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