << seqnohi << "].");
}

int CRcvBufferNew::readMessage(char* data, size_t len, SRT_MSGCTRL* msgctrl)
{
    const bool canReadInOrder = hasReadableInorderPkts();
    if (!canReadInOrder && m_iFirstReadableOutOfOrder < 0)
    {
        LOGC(rbuflog.Warn, log << "CRcvBufferNew.readMessage(): nothing to read. Ignored isRcvDataReady() result?");
        return 0;
    }

    IF_RCVBUF_DEBUG(ScopedLog scoped_log);
    IF_RCVBUF_DEBUG(scoped_log.ss << "CRcvBufferNew::readMessage. m_iStartSeqNo " << m_iStartSeqNo);

    const int readPos = canReadInOrder ? m_iStartPos : m_iFirstReadableOutOfOrder;
    // Remember if we actually read out of order packet.
    const bool readingOutOfOrderPacket = !canReadInOrder || m_iStartPos == m_iFirstReadableOutOfOrder;

    size_t remain = len;
    char* dst = data;
    int    pkts_read = 0;
    int    bytes_extracted = 0; // The total number of bytes extracted from the buffer.
    const bool updateStartPos = (readPos == m_iStartPos); // Indicates if the m_iStartPos can be changed
    for (int i = readPos;; i = incPos(i))
    {
        SRT_ASSERT(m_entries[i].pUnit);
        if (!m_entries[i].pUnit)
        {
            LOGC(rbuflog.Error, log << "CRcvBufferNew::readMessage(): null packet encountered.");
            break;
        }

        const CPacket& packet  = m_entries[i].pUnit->m_Packet;
        const size_t   pktsize = packet.getLength();
        const int32_t pktseqno = packet.getSeqNo();

        // unitsize can be zero
        const size_t unitsize = std::min(remain, pktsize);
        memcpy(dst, packet.m_pcData, unitsize);
        remain -= unitsize;
        dst += unitsize;

        ++pkts_read;
        bytes_extracted += (int) pktsize;

        if (m_tsbpd.isEnabled())
            updateTsbPdTimeBase(packet.getMsgTimeStamp());

        if (m_numOutOfOrderPackets && !packet.getMsgOrderFlag())
            --m_numOutOfOrderPackets;

        const bool pbLast  = packet.getMsgBoundary() & PB_LAST;
        if (msgctrl && (packet.getMsgBoundary() & PB_FIRST))
        {
            msgctrl->pktseq = pktseqno;
            msgctrl->msgno  = packet.getMsgSeq(m_bPeerRexmitFlag);
        }
        if (msgctrl && pbLast)
        {
            msgctrl->srctime = count_microseconds(getPktTsbPdTime(packet.getMsgTimeStamp()).time_since_epoch());
        }

        releaseUnitInPos(i);
        if (updateStartPos)
        {
            m_iStartPos = incPos(i);
            --m_iMaxPosInc;
            SRT_ASSERT(m_iMaxPosInc >= 0);
            m_iStartSeqNo = CSeqNo::incseq(pktseqno);
        }
        else
        {
            // If out of order, only mark it read.
            m_entries[i].status = EntryState_Read;
        }

        if (pbLast)
        {
            if (readPos == m_iFirstReadableOutOfOrder)
                m_iFirstReadableOutOfOrder = -1;
            break;
        }
    }

    countBytes(-pkts_read, -bytes_extracted);
    if (!m_tsbpd.isEnabled() && readingOutOfOrderPacket)
        updateFirstReadableOutOfOrder();

    releaseNextFillerEntries();

    if (!isInRange(m_iStartPos, m_iMaxPosInc, m_szSize, m_iFirstNonreadPos))
    {
        m_iFirstNonreadPos = m_iStartPos;
        //updateNonreadPos();
    }

    const int bytes_read = dst - data;
    if (bytes_read < bytes_extracted)
    {
        LOGC(rbuflog.Error, log << "readMessage: small dst buffer, copied only " << bytes_read << "/" << bytes_extracted << " bytes.");
    }

    return bytes_read;
}

namespace {
    /// @brief Writes bytes to file stream.
    /// @param data pointer to data to write.
    /// @param len the number of bytes to write
    /// @param dst_offset ignored
    /// @param arg a void pointer to the fstream to write to.
    /// @return true on success, false on failure
    bool writeBytesToFile(char* data, int len, int dst_offset SRT_ATR_UNUSED, void* arg)
    {
        fstream* pofs = reinterpret_cast<fstream*>(arg);
        pofs->write(data, len);
        return !pofs->fail();
    }

    /// @brief Copies bytes to the destination buffer.
    /// @param data pointer to data to copy.
    /// @param len the number of bytes to copy
    /// @param dst_offset offset in destination buffer
    /// @param arg A pointer to the destination buffer
    /// @return true on success, false on failure
    bool copyBytesToBuf(char* data, int len, int dst_offset, void* arg)
    {
        char* dst = reinterpret_cast<char*>(arg) + dst_offset;
        memcpy(dst, data, len);
        return true;
    }
}

int CRcvBufferNew::readBufferTo(int len, copy_to_dst_f funcCopyToDst, void* arg)
{
    int p = m_iStartPos;
    const int end_pos = m_iFirstNonreadPos;

    const bool bTsbPdEnabled = m_tsbpd.isEnabled();
    const steady_clock::time_point now = (bTsbPdEnabled ? steady_clock::now() : steady_clock::time_point());

    int rs = len;
    while ((p != end_pos) && (rs > 0))
    {
        if (!m_entries[p].pUnit)
        {
            p = incPos(p);
            LOGC(rbuflog.Error, log << "readBufferTo: IPE: NULL unit found in file transmission");
            return -1;
        }

        const srt::CPacket& pkt = m_entries[p].pUnit->m_Packet;

        if (bTsbPdEnabled)
        {
            const steady_clock::time_point tsPlay = getPktTsbPdTime(pkt.getMsgTimeStamp());
            HLOGC(rbuflog.Debug,
                log << "readBuffer: check if time to play:"
                << " NOW=" << FormatTime(now)
                << " PKT TS=" << FormatTime(tsPlay));

            if ((tsPlay > now))
                break; /* too early for this unit, return whatever was copied */
        }

        const int pktlen = (int)pkt.getLength();
        const int remain_pktlen = pktlen - m_iNotch;
        const int unitsize = std::min(remain_pktlen, rs);

        if (!funcCopyToDst(pkt.m_pcData + m_iNotch, unitsize, len - rs, arg))
            break;

        if (rs >= remain_pktlen)
        {
            releaseUnitInPos(p);
            p = incPos(p);
            m_iNotch = 0;

            m_iStartPos = p;
            --m_iMaxPosInc;
            SRT_ASSERT(m_iMaxPosInc >= 0);
            m_iStartSeqNo = CSeqNo::incseq(m_iStartSeqNo);
        }
        else
            m_iNotch += rs;

        rs -= unitsize;
    }

    const int iBytesRead = len - rs;
    /* we removed acked bytes form receive buffer */
    countBytes(-1, -iBytesRead);

    // Update positions
    // Set nonread position to the starting position before updating,
    // because start position was increased, and preceeding packets are invalid. 
    if (!isInRange(m_iStartPos, m_iMaxPosInc, m_szSize, m_iFirstNonreadPos))
    {
        m_iFirstNonreadPos = m_iStartPos;
    }

    if (iBytesRead == 0)
    {
        LOGC(rbuflog.Error, log << "readBufferTo: 0 bytes read. m_iStartPos=" << m_iStartPos << ", m_iFirstNonreadPos=" << m_iFirstNonreadPos);
    }

    return iBytesRead;
}

int CRcvBufferNew::readBuffer(char* dst, int len)
{
    return readBufferTo(len, copyBytesToBuf, reinterpret_cast<void*>(dst));
}

int CRcvBufferNew::readBufferToFile(fstream& ofs, int len)
{
    return readBufferTo(len, writeBytesToFile, reinterpret_cast<void*>(&ofs));
}

bool CRcvBufferNew::hasAvailablePackets() const
{
    return hasReadableInorderPkts() || (m_numOutOfOrderPackets > 0 && m_iFirstReadableOutOfOrder != -1);
}

int CRcvBufferNew::getRcvDataSize() const
{
    if (m_iFirstNonreadPos >= m_iStartPos)
        return m_iFirstNonreadPos - m_iStartPos;

    return m_szSize + m_iFirstNonreadPos - m_iStartPos;
}

int CRcvBufferNew::getTimespan_ms() const
{
    if (!m_tsbpd.isEnabled())
        return 0;

    if (m_iMaxPosInc == 0)
        return 0;

    const int lastpos = incPos(m_iStartPos, m_iMaxPosInc - 1);
    int startpos = m_iStartPos;

    while (m_entries[startpos].pUnit == NULL)
    {
        if (startpos == lastpos)
            break;

        startpos = incPos(startpos);
    }

    if (m_entries[startpos].pUnit == NULL)
        return 0;

    // Should not happen
    SRT_ASSERT(m_entries[lastpos].pUnit != NULL);
    if (m_entries[lastpos].pUnit == NULL)
        return 0;

    const steady_clock::time_point startstamp =
        getPktTsbPdTime(m_entries[startpos].pUnit->m_Packet.getMsgTimeStamp());
    const steady_clock::time_point endstamp = getPktTsbPdTime(m_entries[lastpos].pUnit->m_Packet.getMsgTimeStamp());
    if (endstamp < startstamp)
        return 0;

    // One millisecond is added as a duration of a packet in the buffer.
    // If there is only one packet in the buffer, one millisecond is returned.
    return count_milliseconds(endstamp - startstamp) + 1;
}

int CRcvBufferNew::getRcvDataSize(int& bytes, int& timespan) const
{
    ScopedLock lck(m_BytesCountLock);
    bytes = m_iBytesCount;
    timespan = getTimespan_ms();
    return m_iPktsCount;
}

CRcvBufferNew::PacketInfo CRcvBufferNew::getFirstValidPacketInfo() const
{
    const int end_pos = incPos(m_iStartPos, m_iMaxPosInc);
    for (int i = m_iStartPos; i != end_pos; i = incPos(i))
    {
        // TODO: Maybe check status?
        if (!m_entries[i].pUnit)
            continue;

        const CPacket& packet = m_entries[i].pUnit->m_Packet;
        const PacketInfo info = { packet.getSeqNo(), i != m_iStartPos, getPktTsbPdTime(packet.getMsgTimeStamp()) };
        return info;
    }

    const PacketInfo info = { -1, false, time_point() };
    return info;
}

std::pair<int, int> CRcvBufferNew::getAvailablePacketsRange() const
{
    const int seqno_last = CSeqNo::incseq(m_iStartSeqNo, countReadable());
    return std::pair<int, int>(m_iStartSeqNo, seqno_last);
}

size_t CRcvBufferNew::countReadable() const
{
    if (m_iFirstNonreadPos >= m_iStartPos)
        return m_iFirstNonreadPos - m_iStartPos;
    return m_szSize + m_iFirstNonreadPos - m_iStartPos;
}

bool CRcvBufferNew::isRcvDataReady(time_point time_now) const
{
    const bool haveInorderPackets = hasReadableInorderPkts();
    if (!m_tsbpd.isEnabled())
    {
        if (haveInorderPackets)
            return true;

        SRT_ASSERT((!m_bMessageAPI && m_numOutOfOrderPackets == 0) || m_bMessageAPI);
        return (m_numOutOfOrderPackets > 0 && m_iFirstReadableOutOfOrder != -1);
    }

    if (!haveInorderPackets)
        return false;

    const PacketInfo info = getFirstValidPacketInfo();

    return info.tsbpd_time <= time_now;
}

void CRcvBufferNew::countBytes(int pkts, int bytes)
{
    ScopedLock lock(m_BytesCountLock);
    m_iBytesCount += bytes; // added or removed bytes from rcv buffer
    m_iPktsCount  += pkts;
    if (bytes > 0)          // Assuming one pkt when adding bytes
        m_uAvgPayloadSz = avg_iir<100>(m_uAvgPayloadSz, (unsigned) bytes);
}

void CRcvBufferNew::releaseUnitInPos(int pos)
{
    CUnit* tmp = m_entries[pos].pUnit;
    m_entries[pos] = Entry(); // pUnit = NULL; status = Empty
    if (tmp != NULL)
        m_pUnitQueue->makeUnitFree(tmp);
}

void CRcvBufferNew::releaseNextFillerEntries()
{
    int pos = m_iStartPos;
    while (m_entries[pos].status == EntryState_Read || m_entries[pos].status == EntryState_Drop)
    {
        m_iStartSeqNo = CSeqNo::incseq(m_iStartSeqNo);
        releaseUnitInPos(pos);
        pos = incPos(pos);
        m_iStartPos = pos;
    }
}

// TODO: Is this function complete? There are some comments left inside.
void CRcvBufferNew::updateNonreadPos()
{
    if (m_iMaxPosInc == 0)
        return;

    const int end_pos = incPos(m_iStartPos, m_iMaxPosInc); // The empty position right after the last valid entry.

    int pos = m_iFirstNonreadPos;
    while (m_entries[pos].pUnit && m_entries[pos].status == EntryState_Avail)
    {
        if (m_bMessageAPI && (m_entries[pos].pUnit->m_Packet.getMsgBoundary() & PB_FIRST) == 0)
            break;

        for (int i = pos; i != end_pos; i = incPos(i))
        {
            if (!m_entries[i].pUnit || m_entries[pos].status != EntryState_Avail)
            {
                break;
            }

            // Check PB_LAST only in message mode.
            if (!m_bMessageAPI || m_entries[i].pUnit->m_Packet.getMsgBoundary() & PB_LAST)
            {
                m_iFirstNonreadPos = incPos(i);
                break;
            }
        }

        if (pos == m_iFirstNonreadPos || !m_entries[m_iFirstNonreadPos].pUnit)
            break;

        pos = m_iFirstNonreadPos;
    }
}

int CRcvBufferNew::findLastMessagePkt()
{
    for (int i = m_iStartPos; i != m_iFirstNonreadPos; i = incPos(i))
    {
        SRT_ASSERT(m_entries[i].pUnit);

        if (m_entries[i].pUnit->m_Packet.getMsgBoundary() & PB_LAST)
        {
            return i;
        }
    }

    return -1;
}

void CRcvBufferNew::onInsertNotInOrderPacket(int insertPos)
{
    if (m_numOutOfOrderPackets == 0)
        return;

    // If the following condition is true, there is already a packet,
    // that can be read out of order. We don't need to search for
    // another one. The search should be done when that packet is read out from the buffer.
    //
    // There might happen that the packet being added precedes the previously found one.
    // However, it is allowed to re bead out of order, so no need to update the position.
    if (m_iFirstReadableOutOfOrder >= 0)
        return;

    // Just a sanity check. This function is called when a new packet is added.
    // So the should be unacknowledged packets.
    SRT_ASSERT(m_iMaxPosInc > 0);
    SRT_ASSERT(m_entries[insertPos].pUnit);
    const CPacket& pkt = m_entries[insertPos].pUnit->m_Packet;
    const PacketBoundary boundary = pkt.getMsgBoundary();

    //if ((boundary & PB_FIRST) && (boundary & PB_LAST))
    //{
    //    // This packet can be read out of order
    //    m_iFirstReadableOutOfOrder = insertPos;
    //    return;
    //}

    const int msgNo = pkt.getMsgSeq(m_bPeerRexmitFlag);
    // First check last packet, because it is expected to be received last.
    const bool hasLast = (boundary & PB_LAST) || (-1 < scanNotInOrderMessageRight(insertPos, msgNo));
    if (!hasLast)
        return;

    const int firstPktPos = (boundary & PB_FIRST)
        ? insertPos
        : scanNotInOrderMessageLeft(insertPos, msgNo);
    if (firstPktPos < 0)
        return;

    m_iFirstReadableOutOfOrder = firstPktPos;
    return;
}

void CRcvBufferNew::updateFirstReadableOutOfOrder()
{
    if (hasReadableInorderPkts() || m_numOutOfOrderPackets <= 0 || m_iFirstReadableOutOfOrder >= 0)
        return;

    if (m_iMaxPosInc == 0)
        return;

    // TODO: unused variable outOfOrderPktsRemain?
    int outOfOrderPktsRemain = m_numOutOfOrderPackets;

    // Search further packets to the right.
    // First check if there are packets to the right.
    const int lastPos = (m_iStartPos + m_iMaxPosInc - 1) % m_szSize;

    int posFirst = -1;
    int posLast = -1;
    int msgNo = -1;

    for (int pos = m_iStartPos; outOfOrderPktsRemain; pos = incPos(pos))
    {
        if (!m_entries[pos].pUnit)
        {
            posFirst = posLast = msgNo = -1;
            continue;
        }

        const CPacket& pkt = m_entries[pos].pUnit->m_Packet;

        if (pkt.getMsgOrderFlag())   // Skip in order packet
        {
            posFirst = posLast = msgNo = -1;
            continue;
        }

        --outOfOrderPktsRemain;

        const PacketBoundary boundary = pkt.getMsgBoundary();
        if (boundary & PB_FIRST)
        {
            posFirst = pos;
            msgNo = pkt.getMsgSeq(m_bPeerRexmitFlag);
        }

        if (pkt.getMsgSeq(m_bPeerRexmitFlag) != msgNo)
        {
            posFirst = posLast = msgNo = -1;
            continue;
        }

        if (boundary & PB_LAST)
        {
            m_iFirstReadableOutOfOrder = posFirst;
            return;
        }

        if (pos == lastPos)
            break;
    }

    return;
}

int CRcvBufferNew::scanNotInOrderMessageRight(const int startPos, int msgNo) const
{
    // Search further packets to the right.
    // First check if there are packets to the right.
    const int lastPos = (m_iStartPos + m_iMaxPosInc - 1) % m_szSize;
    if (startPos == lastPos)
        return -1;

    int pos = startPos;
    do
    {
        pos = incPos(pos);
        if (!m_entries[pos].pUnit)
            break;

        const CPacket& pkt = m_entries[pos].pUnit->m_Packet;

        if (pkt.getMsgSeq(m_bPeerRexmitFlag) != msgNo)
        {
            LOGC(rbuflog.Error, log << "Missing PB_LAST packet for msgNo " << msgNo);
            return -1;
        }

        const PacketBoundary boundary = pkt.getMsgBoundary();
        if (boundary & PB_LAST)
            return pos;
    } while (pos != lastPos);

    return -1;
}

int CRcvBufferNew::scanNotInOrderMessageLeft(const int startPos, int msgNo) const
{
    // Search preceeding packets to the left.
    // First check if there are packets to the left.
    if (startPos == m_iStartPos)
        return -1;

    int pos = startPos;
    do
    {
        pos = decPos(pos);

        if (!m_entries[pos].pUnit)
            return -1;

        const CPacket& pkt = m_entries[pos].pUnit->m_Packet;

        if (pkt.getMsgSeq(m_bPeerRexmitFlag) != msgNo)
        {
            LOGC(rbuflog.Error, log << "Missing PB_FIRST packet for msgNo " << msgNo);
            return -1;
        }

        const PacketBoundary boundary = pkt.getMsgBoundary();
        if (boundary & PB_FIRST)
            return pos;
    } while (pos != m_iStartPos);

    return -1;
}

bool CRcvBufferNew::addRcvTsbPdDriftSample(uint32_t usTimestamp, int usRTTSample)
{
    return m_tsbpd.addDriftSample(usTimestamp, usRTTSample);
}

void CRcvBufferNew::setTsbPdMode(const steady_clock::time_point& timebase, bool wrap, duration delay)
{
    m_tsbpd.setTsbPdMode(timebase, wrap, delay);
}

void CRcvBufferNew::applyGroupTime(const steady_clock::time_point& timebase,
    bool                            wrp,
    uint32_t                        delay,
    const steady_clock::duration& udrift)
{
    m_tsbpd.applyGroupTime(timebase, wrp, delay, udrift);
}

void CRcvBufferNew::applyGroupDrift(const steady_clock::time_point& timebase,
    bool                            wrp,
    const steady_clock::duration& udrift)
{
    m_tsbpd.applyGroupDrift(timebase, wrp, udrift);
}

CRcvBufferNew::time_point CRcvBufferNew::getTsbPdTimeBase(uint32_t usPktTimestamp) const
{
    return m_tsbpd.getTsbPdTimeBase(usPktTimestamp);
}

void CRcvBufferNew::updateTsbPdTimeBase(uint32_t usPktTimestamp)
{
    m_tsbpd.updateTsbPdTimeBase(usPktTimestamp);
}

string CRcvBufferNew::strFullnessState(int iFirstUnackSeqNo, const time_point& tsNow) const
{
    stringstream ss;

    ss << "Space avail " << getAvailSize(iFirstUnackSeqNo) << "/" << m_szSize;
    ss << " pkts. ";
    if (m_tsbpd.isEnabled() && m_iMaxPosInc > 0)
    {
        ss << " (TSBPD ready in ";
        if (m_entries[m_iStartPos].pUnit)
        {
            const uint32_t usPktTimestamp = m_entries[m_iStartPos].pUnit->m_Packet.getMsgTimeStamp();
            ss << count_milliseconds(m_tsbpd.getPktTsbPdTime(usPktTimestamp) - tsNow);
        }
        else
        {
            ss << "n/a";
        }

        const int iLastPos = incPos(m_iStartPos, m_iMaxPosInc - 1);
        if (m_entries[iLastPos].pUnit)
        {
            ss << ":";
            const uint32_t usPktTimestamp = m_entries[m_iStartPos].pUnit->m_Packet.getMsgTimeStamp();
            ss << count_milliseconds(m_tsbpd.getPktTsbPdTime(usPktTimestamp) - tsNow);
            ss << " ms";
        }
        else
        {
            ss << ":n/a ms";
        }
        ss << ". ";
    }

    ss << SRT_SYNC_CLOCK_STR " drift " << getDrift() / 1000 << " ms.";
    return ss.str();
}

CRcvBufferNew::time_point CRcvBufferNew::getPktTsbPdTime(uint32_t usPktTimestamp) const
{
    return m_tsbpd.getPktTsbPdTime(usPktTimestamp);
}

/* Return moving average of acked data pkts, bytes, and timespan (ms) of the receive buffer */
int CRcvBufferNew::getRcvAvgDataSize(int& bytes, int& timespan)
{
    // Average number of packets and timespan could be small,
    // so rounding is beneficial, while for the number of
    // bytes in the buffer is a higher value, so rounding can be omitted,
    // but probably better to round all three values.
    timespan = static_cast<int>(round((m_mavg.timespan_ms())));
    bytes = static_cast<int>(round((m_mavg.bytes())));
    return static_cast<int>(round(m_mavg.pkts()));
}

/* Update moving average of acked data pkts, bytes, and timespan (ms) of the receive buffer */
void CRcvBufferNew::updRcvAvgDataSize(const steady_clock::time_point& now)
{
    if (!m_mavg.isTimeToUpdate(now))
        return;

    int       bytes = 0;
    int       timespan_ms = 0;
    const int pkts = getRcvDataSize(bytes, timespan_ms);
    m_mavg.update(now, pkts, bytes, timespan_ms);
}

} // namespace srt

#endif // ENABLE_NEW_RCVBUFFER