upiwin/src/msg_queue.c

#include <stdlib.h>
#include <pthread.h>
#include "wintype.h"
#include "time_func.h"
#include "msg_queue.h"

PMSG_QUEUE MqAlloc(int nentries)
{
  int sz = sizeof(MSG_QUEUE) + (nentries * sizeof(MSG));
  PMSG_QUEUE rc;

  rc = (PMSG_QUEUE)malloc(sz);
  if (!rc)
    return NULL;
  memset(rc, 0 sz);
  rc->startbound = &(rc->messagestore);
  rc->endbound = rc->startbound + nentries;
  rc->head = rc->tail = rc->startbound;
  rc->nentries = nentries;
  pthread_mutex_init(&(rc->mutex), NULL);
  return rc;
}

void MqDestroy(PMSG_QUEUE queue)
{
  pthread_mutex_destroy(&(queue->mutex));
  free(queue);
}

static void post_internal(PMSG_QUEUE queue, PMSG msg)
{
  PMSG nexttail;
  
  pthread_mutex_lock(&(queue->mutex));
  nexttail = queue->tail + 1;
  if (nexttail == queue->endbound)
    nexttail = queue->startbound;
  if (nexttail != queue->head)
  {
    memcpy(queue->tail, msg, sizeof(MSG));
    queue->tail = nexttail;
  }
  /* else drop the message silently */
  
  pthread_mutex_unlock(&(queue->mutex));
}

void MqPost(PMSG_QUEUE queue, uintptr_t target, unsigned message, const uintptr_t *attrs, int nattrs)
{
  MSG tmpmsg;

  memset(&tmpmsg, 0, sizeof(MSG));
  tmpmsg.target = target;
  tmpmsg.message = message;
  if (nattrs > MSG_ATTRCOUNT)
    nattrs = MSG_ATTRCOUNT;
  if (nattrs > 0)
    memcpy(&(tmpmsg.attrs), attrs, sizeof(uintptr_t) * nattrs);
  tmpmsg.timestamp = TimeSinceStart();
  post_internal(queue, &tmpmsg);
}

void MqPost1(PMSG_QUEUE queue, uintptr_t target, unsigned message, uintptr_t attr1)
{
  MSG tmpmsg;
  
  memset(&tmpmsg, 0, sizeof(MSG));
  tmpmsg.target = target;
  tmpmsg.message = message;
  tmpmsg.attrs[0] = attr1;
  tmpmsg.timestamp = TimeSinceStart();
  post_internal(queue, &tmpmsg);
}

int MqPeek(PMSG_QUEUE queue, PMSG msg, unsigned flags)
{
  int rc = 0;
  PMSG nexthead;
  
  pthread_mutex_lock(&(queue->mutex));
  if (queue->head != queue->tail)
  {
    nexthead = queue->head + 1;
    if (nexthead == queue->endbound)
      nexthead = queue->startbound;
    memcpy(msg, queue->head, sizeof(MSG));
    if (flags & PEEK_REMOVE)
      queue->head = nexthead;
  }
  pthread_mutex_unlock(&(queue->mutex));
  return rc;
}