shared_mem_handle.h

#ifndef SHARED_MEM_HANDLER_H
#define SHARED_MEM_HANDLER_H

#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <time.h>

/* Shared memory support code */
static void randname(char* buf)
{
  struct timespec ts;
  clock_gettime(CLOCK_REALTIME, &ts);
  long r = ts.tv_nsec;
  for (int i = 0; i < 6; ++i)
  {
    buf[i] = 'A' + (r & 15) + (r & 16) * 2;
    r >>= 5;
  }
}

static int create_shm_file(void)
{
  int retries = 100;
  do
  {
    char name[] = "/wl_shm-XXXXXX";
    randname(name + sizeof(name) - 7);
    --retries;
    int fd = shm_open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
    if (fd >= 0)
    {
      shm_unlink(name);
      return fd;
    }
  } while (retries > 0 && errno == EEXIST);
  return -1;
}

static int allocate_shm_file(size_t size)
{
  int fd = create_shm_file();
  if (fd < 0)
    return -1;
  int ret;
  do
  {
    ret = ftruncate(fd, size);
  } while (ret < 0 && errno == EINTR);
  if (ret < 0)
  {
    close(fd);
    return -1;
  }
  return fd;
}

#endif