Our Task object definition. As with message_queue.cpp, I've only commented the changes.
#include "task.h" #include "block.h" #include "data.h" Task::Task (void) : barrier_ (0) { ACE_DEBUG ((LM_DEBUG, "(%P|%t) Task ctor 0x%x\n", (void *) this)); } Task::~Task (void) { ACE_DEBUG ((LM_DEBUG, "(%P|%t) Task dtor 0x%x\n", (void *) this)); ACE_Message_Block *message; this->getq (message); message->release (); delete barrier_; } int Task::open (int threads) { barrier_ = new ACE_Barrier (threads); return this->activate (THR_NEW_LWP, threads); } int Task::close (u_long flags) { ACE_DEBUG ((LM_DEBUG, "(%P|%t) Task close 0x%x\n", (void *) this)); return inherited::close (flags); } int Task::svc (void) { this->barrier_->wait (); ACE_DEBUG ((LM_DEBUG, "(%P|%t) Task 0x%x starts in thread %d\n", (void *) this, ACE_Thread::self ())); ACE_Message_Block *message; while (1) { if (this->getq (message) == -1) { ACE_ERROR_RETURN ((LM_ERROR, "%p\n", "getq"), -1); } if (message->msg_type () == ACE_Message_Block::MB_HANGUP) { this->putq (message); break; } const char *cp = message->rd_ptr (); message->rd_ptr (strlen (cp) + 1); // Don't forget to skip the NULL we // inserted ACE_DEBUG ((LM_DEBUG, "(%P|%t) Block 0x%x contains (%s)\n", (void *) message, cp)); /* Create a Data object into which we can extract the message block contents. */ Data data; /* Use the rd_ptr() to access the message block data. Note that we've already moved it past the text string in the block. */ ACE_OS::memmove ((char *) &data, message->rd_ptr (), sizeof (data)); message->rd_ptr (sizeof (data)); // Move the rd_ptr() beyond the data. /* Invoke a couple of method calls on the object we constructed. */ data.who_am_i (); data.what_am_i (); /* An alternate approach: Data * data; data = (Data *)message->rd_ptr(); data->who_am_i(); data->what_am_i(); message->rd_ptr(sizeof(Data)); Even though this cuts down on the number of copies & constructions, I'm not real fond of it. You can get into trouble in a hurry by treating memory blocks as multiple data types... */ ACE_OS::sleep (ACE_Time_Value (0, 5000)); message->release (); } return (0); }
Notice how we had to create a temporary Data object to copy the stuff out of the message block? Again, if there were non-trivial ctor/dtors involved then this wouldn't work at all.