Node:Stream Example, Previous:Exceptions from C, Up:Mixing Examples

Stream Example

This is a small example how to initialize a bidirectional socket stream (error handling omitted):

typedef struct {
  int fd;                       /* socket number */
  FILE *r_stream;               /* For reading */
  FILE *w_stream;               /* For writing */
} SocketData;

int socket_sgetc(SocketData *socket)
{
  return fgetc(socket->r_stream);
}

int socket_sputc(char c, SocketData *socket)
{
  return fputc(c, socket->w_stream);
}

int socket_sflush(SocketData *socket)
{
  return fflush(socket->w_stream);
}

int socket_seof(SocketData *socket)
{
  return feof(socket->r_stream);
}

void socket_sclrerr(SocketData *socket)
{
  clearerr(socket->r_stream);
  clearerr(socket->w_stream);
}

int socket_sclose(SocketData *socket)
{
  fclose(socket->r_stream);
  fclose(socket->w_stream);
  close(socket->fd);
  free(socket);
  return 0;
}

SP_stream *new_socket_stream(int fd)
{
  SP_stream *stream;
  SocketData *socket;

/* Allocate and initialize data local to socket */

  socket = (SocketData *)malloc(sizeof(SocketData));
  socket->fd = fd;
  socket->r_stream = fdopen(fd,"r");
  socket->w_stream = fdopen(fd,"w");

/* Allocate and initialize Prolog stream */

  SP_make_stream(
                 socket,
                 socket_sgetc,
                 socket_sputc,
                 socket_sflush,
                 socket_seof,
                 socket_sclrerr,
                 socket_sclose,
                 &stream);

/* Allocate and copy string */

  stream->filename = "socket";
  stream->fd = fd;

  return stream;
}