inet::ReassemblyBuffer Class Reference

Generic reassembly buffer for a fragmented datagram (or a fragmented anything). More...

#include <ReassemblyBuffer.h>

Classes
struct	Region

Public Member Functions
	ReassemblyBuffer ()
	Ctor. More...
	~ReassemblyBuffer ()
	Dtor. More...
bool	addFragment (ushort beg, ushort end, bool islast)
	Add a fragment, and returns true if reassembly has completed (i.e. More...
ushort	getTotalLength () const
	Returns the total (assembled) length of the datagram. More...

Protected Types
typedef std::vector< Region >	RegionVector

Protected Member Functions
void	merge (ushort beg, ushort end, bool islast)
void	mergeFragments ()

Protected Attributes
Region	main
RegionVector *	fragments

Detailed Description

Generic reassembly buffer for a fragmented datagram (or a fragmented anything).

Currently used in IPv4FragBuf and IPv6FragBuf.

Member Typedef Documentation

typedef std::vector<Region> inet::ReassemblyBuffer::RegionVector

protected

Constructor & Destructor Documentation

inet::ReassemblyBuffer::ReassemblyBuffer

(

)

Ctor.

{
    main.beg = main.end = 0;
    main.islast = false;
    fragments = nullptr;
}

inet::ReassemblyBuffer::~ReassemblyBuffer

(

)

Dtor.

{
    delete fragments;
}

Member Function Documentation

bool inet::ReassemblyBuffer::addFragment	(	ushort	beg,
		ushort	end,
		bool	islast
	)

Add a fragment, and returns true if reassembly has completed (i.e.

we have everything from offset 0 to the last fragment).

Referenced by inet::IPv4FragBuf::addFragment(), and inet::IPv6FragBuf::addFragment().

{
    merge(beg, end, islast);

    // do we have the complete datagram?
    return main.beg == 0 && main.islast;
}

ushort inet::ReassemblyBuffer::getTotalLength ( ) const

inline

Returns the total (assembled) length of the datagram.

Can only be called after addFragment() returned true.

Referenced by inet::IPv4FragBuf::addFragment(), and inet::IPv6FragBuf::addFragment().

{ return main.end; }

void inet::ReassemblyBuffer::merge ( ushort  beg, ushort  end, bool  islast  )

protected

Referenced by addFragment().

{
    if (main.end == beg) {
        // most typical case (<95%): new fragment follows last one
        main.end = end;
        if (islast)
            main.islast = true;
        if (fragments)
            mergeFragments();
    }
    else if (main.beg == end) {
        // new fragment precedes what we already have
        main.beg = beg;
        if (fragments)
            mergeFragments();
    }
    else if (main.end < beg || main.beg > end) {
        // disjoint fragment, store it until another fragment fills in the gap
        if (!fragments)
            fragments = new RegionVector();
        Region r;
        r.beg = beg;
        r.end = end;
        r.islast = islast;
        fragments->push_back(r);
    }
    else {
        // overlapping is not possible;
        // fragment's range already contained in buffer (probably duplicate fragment)
    }
}

void inet::ReassemblyBuffer::mergeFragments ( )

protected

Referenced by merge().

{
    RegionVector& frags = *fragments;

    bool oncemore;
    do {
        oncemore = false;
        for (auto i = frags.begin(); i != frags.end(); ) {
            bool deleteit = false;
            Region& frag = *i;
            if (main.end == frag.beg) {
                main.end = frag.end;
                if (frag.islast)
                    main.islast = true;
                deleteit = true;
            }
            else if (main.beg == frag.end) {
                main.beg = frag.beg;
                deleteit = true;
            }
            else if (main.beg <= frag.beg && main.end >= frag.end) {
                // we already have this region (duplicate fragment), delete it
                deleteit = true;
            }

            if (deleteit) {
                // deletion is tricky because erase() invalidates iterator
                int pos = i - frags.begin();
                frags.erase(i);
                i = frags.begin() + pos;
                oncemore = true;
            }
            else {
                ++i;
            }
        }
    } while (oncemore);
}

Member Data Documentation

RegionVector* inet::ReassemblyBuffer::fragments

protected

Referenced by merge(), mergeFragments(), ReassemblyBuffer(), and ~ReassemblyBuffer().

Region inet::ReassemblyBuffer::main

protected

Referenced by addFragment(), merge(), mergeFragments(), and ReassemblyBuffer().

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The documentation for this class was generated from the following files:

• ReassemblyBuffer.h
• ReassemblyBuffer.cc