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// $Id$
#ifndef ACE_RMCAST_FRAGMENT_C
#define ACE_RMCAST_FRAGMENT_C
#include "RMCast_Fragment.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#if !defined (__ACE_INLINE__)
#include "RMCast_Fragment.i"
#endif /* __ACE_INLINE__ */
ACE_RCSID(ace, RMCast_Fragment, "$Id$")
template <ACE_SYNCH_DECL>
ACE_RMCast_Fragment<ACE_SYNCH_USE>::
ACE_RMCast_Fragment (ACE_Thread_Manager *thr_mgr,
ACE_Message_Queue<ACE_SYNCH_USE> *mq)
: ACE_Task<ACE_SYNCH_USE> (thr_mgr, mq)
, max_fragment_size_ (ACE_RMCAST_DEFAULT_FRAGMENT_SIZE)
{
}
template <ACE_SYNCH_DECL>
ACE_RMCast_Fragment<ACE_SYNCH_USE>::
~ACE_RMCast_Fragment (void)
{
}
template <ACE_SYNCH_DECL> int
ACE_RMCast_Fragment<ACE_SYNCH_USE>::put (ACE_Message_Block *mb,
ACE_Time_Value *tv)
{
// @@ We should keep the total size precomputed
size_t total_size = mb->total_size ();
#if defined (ACE_HAS_BROKEN_DGRAM_SENDV)
const int TAO_WRITEV_MAX = IOV_MAX - 1;
#else
const int TAO_WRITEV_MAX = IOV_MAX;
#endif /* ACE_HAS_BROKEN_DGRAM_SENDV */
const size_t max_fragment_payload = this->max_fragment_size_;
// Iterate over all the message blocks in the chain. If there is
// enough data to send an MTU then it is sent immediately.
// The last fragment is sent with whatever data remains.
// A single fragment can expand multiple message blocks, put
// together in an <iovec> array, it is also possible that a single
// message block requires multiple fragments... so the code below is
// as simple as possible, but not any simpler ;-)
// The first piece of each fragment is a header that contains:
// - A sequence number for reassembly, this is unrelated to
// the sequence number for re-transmission.
// NOTE: yes, this increases the bandwidth requires by 4 bytes on
// each message, I don't think this is a big deal.
// - A fragment offset for reassembly.
// - The total size of the message, so the reassembly layer knows
// when a complete message has been received.
ACE_UINT32 message_sequence_number;
ACE_UINT32 fragment_offset = 0;
{
ACE_GUARD_RETURN (ACE_SYNCH_MUTEX_T, ace_mon, this->mutex_, -1);
message_sequence_number = ++(this->sequence_number_generator_);
}
// The underlying transport layer can only tolerate so many elements
// in a chain, so we must count them and send a fragment if we are
// going over the limit.
ACE_Message_Block blocks[TAO_WRITEV_MAX];
// The first message block contains the fragmentation layer
// header...
ACE_UINT32 header[3];
header[0] = ACE_HTONL(message_sequence_number);
header[1] = ACE_HTONL(fragment_offset);
header[2] = ACE_HTONL(total_size);
const size_t fragment_header_size = sizeof(header);
blocks[0].init (ACE_reinterpret_cast(char*,header),
fragment_header_size);
blocks[0].wr_ptr (fragment_header_size);
// How many elements of the <blocks> array are in use...
int iovcnt = 1;
// The size of the current message, adding the size of all its
// message blocks.
size_t fragment_size = fragment_header_size;
for (ACE_Message_Block* b = mb; b != 0; b = b->cont ())
{
// Add the block to the vector...
ACE_Message_Block *last_block = blocks + iovcnt;
last_block->data_block (b->data_block ()->duplicate ());
last_block->rd_ptr (b->rd_ptr ());
last_block->wr_ptr (b->wr_ptr ());
last_block->cont (0);
// Set the continuation field
blocks[iovcnt - 1].cont (last_block);
size_t last_block_length = last_block->length ();
// Recompute the state of the fragment
fragment_size += last_block_length;
iovcnt++;
while (fragment_size >= max_fragment_payload)
{
// We have filled a fragment. It is possible that we need
// to split the last message block in multiple fragments,
// thus the loop above...
// First adjust the last message block to exactly fit in the
// fragment:
size_t last_sent_mb_len =
max_fragment_payload - (fragment_size - last_block_length);
// Send only enough data of the last message block to fill
// the fragment...
last_block->wr_ptr (last_block->rd_ptr ()
+ last_sent_mb_len);
if (this->put_next (blocks, tv) == -1)
return -1;
// adjust the offset
fragment_offset += max_fragment_payload - fragment_header_size;
header[1] = ACE_HTONL(fragment_offset);
// Now compute how much data is left in the last message
// block, to check if we should continue sending it...
last_block_length -= last_sent_mb_len;
if (last_block_length == 0)
{
// No more data from this message block, just continue
// the outer loop...
iovcnt = 1;
fragment_size = fragment_header_size;
blocks[0].cont (0);
break; // while
}
// There is some data left, we try to send it in a single
// fragment, if it is still too big the beginning of this
// loop will adjust things.
// We must put the data in the right place in the array..
char *rd_ptr = last_block->rd_ptr () + last_sent_mb_len;
char *wr_ptr = rd_ptr + last_block_length;
blocks[1].data_block (last_block->replace_data_block (0));
// And determine what segment of the data will be sent..
blocks[1].rd_ptr (rd_ptr);
blocks[1].wr_ptr (wr_ptr);
blocks[1].cont (0);
last_block = &blocks[1];
// Setup the cont field...
blocks[0].cont (last_block);
// Adjust the state of the fragment
fragment_size = last_block_length + fragment_header_size;
iovcnt = 2;
// Notice that if <fragment_size> is too big the start of
// this loop will continue the fragmentation.
}
// It is also possible to fill up the iovec array before the
// fragment is completed, in this case we must send whatever we
// have:
if (iovcnt == TAO_WRITEV_MAX)
{
if (this->put_next (blocks, tv) == -1)
return -1;
fragment_offset += fragment_size - fragment_header_size;
header[1] = ACE_HTONL(fragment_offset);
iovcnt = 1;
fragment_size = fragment_header_size;
blocks[0].cont (0);
}
}
if (iovcnt == 1)
return 0;
return this->put_next (blocks, tv);
}
#endif /* ACE_RMCAST_FRAGMENT_C */
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