nix-vector.cc

Go to the documentation of this file.

/*
 * Copyright (c) 2009 The Georgia Institute of Technology
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Authors: Josh Pelkey <jpelkey@gatech.edu>
 */
 
#include "nix-vector.h"
 
#include "ns3/fatal-error.h"
#include "ns3/log.h"
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("NixVector");
 
typedef std::vector<uint32_t> NixBits_t; //!< typedef for the nixVector
 
NixVector::NixVector()
    : m_nixVector(0),
      m_used(0),
      m_totalBitSize(0),
      m_epoch(0)
{
    NS_LOG_FUNCTION(this);
}
 
NixVector::~NixVector()
{
    NS_LOG_FUNCTION(this);
}
 
NixVector::NixVector(const NixVector& o)
    : m_nixVector(o.m_nixVector),
      m_used(o.m_used),
      m_totalBitSize(o.m_totalBitSize),
      m_epoch(o.m_epoch)
{
}
 
NixVector&
NixVector::operator=(const NixVector& o)
{
    if (this == &o)
    {
        return *this;
    }
    m_nixVector = o.m_nixVector;
    m_used = o.m_used;
    m_totalBitSize = o.m_totalBitSize;
    m_epoch = o.m_epoch;
    return *this;
}
 
Ptr<NixVector>
NixVector::Copy() const
{
    NS_LOG_FUNCTION(this);
    // we need to invoke the copy constructor directly
    // rather than calling Create because the copy constructor
    // is private.
    return Ptr<NixVector>(new NixVector(*this), false);
}
 
/* For printing the nix vector */
std::ostream&
operator<<(std::ostream& os, const NixVector& nix)
{
    nix.DumpNixVector(os);
    os << " (" << nix.GetRemainingBits() << " bits left)";
    return os;
}
 
void
NixVector::AddNeighborIndex(uint32_t newBits, uint32_t numberOfBits)
{
    NS_LOG_FUNCTION(this << newBits << numberOfBits);
 
    if (numberOfBits > 32)
    {
        NS_FATAL_ERROR("Can't add more than 32 bits to a nix-vector at one time");
    }
 
    // This can be in the range [0,31]
    uint32_t currentVectorBitSize = m_totalBitSize % 32;
 
    if (currentVectorBitSize == 0)
    {
        m_nixVector.push_back(0);
    }
 
    // Check to see if the number
    // of new bits forces the creation of
    // a new entry into the NixVector vector
    // i.e., we will overflow int o.w.
    if (currentVectorBitSize + numberOfBits > 32)
    {
        // Put what we can in the remaining portion of the
        // vector entry
        uint32_t tempBits = newBits;
        tempBits = newBits << currentVectorBitSize;
        tempBits |= m_nixVector.back();
        m_nixVector.back() = tempBits;
 
        // Now start a new vector entry
        // and push the remaining bits
        // there
        newBits = newBits >> (32 - currentVectorBitSize);
        m_nixVector.push_back(newBits);
    }
    else
    {
        // Shift over the newbits by the
        // number of current bits.  This allows
        // us to logically OR with the present
        // NixVector, resulting in the new
        // NixVector
        newBits = newBits << currentVectorBitSize;
        newBits |= m_nixVector.back();
 
        // Now insert the new NixVector and
        // increment number of bits for
        // currentVectorBitSize and m_totalBitSize
        // accordingly
        m_nixVector.back() = newBits;
    }
    m_totalBitSize += numberOfBits;
}
 
uint32_t
NixVector::ExtractNeighborIndex(uint32_t numberOfBits)
{
    NS_LOG_FUNCTION(this << numberOfBits);
 
    if (numberOfBits > 32)
    {
        NS_FATAL_ERROR("Can't extract more than 32 bits to a nix-vector at one time");
    }
 
    uint32_t vectorIndex = 0;
    uint32_t extractedBits = 0;
    uint32_t totalRemainingBits = GetRemainingBits();
 
    if (numberOfBits > totalRemainingBits)
    {
        NS_FATAL_ERROR("You've tried to extract too many bits of the Nix-vector, "
                       << this << ". NumberBits: " << numberOfBits
                       << " Remaining: " << totalRemainingBits);
    }
 
    if (numberOfBits <= 0)
    {
        NS_FATAL_ERROR("You've specified a number of bits for Nix-vector <= 0!");
    }
 
    // First determine where in the NixVector
    // vector we need to extract which depends
    // on the number of used bits and the total
    // number of bits
    vectorIndex = ((totalRemainingBits - 1) / 32);
 
    // Next, determine if this extraction will
    // span multiple vector entries
    if (vectorIndex > 0) // we could span more than one
    {
        if ((numberOfBits - 1) > ((totalRemainingBits - 1) % 32)) // we do span more than one
        {
            extractedBits = m_nixVector.at(vectorIndex) << (32 - (totalRemainingBits % 32));
            extractedBits = extractedBits >> ((32 - (totalRemainingBits % 32)) -
                                              (numberOfBits - (totalRemainingBits % 32)));
            extractedBits |= (m_nixVector.at(vectorIndex - 1) >>
                              (32 - (numberOfBits - (totalRemainingBits % 32))));
            m_used += numberOfBits;
            return extractedBits;
        }
    }
 
    // we don't span more than one
    extractedBits = m_nixVector.at(vectorIndex) << (32 - (totalRemainingBits % 32));
    extractedBits = extractedBits >> (32 - (numberOfBits));
    m_used += numberOfBits;
    return extractedBits;
}
 
uint32_t
NixVector::GetSerializedSize() const
{
    NS_LOG_FUNCTION(this);
 
    if (m_totalBitSize == 0)
    {
        return sizeof(m_totalBitSize);
    }
 
    return sizeof(m_used) + sizeof(m_totalBitSize) + (sizeof(uint32_t) * m_nixVector.size()) +
           sizeof(m_epoch);
}
 
uint32_t
NixVector::Serialize(uint32_t* buffer, uint32_t maxSize) const
{
    NS_LOG_FUNCTION(this << buffer << maxSize);
    uint32_t* p = buffer;
 
    if (maxSize < GetSerializedSize())
    {
        return 0;
    }
 
    *p++ = m_totalBitSize;
 
    if (m_totalBitSize)
    {
        *p++ = m_used;
        for (uint32_t j = 0; j < m_nixVector.size(); j++)
        {
            *p++ = m_nixVector.at(j);
        }
        *p++ = m_epoch;
    }
 
    return 1;
}
 
uint32_t
NixVector::Deserialize(const uint32_t* buffer, uint32_t size)
{
    NS_LOG_FUNCTION(this << buffer << size);
    const uint32_t* p = buffer;
 
    NS_ASSERT_MSG(size >= sizeof(m_totalBitSize),
                  "NixVector minimum serialized length is " << sizeof(m_totalBitSize) << " bytes");
    if (size < sizeof(m_totalBitSize))
    {
        // return zero if an entire nix-vector was
        // not deserialized
        return 0;
    }
 
    m_totalBitSize = *p++;
 
    if (m_totalBitSize)
    {
        m_used = *p++;
 
        // NixVector is packed in 32-bit unsigned ints.
        uint32_t nixVectorLength = m_totalBitSize / 32;
        nixVectorLength += (m_totalBitSize % 32) ? 1 : 0;
 
        NS_ASSERT_MSG(size >= 16 + nixVectorLength,
                      "NixVector serialized length should have been " << 16 + nixVectorLength
                                                                      << " but buffer is shorter");
        if (size < 16 + nixVectorLength * 4)
        {
            // return zero if an entire nix-vector was
            // not deserialized
            return 0;
        }
 
        // make sure the nix-vector
        // is empty
        m_nixVector.clear();
        for (uint32_t j = 0; j < nixVectorLength; j++)
        {
            uint32_t nix = *p++;
            m_nixVector.push_back(nix);
        }
 
        m_epoch = *p++;
    }
 
    return GetSerializedSize();
}
 
void
NixVector::DumpNixVector(std::ostream& os) const
{
    NS_LOG_FUNCTION(this << &os);
 
    if (m_nixVector.empty())
    {
        os << "0";
        return;
    }
 
    std::vector<uint32_t>::const_reverse_iterator rIter;
    bool first = true;
 
    for (rIter = m_nixVector.rbegin(); rIter != m_nixVector.rend();)
    {
        if (m_totalBitSize % 32 != 0 && first)
        {
            PrintDec2BinNix(*rIter, m_totalBitSize % 32, os);
        }
        else
        {
            PrintDec2BinNix(*rIter, 32, os);
        }
        first = false;
 
        rIter++;
        if (rIter != m_nixVector.rend())
        {
            os << "--";
        }
    }
}
 
uint32_t
NixVector::GetRemainingBits() const
{
    NS_LOG_FUNCTION(this);
 
    return (m_totalBitSize - m_used);
}
 
uint32_t
NixVector::BitCount(uint32_t numberOfNeighbors) const
{
    NS_LOG_FUNCTION(this << numberOfNeighbors);
 
    // Given the numberOfNeighbors, return the number
    // of bits needed (essentially, log2(numberOfNeighbors-1)
    uint32_t bitCount = 0;
 
    if (numberOfNeighbors < 2)
    {
        return 1;
    }
    else
    {
        for (numberOfNeighbors -= 1; numberOfNeighbors != 0; numberOfNeighbors >>= 1)
        {
            bitCount++;
        }
        return bitCount;
    }
}
 
void
NixVector::PrintDec2BinNix(uint32_t decimalNum, uint32_t bitCount, std::ostream& os) const
{
    NS_LOG_FUNCTION(this << decimalNum << bitCount << &os);
    if (decimalNum == 0)
    {
        for (; bitCount > 0; bitCount--)
        {
            os << 0;
        }
        return;
    }
    if (decimalNum == 1)
    {
        for (; bitCount > 1; bitCount--)
        {
            os << 0;
        }
        os << 1;
    }
    else
    {
        PrintDec2BinNix(decimalNum / 2, bitCount - 1, os);
        os << decimalNum % 2;
    }
}
 
void
NixVector::SetEpoch(uint32_t epoch)
{
    m_epoch = epoch;
}
 
uint32_t
NixVector::GetEpoch() const
{
    return m_epoch;
}
 
} // namespace ns3