Multithreaded erlang port drivers

gistfile1.txt

/* This is a skeleton to show how to make multithreaded erlang port drivers */
/* This programme requires erl_comm.c from the standard erlang distribution */
/* setup, shutdown and handle_port_messages are device specific */
/* setup is expected to open device file for reading */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>     /* pthread functions and data structures */

static pthread_mutex_t mtx_write_port = PTHREAD_MUTEX_INITIALIZER;
int write_port(void *data, int Size)
{
  /* write port has mutex to allows recv_thread and main_thread
  to both be able to write to the erlang port without interfering
  with each other */
  pthread_mutex_lock(&mtx_write_port);
  write_cmd(1,data,Size);
  pthread_mutex_unlock(&mtx_write_port);
}

void recv_thread(t_state *state)
{
  fd = state->fd;
  struct
    {
      char prefix[5];
      struct DEVICE_MSG data;
    } event;
  strcpy(event.prefix,"dev");
  
/* note: need to put timeout on device read in otherwise shutdown_flag
may not read if device is not responding */

while (shutdown_flag == 0)
{
    if (read(fd, &event.data, sizeof(event.data))== sizeof(event.data)
    	write_port(&event,sizeof(event));
    else
      exit(INVALID_DEVICE_DATA);
}

int main(int argc, char **argv)
{
  char *filename = argv[1];
  int shutdown_flag = 0;
  setup(&state,filename);
  pthread_t thread_id;
  pthread_create(&thread_id, NULL, recv_thread, (void*)&state);
  handle_port_messages();
  shutdown_flag++;
  pthread_join(thread_id,NULL),
  cleanup(&state);
  return 0;
  }