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/*
Copyright (c) 2007-2009 FastMQ Inc.
This file is part of 0MQ.
0MQ is free software; you can redistribute it and/or modify it under
the terms of the Lesser GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
0MQ is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
Lesser GNU General Public License for more details.
You should have received a copy of the Lesser GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ZMQ_DECODER_HPP_INCLUDED__
#define __ZMQ_DECODER_HPP_INCLUDED__
#include <stddef.h>
#include <string.h>
#include <algorithm>
namespace zmq
{
// Helper base class for decoders that know the amount of data to read
// in advance at any moment. Knowing the amount in advance is a property
// of the protocol used. Both AMQP and backend protocol are based on
// size-prefixed paradigm, therefore they are using decoder_t to parse
// the messages. On the other hand, XML-based transports (like XMPP or
// SOAP) don't allow for knowing the size of data to read in advance and
// should use different decoding algorithms.
//
// Decoder implements the state machine that parses the incoming buffer.
// Derived class should implement individual state machine actions.
template <typename T> class decoder_t
{
public:
inline decoder_t () :
read_ptr (NULL),
to_read (0),
next (NULL)
{
}
// Push the binary data to the decoder. Returns number of bytes
// actually parsed.
inline size_t write (unsigned char *data_, size_t size_)
{
size_t pos = 0;
while (true) {
size_t to_copy = std::min (to_read, size_ - pos);
if (read_ptr) {
memcpy (read_ptr, data_ + pos, to_copy);
read_ptr += to_copy;
}
pos += to_copy;
to_read -= to_copy;
while (!to_read)
if (!(static_cast <T*> (this)->*next) ())
return pos;
if (pos == size_)
return pos;
}
}
protected:
// Prototype of state machine action. Action should return false if
// it is unable to push the data to the system.
typedef bool (T::*step_t) ();
// This function should be called from derived class to read data
// from the buffer and schedule next state machine action.
inline void next_step (void *read_ptr_, size_t to_read_,
step_t next_)
{
read_ptr = (unsigned char*) read_ptr_;
to_read = to_read_;
next = next_;
}
private:
unsigned char *read_ptr;
size_t to_read;
step_t next;
decoder_t (const decoder_t&);
void operator = (const decoder_t&);
};
}
#endif
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