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Bramfeld Team 2015-08-31 14:01:44 +02:00
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/*
* Copyright (c) 2008-2011 Juli Mallett. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <common/buffer.h>
#include <common/endian.h>
#include <xcodec/xcodec.h>
#include <xcodec/xcodec_cache.h>
#include <xcodec/xcodec_decoder.h>
#include <xcodec/xcodec_encoder.h>
#include <xcodec/xcodec_hash.h>
////////////////////////////////////////////////////////////////////////////////
// //
// File: xcodec_decoder.cc //
// Description: decoding routines for the xcodex protocol //
// Project: WANProxy XTech //
// Adapted by: Andreu Vidal Bramfeld-Software //
// Last modified: 2015-08-31 //
// //
////////////////////////////////////////////////////////////////////////////////
XCodecDecoder::XCodecDecoder(XCodecCache* cache)
: log_("/xcodec/decoder"),
cache_(cache)
{ }
XCodecDecoder::~XCodecDecoder()
{ }
/*
* XXX These comments are out-of-date.
*
* Decode an XCodec-encoded stream. Returns false if there was an
* inconsistency, error or unrecoverable condition in the stream.
* Returns true if we were able to process the stream entirely or
* expect to be able to finish processing it once more data arrives.
* The input buffer is cleared of anything we can parse right now.
*
* Since some events later in the stream (i.e. ASK or LEARN) may need
* to be processed before some earlier in the stream (i.e. REF), we
* parse the stream into a list of actions to take, performing them
* as we go if possible, otherwise queueing them to occur until the
* action that is blocking the stream has been satisfied or the stream
* has been closed.
*
* XXX For now we will ASK in every stream where an unknown hash has
* occurred and expect a LEARN in all of them. In the future, it is
* desirable to optimize this. Especially once we start putting an
* instance UUID in the HELLO message and can tell which streams
* share an originator.
*/
bool
XCodecDecoder::decode (Buffer& output, Buffer& input, std::set<uint64_t>& unknown_hashes)
{
uint8_t data[XCODEC_SEGMENT_LENGTH];
Buffer old;
uint64_t behash;
uint64_t hash;
unsigned off;
uint8_t op;
while (! input.empty())
{
if (! input.find (XCODEC_MAGIC, &off))
{
input.moveout (&output);
break;
}
if (off > 0)
{
output.append (input, off);
input.skip (off);
}
ASSERT(log_, !input.empty());
/*
* Need the following byte at least.
*/
if (input.length() == 1)
break;
input.extract (&op, sizeof XCODEC_MAGIC);
switch (op)
{
case XCODEC_OP_ESCAPE:
output.append (XCODEC_MAGIC);
input.skip (sizeof XCODEC_MAGIC + sizeof op);
break;
case XCODEC_OP_EXTRACT:
if (input.length() < sizeof XCODEC_MAGIC + sizeof op + XCODEC_SEGMENT_LENGTH)
return (true);
input.skip (sizeof XCODEC_MAGIC + sizeof op);
input.copyout (data, XCODEC_SEGMENT_LENGTH);
hash = XCodecHash::hash (data);
if (cache_->lookup (hash, old))
{
if (old.equal (data, sizeof data))
{
DEBUG(log_) << "Declaring segment already in cache.";
}
else
{
ERROR(log_) << "Collision in <EXTRACT>.";
return (false);
}
old.clear ();
}
else
cache_->enter (hash, input, 0);
output.append (input, XCODEC_SEGMENT_LENGTH);
input.skip (XCODEC_SEGMENT_LENGTH);
break;
case XCODEC_OP_REF:
if (input.length() < sizeof XCODEC_MAGIC + sizeof op + sizeof behash)
return (true);
input.extract (&behash, sizeof XCODEC_MAGIC + sizeof op);
hash = BigEndian::decode (behash);
if (cache_->lookup (hash, output))
{
input.skip (sizeof XCODEC_MAGIC + sizeof op + sizeof behash);
}
else
{
if (unknown_hashes.find (hash) == unknown_hashes.end())
{
DEBUG(log_) << "Sending <ASK>, waiting for <LEARN>.";
unknown_hashes.insert (hash);
}
else
{
DEBUG(log_) << "Already sent <ASK>, waiting for <LEARN>.";
}
return (true);
}
break;
default:
ERROR(log_) << "Unsupported XCodec opcode " << (unsigned)op << ".";
return (false);
}
}
return (true);
}