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/*
Copyright (c) 2007-2010 iMatix Corporation
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_ENCODER_HPP_INCLUDED__
#define __ZMQ_ENCODER_HPP_INCLUDED__
#include "platform.hpp"
#if defined ZMQ_HAVE_WINDOWS
#include "windows.hpp"
#endif
#include <stddef.h>
#include <string.h>
#include <stdlib.h>
#include <algorithm>
#include "err.hpp"
namespace zmq
{
// Helper base class for encoders. It implements the state machine that
// fills the outgoing buffer. Derived classes should implement individual
// state machine actions.
template <typename T> class encoder_t
{
public:
inline encoder_t (size_t bufsize_) :
bufsize (bufsize_)
{
buf = (unsigned char*) malloc (bufsize_);
zmq_assert (buf);
}
inline ~encoder_t ()
{
free (buf);
}
// The function returns a batch of binary data. The data
// are filled to a supplied buffer. If no buffer is supplied (data_
// points to NULL) decoder object will provide buffer of its own.
// If offset is not NULL, it is filled by offset of the first message
// in the batch.If there's no beginning of a message in the batch,
// offset is set to -1.
inline void get_data (unsigned char **data_, size_t *size_,
int *offset_ = NULL)
{
unsigned char *buffer = !*data_ ? buf : *data_;
size_t buffersize = !*data_ ? bufsize : *size_;
size_t pos = 0;
if (offset_)
*offset_ = -1;
while (true) {
// If there are no more data to return, run the state machine.
// If there are still no data, return what we already have
// in the buffer.
if (!to_write) {
if (!(static_cast <T*> (this)->*next) ()) {
*data_ = buffer;
*size_ = pos;
return;
}
// If beginning of the message was processed, adjust the
// first-message-offset.
if (beginning) {
if (offset_ && *offset_ == -1)
*offset_ = pos;
beginning = false;
}
}
// If there are no data in the buffer yet and we are able to
// fill whole buffer in a single go, let's use zero-copy.
// There's no disadvantage to it as we cannot stuck multiple
// messages into the buffer anyway. Note that subsequent
// write(s) are non-blocking, thus each single write writes
// at most SO_SNDBUF bytes at once not depending on how large
// is the chunk returned from here.
// As a consequence, large messages being sent won't block
// other engines running in the same I/O thread for excessive
// amounts of time.
if (!pos && !*data_ && to_write >= buffersize) {
*data_ = write_pos;
*size_ = to_write;
write_pos = NULL;
to_write = 0;
return;
}
// Copy data to the buffer. If the buffer is full, return.
size_t to_copy = std::min (to_write, buffersize - pos);
memcpy (buffer + pos, write_pos, to_copy);
pos += to_copy;
write_pos += to_copy;
to_write -= to_copy;
if (pos == buffersize) {
*data_ = buffer;
*size_ = pos;
return;
}
}
}
protected:
// Prototype of state machine action.
typedef bool (T::*step_t) ();
// This function should be called from derived class to write the data
// to the buffer and schedule next state machine action. Set beginning
// to true when you are writing first byte of a message.
inline void next_step (void *write_pos_, size_t to_write_,
step_t next_, bool beginning_)
{
write_pos = (unsigned char*) write_pos_;
to_write = to_write_;
next = next_;
beginning = beginning_;
}
private:
unsigned char *write_pos;
size_t to_write;
step_t next;
bool beginning;
size_t bufsize;
unsigned char *buf;
encoder_t (const encoder_t&);
void operator = (const encoder_t&);
};
}
#endif
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