queue_create

SMT
Version 2.81

`queue_create`

#include "smtlib.h"
QUEUE *
queue_create (
    AGENT *agent,                       /*  Parent agent block, or null      */
    int    max_events                   /*  Max. events; 0 = no limit        */
)

Synopsis

Creates an event queue, and returns a handle to the created queue. Event queues are unnamed but attached to a agent within an agent. Queue can also be 'floating', i.e. not attached to a agent. This is useful for foreign programs. If you specify a agent, the queue is attached to that agent. If the agent argument is null, the queue is left floating. You always refer to a queue using its address (within the owning process) or QID handle (within any process). The current implementation uses a linked list in heap memory, so QID handles are only valid within the process. Future implementations may use other types of shared memory including connections across a communications protocol. Returns a pointer to the created QUEUE block. In case of error, returns null and sets smt_errno to one of these values:

SMT NOTREADY smt_init() was not called, or failed
SMT OUTOFMEMORY Not enough heap memory left

Source Code - (smtlib.c)

{
    static
      long  top_id = 0;                 /*  We number queues from 1 up       */
    QID     qid;                        /*  Created queue                    */
    SYMBOL  *dict_entry;                /*  Dictionary symbol                */
    QUEUE   *queue;                     /*  Queue information block          */

#if (defined (SMT_TRACE))
    trace ("queue_create: agent=%s", agent? agent-> name: "<none>");
#endif
    if (!smt_alive)                     /*  If SMT API was not correctly     */
      {                                 /*    initialised, forget it         */
        smt_errno = SMT_NOTREADY;
        return (NULL);
      }

    qid.node  = 0;                      /*  Queues are local for now         */
    qid.ident = ++top_id;               /*  First queue has id = 1           */
    dict_entry = sym_create_symbol (dict, get_queue_name (&qid), NULL);
    if (dict_entry == NULL)
      {
        smt_errno = SMT_OUTOFMEMORY;
        return (NULL);
      }

    /*  Allocate a QUEUE block and attach it to the queue list               */
    queue = (QUEUE *) node_create (agent? &agent-> queues: NULL,
                                   sizeof (QUEUE));
    if (queue == NULL)
      {
        sym_delete_symbol (dict, dict_entry);
        smt_errno = SMT_OUTOFMEMORY;
        return (NULL);
      }

    /*  Point the dictionary entry to the queue information block            */
    dict_entry-> data = queue;

    /*  Now initialise the queue info block fields and list heads            */
    node_reset (&queue-> events);
    node_reset (&queue-> threads);
    queue-> symbol     = dict_entry;
    queue-> agent      = agent;
    queue-> qid        = qid;
    queue-> max_events = max_events;
    queue-> shutdown   = FALSE;
    return (queue);
}

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SMT NOTREADY	smt_init() was not called, or failed
SMT OUTOFMEMORY	Not enough heap memory left