Changed license terms to the plain LGPL thru-out.

[bpt/guile.git] / libguile / ports.c

/* Copyright (C) 1995,1996,1997,1998,1999,2000,2001 Free Software Foundation, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */


\f
/* Headers.  */

#if HAVE_CONFIG_H
#  include <config.h>
#endif

#include <stdio.h>
#include <errno.h>

#include "libguile/_scm.h"
#include "libguile/eval.h"
#include "libguile/objects.h"
#include "libguile/smob.h"
#include "libguile/chars.h"

#include "libguile/keywords.h"
#include "libguile/root.h"
#include "libguile/strings.h"

#include "libguile/validate.h"
#include "libguile/ports.h"

#ifdef HAVE_STRING_H
#include <string.h>
#endif

#ifdef HAVE_MALLOC_H
#include <malloc.h>
#endif

#ifdef HAVE_IO_H
#include <io.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#ifdef __MINGW32__
#include <fcntl.h>
#define ftruncate(fd, size) chsize (fd, size)
#endif

\f
/* The port kind table --- a dynamically resized array of port types.  */


/* scm_ptobs scm_numptob
 * implement a dynamicly resized array of ptob records.
 * Indexes into this table are used when generating type
 * tags for smobjects (if you know a tag you can get an index and conversely).
 */
scm_t_ptob_descriptor *scm_ptobs;
long scm_numptob;

/* GC marker for a port with stream of SCM type.  */
SCM 
scm_markstream (SCM ptr)
{
  int openp;
  openp = SCM_CELL_WORD_0 (ptr) & SCM_OPN;
  if (openp)
    return SCM_PACK (SCM_STREAM (ptr));
  else
    return SCM_BOOL_F;
}

/*
 * We choose to use an interface similar to the smob interface with
 * fill_input and write as standard fields, passed to the port
 * type constructor, and optional fields set by setters.
 */

static void
flush_port_default (SCM port SCM_UNUSED)
{
}

static void
end_input_default (SCM port SCM_UNUSED, int offset SCM_UNUSED)
{
}

static size_t
scm_port_free0 (SCM port)
{
  return 0;
}

scm_t_bits
scm_make_port_type (char *name,
                    int (*fill_input) (SCM port),
                    void (*write) (SCM port, const void *data, size_t size))
{
  char *tmp;
  if (255 <= scm_numptob)
    goto ptoberr;
  SCM_DEFER_INTS;
  SCM_SYSCALL (tmp = (char *) realloc ((char *) scm_ptobs,
                                       (1 + scm_numptob)
                                       * sizeof (scm_t_ptob_descriptor)));
  if (tmp)
    {
      scm_ptobs = (scm_t_ptob_descriptor *) tmp;

      scm_ptobs[scm_numptob].name = name;
      scm_ptobs[scm_numptob].mark = 0;
      scm_ptobs[scm_numptob].free = scm_port_free0;
      scm_ptobs[scm_numptob].print = scm_port_print;
      scm_ptobs[scm_numptob].equalp = 0;
      scm_ptobs[scm_numptob].close = 0;

      scm_ptobs[scm_numptob].write = write;
      scm_ptobs[scm_numptob].flush = flush_port_default;

      scm_ptobs[scm_numptob].end_input = end_input_default;
      scm_ptobs[scm_numptob].fill_input = fill_input;
      scm_ptobs[scm_numptob].input_waiting = 0;

      scm_ptobs[scm_numptob].seek = 0;
      scm_ptobs[scm_numptob].truncate = 0;

      scm_numptob++;
    }
  SCM_ALLOW_INTS;
  if (!tmp)
    {
    ptoberr:
      scm_memory_error ("scm_make_port_type");
    }
  /* Make a class object if Goops is present */
  if (scm_port_class)
    scm_make_port_classes (scm_numptob - 1, SCM_PTOBNAME (scm_numptob - 1));
  return scm_tc7_port + (scm_numptob - 1) * 256;
}

void
scm_set_port_mark (long tc, SCM (*mark) (SCM))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].mark = mark;
}

void
scm_set_port_free (long tc, size_t (*free) (SCM))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].free = free;
}

void
scm_set_port_print (long tc, int (*print) (SCM exp, SCM port,
                                           scm_print_state *pstate))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].print = print;
}

void
scm_set_port_equalp (long tc, SCM (*equalp) (SCM, SCM))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].equalp = equalp;
}

void
scm_set_port_flush (long tc, void (*flush) (SCM port))
{
   scm_ptobs[SCM_TC2PTOBNUM (tc)].flush = flush;
}

void
scm_set_port_end_input (long tc, void (*end_input) (SCM port, int offset))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].end_input = end_input;
}

void
scm_set_port_close (long tc, int (*close) (SCM))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].close = close;
}

void
scm_set_port_seek (long tc, off_t (*seek) (SCM port,
                                           off_t OFFSET,
                                           int WHENCE))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].seek = seek;
}

void
scm_set_port_truncate (long tc, void (*truncate) (SCM port, off_t length))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].truncate = truncate;
}

void
scm_set_port_input_waiting (long tc, int (*input_waiting) (SCM))
{
  scm_ptobs[SCM_TC2PTOBNUM (tc)].input_waiting = input_waiting;
}

\f

SCM_DEFINE (scm_char_ready_p, "char-ready?", 0, 1, 0, 
            (SCM port),
            "Return @code{#t} if a character is ready on input @var{port}\n"
            "and return @code{#f} otherwise.  If @code{char-ready?} returns\n"
            "@code{#t} then the next @code{read-char} operation on\n"
            "@var{port} is guaranteed not to hang.  If @var{port} is a file\n"
            "port at end of file then @code{char-ready?} returns @code{#t}.\n"
            "@footnote{@code{char-ready?} exists to make it possible for a\n"
            "program to accept characters from interactive ports without\n"
            "getting stuck waiting for input.  Any input editors associated\n"
            "with such ports must make sure that characters whose existence\n"
            "has been asserted by @code{char-ready?} cannot be rubbed out.\n"
            "If @code{char-ready?} were to return @code{#f} at end of file,\n"
            "a port at end of file would be indistinguishable from an\n"
            "interactive port that has no ready characters.}")
#define FUNC_NAME s_scm_char_ready_p
{
  scm_t_port *pt;

  if (SCM_UNBNDP (port))
    port = scm_cur_inp;
  else
    SCM_VALIDATE_OPINPORT (1, port);

  pt = SCM_PTAB_ENTRY (port);

  /* if the current read buffer is filled, or the
     last pushed-back char has been read and the saved buffer is
     filled, result is true.  */
  if (pt->read_pos < pt->read_end 
      || (pt->read_buf == pt->putback_buf
          && pt->saved_read_pos < pt->saved_read_end))
    return SCM_BOOL_T;
  else
    {
      scm_t_ptob_descriptor *ptob = &scm_ptobs[SCM_PTOBNUM (port)];
      
      if (ptob->input_waiting)
        return SCM_BOOL(ptob->input_waiting (port));
      else
        return SCM_BOOL_T;
    }
}
#undef FUNC_NAME

/* move up to read_len chars from port's putback and/or read buffers
   into memory starting at dest.  returns the number of chars moved.  */
size_t scm_take_from_input_buffers (SCM port, char *dest, size_t read_len)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  size_t chars_read = 0;
  size_t from_buf = min (pt->read_end - pt->read_pos, read_len);

  if (from_buf > 0)
    {
      memcpy (dest, pt->read_pos, from_buf);
      pt->read_pos += from_buf;
      chars_read += from_buf;
      read_len -= from_buf;
      dest += from_buf;
    }

  /* if putback was active, try the real input buffer too.  */
  if (pt->read_buf == pt->putback_buf)
    {
      from_buf = min (pt->saved_read_end - pt->saved_read_pos, read_len);
      if (from_buf > 0)
        {
          memcpy (dest, pt->saved_read_pos, from_buf);
          pt->saved_read_pos += from_buf;
          chars_read += from_buf;
        }
    }
  return chars_read;
}

/* Clear a port's read buffers, returning the contents.  */
SCM_DEFINE (scm_drain_input, "drain-input", 1, 0, 0, 
            (SCM port),
            "This procedure clears a port's input buffers, similar\n"
            "to the way that force-output clears the output buffer.  The\n"
            "contents of the buffers are returned as a single string, e.g.,\n"
            "\n"
            "@lisp\n"
            "(define p (open-input-file ...))\n"
            "(drain-input p) => empty string, nothing buffered yet.\n"
            "(unread-char (read-char p) p)\n"
            "(drain-input p) => initial chars from p, up to the buffer size.\n"
            "@end lisp\n\n"
            "Draining the buffers may be useful for cleanly finishing\n"
            "buffered I/O so that the file descriptor can be used directly\n"
            "for further input.")
#define FUNC_NAME s_scm_drain_input
{
  SCM result;
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  long count;

  SCM_VALIDATE_OPINPORT (1, port);

  count = pt->read_end - pt->read_pos;
  if (pt->read_buf == pt->putback_buf)
    count += pt->saved_read_end - pt->saved_read_pos;

  result = scm_allocate_string (count);
  scm_take_from_input_buffers (port, SCM_STRING_CHARS (result), count);

  return result;
}
#undef FUNC_NAME

\f
/* Standard ports --- current input, output, error, and more(!).  */

SCM_DEFINE (scm_current_input_port, "current-input-port", 0, 0, 0,
            (),
            "Return the current input port.  This is the default port used\n"
            "by many input procedures.  Initially, @code{current-input-port}\n"
            "returns the @dfn{standard input} in Unix and C terminology.")
#define FUNC_NAME s_scm_current_input_port
{
  return scm_cur_inp;
}
#undef FUNC_NAME

SCM_DEFINE (scm_current_output_port, "current-output-port", 0, 0, 0,
            (),
            "Return the current output port.  This is the default port used\n"
            "by many output procedures.  Initially,\n"
            "@code{current-output-port} returns the @dfn{standard output} in\n"
            "Unix and C terminology.")
#define FUNC_NAME s_scm_current_output_port
{
  return scm_cur_outp;
}
#undef FUNC_NAME

SCM_DEFINE (scm_current_error_port, "current-error-port", 0, 0, 0,
           (),
            "Return the port to which errors and warnings should be sent (the\n"
            "@dfn{standard error} in Unix and C terminology).")
#define FUNC_NAME s_scm_current_error_port
{
  return scm_cur_errp;
}
#undef FUNC_NAME

SCM_DEFINE (scm_current_load_port, "current-load-port", 0, 0, 0,
            (),
            "Return the current-load-port.\n"
            "The load port is used internally by @code{primitive-load}.")
#define FUNC_NAME s_scm_current_load_port
{
  return scm_cur_loadp;
}
#undef FUNC_NAME

SCM_DEFINE (scm_set_current_input_port, "set-current-input-port", 1, 0, 0,
           (SCM port),
            "@deffnx {Scheme Procedure} set-current-output-port port\n"
            "@deffnx {Scheme Procedure} set-current-error-port port\n"
            "Change the ports returned by @code{current-input-port},\n"
            "@code{current-output-port} and @code{current-error-port}, respectively,\n"
            "so that they use the supplied @var{port} for input or output.")
#define FUNC_NAME s_scm_set_current_input_port
{
  SCM oinp = scm_cur_inp;
  SCM_VALIDATE_OPINPORT (1, port);
  scm_cur_inp = port;
  return oinp;
}
#undef FUNC_NAME


SCM_DEFINE (scm_set_current_output_port, "set-current-output-port", 1, 0, 0,
            (SCM port),
            "Set the current default output port to @var{port}.")
#define FUNC_NAME s_scm_set_current_output_port
{
  SCM ooutp = scm_cur_outp;
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPOUTPORT (1, port);
  scm_cur_outp = port;
  return ooutp;
}
#undef FUNC_NAME


SCM_DEFINE (scm_set_current_error_port, "set-current-error-port", 1, 0, 0,
            (SCM port),
            "Set the current default error port to @var{port}.")
#define FUNC_NAME s_scm_set_current_error_port
{
  SCM oerrp = scm_cur_errp;
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPOUTPORT (1, port);
  scm_cur_errp = port;
  return oerrp;
}
#undef FUNC_NAME

\f
/* The port table --- an array of pointers to ports.  */

scm_t_port **scm_i_port_table;

long scm_i_port_table_size = 0; /* Number of ports in scm_i_port_table.  */
long scm_i_port_table_room = 20;        /* Size of the array.  */


SCM
scm_new_port_table_entry (scm_t_bits tag)
#define FUNC_NAME "scm_new_port_table_entry"
{
  /*
    We initialize the cell to empty, this is in case scm_gc_calloc
    triggers GC ; we don't want the GC to scan a half-finished Z.
   */
  
  SCM z = scm_cons (SCM_EOL, SCM_EOL);
  scm_t_port *entry = (scm_t_port *) scm_gc_calloc (sizeof (scm_t_port), "port");
  if (scm_i_port_table_size == scm_i_port_table_room)
    {
      /* initial malloc is in gc.c.  this doesn't use scm_gc_malloc etc.,
         since it can never be freed during gc.  */
      void *newt = scm_realloc ((char *) scm_i_port_table,
                                (size_t) (sizeof (scm_t_port *)
                                          * scm_i_port_table_room * 2));
      scm_i_port_table = (scm_t_port **) newt;
      scm_i_port_table_room *= 2;
    }

  entry->entry = scm_i_port_table_size;

  entry->file_name = SCM_BOOL_F;
  entry->rw_active = SCM_PORT_NEITHER;

  scm_i_port_table[scm_i_port_table_size] = entry;
  scm_i_port_table_size++;

  entry->port = z;
  SCM_SET_CELL_TYPE(z, tag);
  SCM_SETPTAB_ENTRY(z, entry);
  
  return z;
}
#undef FUNC_NAME

#if SCM_ENABLE_DEPRECATED==1
SCM_API scm_t_port *
scm_add_to_port_table (SCM port)
{
  SCM z = scm_new_port_table_entry (scm_tc7_port);
  scm_t_port * pt = SCM_PTAB_ENTRY(z);

  pt->port = port;
  SCM_SETCAR(z, SCM_EOL);
  SCM_SETCDR(z, SCM_EOL);
  SCM_SETPTAB_ENTRY (port, pt);
  return pt;
}
#endif


/* Remove a port from the table and destroy it.  */
void
scm_remove_from_port_table (SCM port)
#define FUNC_NAME "scm_remove_from_port_table"
{
  scm_t_port *p = SCM_PTAB_ENTRY (port);
  long i = p->entry;

  if (i >= scm_i_port_table_size)
    SCM_MISC_ERROR ("Port not in table: ~S", scm_list_1 (port));
  if (p->putback_buf)
    scm_gc_free (p->putback_buf, p->putback_buf_size, "putback buffer");
  scm_gc_free (p, sizeof (scm_t_port), "port");
  /* Since we have just freed slot i we can shrink the table by moving
     the last entry to that slot... */
  if (i < scm_i_port_table_size - 1)
    {
      scm_i_port_table[i] = scm_i_port_table[scm_i_port_table_size - 1];
      scm_i_port_table[i]->entry = i;
    }
  SCM_SETPTAB_ENTRY (port, 0);
  scm_i_port_table_size--;
}
#undef FUNC_NAME


#ifdef GUILE_DEBUG
/* Functions for debugging.  */

SCM_DEFINE (scm_pt_size, "pt-size", 0, 0, 0,
            (),
            "Return the number of ports in the port table.  @code{pt-size}\n"
            "is only included in @code{--enable-guile-debug} builds.")
#define FUNC_NAME s_scm_pt_size
{
  return SCM_MAKINUM (scm_i_port_table_size);
}
#undef FUNC_NAME

SCM_DEFINE (scm_pt_member, "pt-member", 1, 0, 0,
            (SCM index),
            "Return the port at @var{index} in the port table.\n"
            "@code{pt-member} is only included in\n"
            "@code{--enable-guile-debug} builds.")
#define FUNC_NAME s_scm_pt_member
{
  long i;
  SCM_VALIDATE_INUM_COPY (1, index, i);
  if (i < 0 || i >= scm_i_port_table_size)
    return SCM_BOOL_F;
  else
    return scm_i_port_table[i]->port;
}
#undef FUNC_NAME
#endif

void
scm_port_non_buffer (scm_t_port *pt)
{
  pt->read_pos = pt->read_buf = pt->read_end = &pt->shortbuf;
  pt->write_buf = pt->write_pos = &pt->shortbuf;
  pt->read_buf_size = pt->write_buf_size = 1;
  pt->write_end = pt->write_buf + pt->write_buf_size;
}

\f
/* Revealed counts --- an oddity inherited from SCSH.  */

/* Find a port in the table and return its revealed count.
   Also used by the garbage collector.
 */

int
scm_revealed_count (SCM port)
{
  return SCM_REVEALED(port);
}



/* Return the revealed count for a port.  */

SCM_DEFINE (scm_port_revealed, "port-revealed", 1, 0, 0,
           (SCM port),
            "Return the revealed count for @var{port}.")
#define FUNC_NAME s_scm_port_revealed
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  return SCM_MAKINUM (scm_revealed_count (port));
}
#undef FUNC_NAME

/* Set the revealed count for a port.  */
SCM_DEFINE (scm_set_port_revealed_x, "set-port-revealed!", 2, 0, 0,
           (SCM port, SCM rcount),
            "Sets the revealed count for a port to a given value.\n"
            "The return value is unspecified.")
#define FUNC_NAME s_scm_set_port_revealed_x
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  SCM_VALIDATE_INUM (2, rcount);
  SCM_REVEALED (port) = SCM_INUM (rcount);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME


\f
/* Retrieving a port's mode.  */

/* Return the flags that characterize a port based on the mode
 * string used to open a file for that port.
 *
 * See PORT FLAGS in scm.h
 */

long
scm_mode_bits (char *modes)
{
  return (SCM_OPN
          | (strchr (modes, 'r') || strchr (modes, '+') ? SCM_RDNG : 0)
          | (   strchr (modes, 'w')
             || strchr (modes, 'a')
             || strchr (modes, '+') ? SCM_WRTNG : 0)
          | (strchr (modes, '0') ? SCM_BUF0 : 0)
          | (strchr (modes, 'l') ? SCM_BUFLINE : 0));
}


/* Return the mode flags from an open port.
 * Some modes such as "append" are only used when opening
 * a file and are not returned here.  */

SCM_DEFINE (scm_port_mode, "port-mode", 1, 0, 0,
           (SCM port),
            "Return the port modes associated with the open port @var{port}.\n"
            "These will not necessarily be identical to the modes used when\n"
            "the port was opened, since modes such as \"append\" which are\n"
            "used only during port creation are not retained.")
#define FUNC_NAME s_scm_port_mode
{
  char modes[4];
  modes[0] = '\0';

  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPPORT (1, port);
  if (SCM_CELL_WORD_0 (port) & SCM_RDNG) {
    if (SCM_CELL_WORD_0 (port) & SCM_WRTNG)
      strcpy (modes, "r+");
    else
      strcpy (modes, "r");
  }
  else if (SCM_CELL_WORD_0 (port) & SCM_WRTNG)
    strcpy (modes, "w");
  if (SCM_CELL_WORD_0 (port) & SCM_BUF0)
    strcat (modes, "0");
  return scm_mem2string (modes, strlen (modes));
}
#undef FUNC_NAME


\f
/* Closing ports.  */

/* scm_close_port
 * Call the close operation on a port object. 
 * see also scm_close.
 */
SCM_DEFINE (scm_close_port, "close-port", 1, 0, 0,
           (SCM port),
            "Close the specified port object.  Return @code{#t} if it\n"
            "successfully closes a port or @code{#f} if it was already\n"
            "closed.  An exception may be raised if an error occurs, for\n"
            "example when flushing buffered output.  See also @ref{Ports and\n"
            "File Descriptors, close}, for a procedure which can close file\n"
            "descriptors.")
#define FUNC_NAME s_scm_close_port
{
  size_t i;
  int rv;

  port = SCM_COERCE_OUTPORT (port);

  SCM_VALIDATE_PORT (1, port);
  if (SCM_CLOSEDP (port))
    return SCM_BOOL_F;
  i = SCM_PTOBNUM (port);
  if (scm_ptobs[i].close)
    rv = (scm_ptobs[i].close) (port);
  else
    rv = 0;
  scm_remove_from_port_table (port);
  SCM_CLR_PORT_OPEN_FLAG (port);
  return SCM_BOOL (rv >= 0);
}
#undef FUNC_NAME

SCM_DEFINE (scm_close_input_port, "close-input-port", 1, 0, 0,
           (SCM port),
            "Close the specified input port object.  The routine has no effect if\n"
            "the file has already been closed.  An exception may be raised if an\n"
            "error occurs.  The value returned is unspecified.\n\n"
            "See also @ref{Ports and File Descriptors, close}, for a procedure\n"
            "which can close file descriptors.")
#define FUNC_NAME s_scm_close_input_port
{
  SCM_VALIDATE_INPUT_PORT (1, port);
  scm_close_port (port);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_close_output_port, "close-output-port", 1, 0, 0,
           (SCM port),
            "Close the specified output port object.  The routine has no effect if\n"
            "the file has already been closed.  An exception may be raised if an\n"
            "error occurs.  The value returned is unspecified.\n\n"
            "See also @ref{Ports and File Descriptors, close}, for a procedure\n"
            "which can close file descriptors.")
#define FUNC_NAME s_scm_close_output_port
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OUTPUT_PORT (1, port);
  scm_close_port (port);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_port_for_each, "port-for-each", 1, 0, 0,
            (SCM proc),
            "Apply @var{proc} to each port in the Guile port table\n"
            "in turn.  The return value is unspecified.  More specifically,\n"
            "@var{proc} is applied exactly once to every port that exists\n"
            "in the system at the time @var{port-for-each} is invoked.\n"
            "Changes to the port table while @var{port-for-each} is running\n"
            "have no effect as far as @var{port-for-each} is concerned.") 
#define FUNC_NAME s_scm_port_for_each
{
  long i;
  SCM ports;

  SCM_VALIDATE_PROC (1, proc);

  /* when pre-emptive multithreading is supported, access to the port
     table will need to be controlled by a mutex.  */

  /* Even without pre-emptive multithreading, running arbitrary code
     while scanning the port table is unsafe because the port table
     can change arbitrarily (from a GC, for example).  So we build a
     list in advance while blocking the GC. -mvo */

  SCM_DEFER_INTS;
  scm_block_gc++;
  ports = SCM_EOL;
  for (i = 0; i < scm_i_port_table_size; i++)
    ports = scm_cons (scm_i_port_table[i]->port, ports);
  scm_block_gc--;
  SCM_ALLOW_INTS;

  while (ports != SCM_EOL)
    {
      scm_call_1 (proc, SCM_CAR (ports));
      ports = SCM_CDR (ports);
    }

  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

\f
/* Utter miscellany.  Gosh, we should clean this up some time.  */

SCM_DEFINE (scm_input_port_p, "input-port?", 1, 0, 0,
           (SCM x),
            "Return @code{#t} if @var{x} is an input port, otherwise return\n"
            "@code{#f}.  Any object satisfying this predicate also satisfies\n"
            "@code{port?}.")
#define FUNC_NAME s_scm_input_port_p
{
  return SCM_BOOL (SCM_INPUT_PORT_P (x));
}
#undef FUNC_NAME

SCM_DEFINE (scm_output_port_p, "output-port?", 1, 0, 0,
           (SCM x),
            "Return @code{#t} if @var{x} is an output port, otherwise return\n"
            "@code{#f}.  Any object satisfying this predicate also satisfies\n"
            "@code{port?}.")
#define FUNC_NAME s_scm_output_port_p
{
  x = SCM_COERCE_OUTPORT (x);
  return SCM_BOOL (SCM_OUTPUT_PORT_P (x));
}
#undef FUNC_NAME

SCM_DEFINE (scm_port_p, "port?", 1, 0, 0,
            (SCM x),
            "Return a boolean indicating whether @var{x} is a port.\n"
            "Equivalent to @code{(or (input-port? @var{x}) (output-port?\n"
            "@var{x}))}.")
#define FUNC_NAME s_scm_port_p
{
  return SCM_BOOL (SCM_PORTP (x));
}
#undef FUNC_NAME

SCM_DEFINE (scm_port_closed_p, "port-closed?", 1, 0, 0,
           (SCM port),
            "Return @code{#t} if @var{port} is closed or @code{#f} if it is\n"
            "open.")
#define FUNC_NAME s_scm_port_closed_p
{
  SCM_VALIDATE_PORT (1, port);
  return SCM_BOOL (!SCM_OPPORTP (port));
}
#undef FUNC_NAME

SCM_DEFINE (scm_eof_object_p, "eof-object?", 1, 0, 0,
           (SCM x),
            "Return @code{#t} if @var{x} is an end-of-file object; otherwise\n"
            "return @code{#f}.")
#define FUNC_NAME s_scm_eof_object_p
{
  return SCM_BOOL(SCM_EOF_OBJECT_P (x));
}
#undef FUNC_NAME

SCM_DEFINE (scm_force_output, "force-output", 0, 1, 0,
           (SCM port),
            "Flush the specified output port, or the current output port if @var{port}\n"
            "is omitted.  The current output buffer contents are passed to the\n"
            "underlying port implementation (e.g., in the case of fports, the\n"
            "data will be written to the file and the output buffer will be cleared.)\n"
            "It has no effect on an unbuffered port.\n\n"
            "The return value is unspecified.")
#define FUNC_NAME s_scm_force_output
{
  if (SCM_UNBNDP (port))
    port = scm_cur_outp;
  else
    {
      port = SCM_COERCE_OUTPORT (port);
      SCM_VALIDATE_OPOUTPORT (1, port);
    }
  scm_flush (port);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_flush_all_ports, "flush-all-ports", 0, 0, 0,
            (),
            "Equivalent to calling @code{force-output} on\n"
            "all open output ports.  The return value is unspecified.")
#define FUNC_NAME s_scm_flush_all_ports
{
  size_t i;

  for (i = 0; i < scm_i_port_table_size; i++)
    {
      if (SCM_OPOUTPORTP (scm_i_port_table[i]->port))
        scm_flush (scm_i_port_table[i]->port);
    }
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_read_char, "read-char", 0, 1, 0,
           (SCM port),
            "Return the next character available from @var{port}, updating\n"
            "@var{port} to point to the following character.  If no more\n"
            "characters are available, the end-of-file object is returned.")
#define FUNC_NAME s_scm_read_char
{
  int c;
  if (SCM_UNBNDP (port))
    port = scm_cur_inp;
  SCM_VALIDATE_OPINPORT (1, port);
  c = scm_getc (port);
  if (EOF == c)
    return SCM_EOF_VAL;
  return SCM_MAKE_CHAR (c);
}
#undef FUNC_NAME

/* this should only be called when the read buffer is empty.  it
   tries to refill the read buffer.  it returns the first char from
   the port, which is either EOF or *(pt->read_pos).  */
int
scm_fill_input (SCM port)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);

  if (pt->read_buf == pt->putback_buf)
    {
      /* finished reading put-back chars.  */
      pt->read_buf = pt->saved_read_buf;
      pt->read_pos = pt->saved_read_pos;
      pt->read_end = pt->saved_read_end;
      pt->read_buf_size = pt->saved_read_buf_size;
      if (pt->read_pos < pt->read_end)
        return *(pt->read_pos);
    }
  return scm_ptobs[SCM_PTOBNUM (port)].fill_input (port);
}

int 
scm_getc (SCM port)
{
  int c;
  scm_t_port *pt = SCM_PTAB_ENTRY (port);

  if (pt->rw_active == SCM_PORT_WRITE)
    /* may be marginally faster than calling scm_flush.  */
    scm_ptobs[SCM_PTOBNUM (port)].flush (port);
  
  if (pt->rw_random)
    pt->rw_active = SCM_PORT_READ;

  if (pt->read_pos >= pt->read_end)
    {
      if (scm_fill_input (port) == EOF)
        return EOF;
    }

  c = *(pt->read_pos++);

  switch (c)
    {
      case '\n':
        SCM_INCLINE (port);
        break;
      case '\t':
        SCM_TABCOL (port);
        break;
      default:
        SCM_INCCOL (port);
        break;
    }
 
  return c;
}

void 
scm_putc (char c, SCM port)
{
  scm_lfwrite (&c, 1, port);
}

void 
scm_puts (const char *s, SCM port)
{
  scm_lfwrite (s, strlen (s), port);
}

/* scm_lfwrite
 *
 * This function differs from scm_c_write; it updates port line and
 * column. */

void 
scm_lfwrite (const char *ptr, size_t size, SCM port)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  scm_t_ptob_descriptor *ptob = &scm_ptobs[SCM_PTOBNUM (port)];

  if (pt->rw_active == SCM_PORT_READ)
    scm_end_input (port);

  ptob->write (port, ptr, size);

  for (; size; ptr++, size--) {
    if (*ptr == '\n') {
      SCM_INCLINE(port);
    }
    else if (*ptr == '\t') {
      SCM_TABCOL(port);
    }
    else {
      SCM_INCCOL(port);
    }
  }

  if (pt->rw_random)
    pt->rw_active = SCM_PORT_WRITE;
}

/* scm_c_read
 *
 * Used by an application to read arbitrary number of bytes from an
 * SCM port.  Same semantics as libc read, except that scm_c_read only
 * returns less than SIZE bytes if at end-of-file.
 *
 * Warning: Doesn't update port line and column counts!  */

size_t
scm_c_read (SCM port, void *buffer, size_t size)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  size_t n_read = 0, n_available;

  if (pt->rw_active == SCM_PORT_WRITE)
    scm_ptobs[SCM_PTOBNUM (port)].flush (port);

  if (pt->rw_random)
    pt->rw_active = SCM_PORT_READ;

  if (SCM_READ_BUFFER_EMPTY_P (pt))
    {
      if (scm_fill_input (port) == EOF)
        return 0;
    }
  
  n_available = pt->read_end - pt->read_pos;
  
  while (n_available < size)
    {
      memcpy (buffer, pt->read_pos, n_available);
      buffer = (char *) buffer + n_available;
      pt->read_pos += n_available;
      n_read += n_available;
      
      if (SCM_READ_BUFFER_EMPTY_P (pt))
        {
          if (scm_fill_input (port) == EOF)
            return n_read;
        }

      size -= n_available;
      n_available = pt->read_end - pt->read_pos;
    }

  memcpy (buffer, pt->read_pos, size);
  pt->read_pos += size;

  return n_read + size;
}

/* scm_c_write
 *
 * Used by an application to write arbitrary number of bytes to an SCM
 * port.  Similar semantics as libc write.  However, unlike libc
 * write, scm_c_write writes the requested number of bytes and has no
 * return value.
 *
 * Warning: Doesn't update port line and column counts!
 */

void 
scm_c_write (SCM port, const void *ptr, size_t size)
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);
  scm_t_ptob_descriptor *ptob = &scm_ptobs[SCM_PTOBNUM (port)];

  if (pt->rw_active == SCM_PORT_READ)
    scm_end_input (port);

  ptob->write (port, ptr, size);

  if (pt->rw_random)
    pt->rw_active = SCM_PORT_WRITE;
}

void 
scm_flush (SCM port)
{
  long i = SCM_PTOBNUM (port);
  (scm_ptobs[i].flush) (port);
}

void
scm_end_input (SCM port)
{
  long offset;
  scm_t_port *pt = SCM_PTAB_ENTRY (port);

  if (pt->read_buf == pt->putback_buf)
    {
      offset = pt->read_end - pt->read_pos;
      pt->read_buf = pt->saved_read_buf;
      pt->read_pos = pt->saved_read_pos;
      pt->read_end = pt->saved_read_end;
      pt->read_buf_size = pt->saved_read_buf_size;
    }
  else
    offset = 0;

  scm_ptobs[SCM_PTOBNUM (port)].end_input (port, offset);
}

\f


void 
scm_ungetc (int c, SCM port)
#define FUNC_NAME "scm_ungetc"
{
  scm_t_port *pt = SCM_PTAB_ENTRY (port);

  if (pt->read_buf == pt->putback_buf)
    /* already using the put-back buffer.  */
    {
      /* enlarge putback_buf if necessary.  */
      if (pt->read_end == pt->read_buf + pt->read_buf_size
          && pt->read_buf == pt->read_pos)
        {
          size_t new_size = pt->read_buf_size * 2;
          unsigned char *tmp = (unsigned char *)
            scm_gc_realloc (pt->putback_buf, pt->read_buf_size, new_size,
                            "putback buffer");

          pt->read_pos = pt->read_buf = pt->putback_buf = tmp;
          pt->read_end = pt->read_buf + pt->read_buf_size;
          pt->read_buf_size = pt->putback_buf_size = new_size;
        }

      /* shift any existing bytes to buffer + 1.  */
      if (pt->read_pos == pt->read_end)
        pt->read_end = pt->read_buf + 1;
      else if (pt->read_pos != pt->read_buf + 1)
        {
          int count = pt->read_end - pt->read_pos;

          memmove (pt->read_buf + 1, pt->read_pos, count);
          pt->read_end = pt->read_buf + 1 + count;
        }

      pt->read_pos = pt->read_buf;
    }
  else
    /* switch to the put-back buffer.  */
    {
      if (pt->putback_buf == NULL)
        {
          pt->putback_buf
            = (unsigned char *) scm_gc_malloc (SCM_INITIAL_PUTBACK_BUF_SIZE,
                                               "putback buffer");
          pt->putback_buf_size = SCM_INITIAL_PUTBACK_BUF_SIZE;
        }

      pt->saved_read_buf = pt->read_buf;
      pt->saved_read_pos = pt->read_pos;
      pt->saved_read_end = pt->read_end;
      pt->saved_read_buf_size = pt->read_buf_size;

      pt->read_pos = pt->read_buf = pt->putback_buf;
      pt->read_end = pt->read_buf + 1;
      pt->read_buf_size = pt->putback_buf_size;
    }

  *pt->read_buf = c;

  if (pt->rw_random)
    pt->rw_active = SCM_PORT_READ;

  if (c == '\n')
    {
      /* What should col be in this case?
       * We'll leave it at -1.
       */
      SCM_LINUM (port) -= 1;
    }
  else
    SCM_COL(port) -= 1;
}
#undef FUNC_NAME


void 
scm_ungets (const char *s, int n, SCM port)
{
  /* This is simple minded and inefficient, but unreading strings is
   * probably not a common operation, and remember that line and
   * column numbers have to be handled...
   *
   * Please feel free to write an optimized version!
   */
  while (n--)
    scm_ungetc (s[n], port);
}


SCM_DEFINE (scm_peek_char, "peek-char", 0, 1, 0,
           (SCM port),
            "Return the next character available from @var{port},\n"
            "@emph{without} updating @var{port} to point to the following\n"
            "character.  If no more characters are available, the\n"
            "end-of-file object is returned.@footnote{The value returned by\n"
            "a call to @code{peek-char} is the same as the value that would\n"
            "have been returned by a call to @code{read-char} on the same\n"
            "port.  The only difference is that the very next call to\n"
            "@code{read-char} or @code{peek-char} on that @var{port} will\n"
            "return the value returned by the preceding call to\n"
            "@code{peek-char}.  In particular, a call to @code{peek-char} on\n"
            "an interactive port will hang waiting for input whenever a call\n"
            "to @code{read-char} would have hung.}")
#define FUNC_NAME s_scm_peek_char
{
  int c;
  if (SCM_UNBNDP (port))
    port = scm_cur_inp;
  else
    SCM_VALIDATE_OPINPORT (1, port);
  c = scm_getc (port);
  if (EOF == c)
    return SCM_EOF_VAL;
  scm_ungetc (c, port);
  return SCM_MAKE_CHAR (c);
}
#undef FUNC_NAME

SCM_DEFINE (scm_unread_char, "unread-char", 1, 1, 0,
            (SCM cobj, SCM port),
            "Place @var{char} in @var{port} so that it will be read by the\n"
            "next read operation.  If called multiple times, the unread characters\n"
            "will be read again in last-in first-out order.  If @var{port} is\n"
            "not supplied, the current input port is used.")
#define FUNC_NAME s_scm_unread_char
{
  int c;

  SCM_VALIDATE_CHAR (1, cobj);
  if (SCM_UNBNDP (port))
    port = scm_cur_inp;
  else
    SCM_VALIDATE_OPINPORT (2, port);

  c = SCM_CHAR (cobj);

  scm_ungetc (c, port);
  return cobj;
}
#undef FUNC_NAME

SCM_DEFINE (scm_unread_string, "unread-string", 2, 0, 0,
            (SCM str, SCM port),
            "Place the string @var{str} in @var{port} so that its characters will be\n"
            "read in subsequent read operations.  If called multiple times, the\n"
            "unread characters will be read again in last-in first-out order.  If\n"
            "@var{port} is not supplied, the current-input-port is used.")
#define FUNC_NAME s_scm_unread_string
{
  SCM_VALIDATE_STRING (1, str);
  if (SCM_UNBNDP (port))
    port = scm_cur_inp;
  else
    SCM_VALIDATE_OPINPORT (2, port);

  scm_ungets (SCM_STRING_CHARS (str), SCM_STRING_LENGTH (str), port);
  
  return str;
}
#undef FUNC_NAME

SCM_DEFINE (scm_seek, "seek", 3, 0, 0,
            (SCM fd_port, SCM offset, SCM whence),
            "Sets the current position of @var{fd/port} to the integer\n"
            "@var{offset}, which is interpreted according to the value of\n"
            "@var{whence}.\n"
            "\n"
            "One of the following variables should be supplied for\n"
            "@var{whence}:\n"
            "@defvar SEEK_SET\n"
            "Seek from the beginning of the file.\n"
            "@end defvar\n"
            "@defvar SEEK_CUR\n"
            "Seek from the current position.\n"
            "@end defvar\n"
            "@defvar SEEK_END\n"
            "Seek from the end of the file.\n"
            "@end defvar\n"
            "If @var{fd/port} is a file descriptor, the underlying system\n"
            "call is @code{lseek}.  @var{port} may be a string port.\n"
            "\n"
            "The value returned is the new position in the file.  This means\n"
            "that the current position of a port can be obtained using:\n"
            "@lisp\n"
            "(seek port 0 SEEK_CUR)\n"
            "@end lisp")
#define FUNC_NAME s_scm_seek
{
  off_t off;
  off_t rv;
  int how;

  fd_port = SCM_COERCE_OUTPORT (fd_port);

  off = SCM_NUM2LONG (2, offset);
  SCM_VALIDATE_INUM_COPY (3, whence, how);
  if (how != SEEK_SET && how != SEEK_CUR && how != SEEK_END)
    SCM_OUT_OF_RANGE (3, whence);
  if (SCM_OPPORTP (fd_port))
    {
      scm_t_ptob_descriptor *ptob = scm_ptobs + SCM_PTOBNUM (fd_port);

      if (!ptob->seek)
        SCM_MISC_ERROR ("port is not seekable", 
                        scm_cons (fd_port, SCM_EOL));
      else
        rv = ptob->seek (fd_port, off, how);
    }
  else /* file descriptor?.  */
    {
      SCM_VALIDATE_INUM (1, fd_port);
      rv = lseek (SCM_INUM (fd_port), off, how);
      if (rv == -1)
        SCM_SYSERROR;
    }
  return scm_long2num (rv);
}
#undef FUNC_NAME

#ifdef __MINGW32__
/* Define this function since it is not supported under Windows. */
static int truncate (char *file, int length)
{
  int ret = -1, fdes;
  if ((fdes = open (file, O_BINARY | O_WRONLY)) != -1)
    {
      ret = chsize (fdes, length);
      close (fdes);
    }
  return ret;
}
#endif /* __MINGW32__ */

SCM_DEFINE (scm_truncate_file, "truncate-file", 1, 1, 0,
            (SCM object, SCM length),
            "Truncates the object referred to by @var{object} to at most\n"
            "@var{length} bytes.  @var{object} can be a string containing a\n"
            "file name or an integer file descriptor or a port.\n"
            "@var{length} may be omitted if @var{object} is not a file name,\n"
            "in which case the truncation occurs at the current port.\n"
            "position.  The return value is unspecified.")
#define FUNC_NAME s_scm_truncate_file
{
  int rv;
  off_t c_length;

  /* object can be a port, fdes or filename.  */

  if (SCM_UNBNDP (length))
    {
      /* must supply length if object is a filename.  */
      if (SCM_STRINGP (object))
        SCM_MISC_ERROR("must supply length if OBJECT is a filename", SCM_EOL);
      
      length = scm_seek (object, SCM_INUM0, SCM_MAKINUM (SEEK_CUR));
    }
  c_length = SCM_NUM2LONG (2, length);
  if (c_length < 0)
    SCM_MISC_ERROR ("negative offset", SCM_EOL);

  object = SCM_COERCE_OUTPORT (object);
  if (SCM_INUMP (object))
    {
      SCM_SYSCALL (rv = ftruncate (SCM_INUM (object), c_length));
    }
  else if (SCM_OPOUTPORTP (object))
    {
      scm_t_port *pt = SCM_PTAB_ENTRY (object);
      scm_t_ptob_descriptor *ptob = scm_ptobs + SCM_PTOBNUM (object);
      
      if (!ptob->truncate)
        SCM_MISC_ERROR ("port is not truncatable", SCM_EOL);
      if (pt->rw_active == SCM_PORT_READ)
        scm_end_input (object);
      else if (pt->rw_active == SCM_PORT_WRITE)
        ptob->flush (object);
      
      ptob->truncate (object, c_length);
      rv = 0;
    }
  else
    {
      SCM_VALIDATE_STRING (1, object);
      SCM_SYSCALL (rv = truncate (SCM_STRING_CHARS (object), c_length));
    }
  if (rv == -1)
    SCM_SYSERROR;
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_port_line, "port-line", 1, 0, 0,
            (SCM port),
            "Return the current line number for @var{port}.")
#define FUNC_NAME s_scm_port_line
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  return SCM_MAKINUM (SCM_LINUM (port));
}
#undef FUNC_NAME

SCM_DEFINE (scm_set_port_line_x, "set-port-line!", 2, 0, 0,
            (SCM port, SCM line),
            "Set the current line number for @var{port} to @var{line}.")
#define FUNC_NAME s_scm_set_port_line_x
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  SCM_VALIDATE_INUM (2, line);
  SCM_PTAB_ENTRY (port)->line_number = SCM_INUM (line);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_port_column, "port-column", 1, 0, 0,
            (SCM port),
            "@deffnx {Scheme Procedure} port-line port\n"
            "Return the current column number or line number of @var{port},\n"
            "using the current input port if none is specified.  If the number is\n"
            "unknown, the result is #f.  Otherwise, the result is a 0-origin integer\n"
            "- i.e. the first character of the first line is line 0, column 0.\n"
            "(However, when you display a file position, for example in an error\n"
            "message, we recommend you add 1 to get 1-origin integers.  This is\n"
            "because lines and column numbers traditionally start with 1, and that is\n"
            "what non-programmers will find most natural.)")
#define FUNC_NAME s_scm_port_column
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  return SCM_MAKINUM (SCM_COL (port));
}
#undef FUNC_NAME

SCM_DEFINE (scm_set_port_column_x, "set-port-column!", 2, 0, 0,
            (SCM port, SCM column),
            "@deffnx {Scheme Procedure} set-port-line! port line\n"
            "Set the current column or line number of @var{port}, using the\n"
            "current input port if none is specified.")
#define FUNC_NAME s_scm_set_port_column_x
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  SCM_VALIDATE_INUM (2, column);
  SCM_PTAB_ENTRY (port)->column_number = SCM_INUM (column);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

SCM_DEFINE (scm_port_filename, "port-filename", 1, 0, 0,
            (SCM port),
            "Return the filename associated with @var{port}.  This function returns\n"
            "the strings \"standard input\", \"standard output\" and \"standard error\"\n"
            "when called on the current input, output and error ports respectively.")
#define FUNC_NAME s_scm_port_filename
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  return SCM_FILENAME (port);
}
#undef FUNC_NAME

SCM_DEFINE (scm_set_port_filename_x, "set-port-filename!", 2, 0, 0,
            (SCM port, SCM filename),
            "Change the filename associated with @var{port}, using the current input\n"
            "port if none is specified.  Note that this does not change the port's\n"
            "source of data, but only the value that is returned by\n"
            "@code{port-filename} and reported in diagnostic output.")
#define FUNC_NAME s_scm_set_port_filename_x
{
  port = SCM_COERCE_OUTPORT (port);
  SCM_VALIDATE_OPENPORT (1, port);
  /* We allow the user to set the filename to whatever he likes.  */
  SCM_SET_FILENAME (port, filename);
  return SCM_UNSPECIFIED;
}
#undef FUNC_NAME

#ifndef ttyname
extern char * ttyname();
#endif

void
scm_print_port_mode (SCM exp, SCM port)
{
  scm_puts (SCM_CLOSEDP (exp)
            ? "closed: "
            : (SCM_RDNG & SCM_CELL_WORD_0 (exp)
               ? (SCM_WRTNG & SCM_CELL_WORD_0 (exp)
                  ? "input-output: "
                  : "input: ")
               : (SCM_WRTNG & SCM_CELL_WORD_0 (exp)
                  ? "output: "
                  : "bogus: ")),
            port);
}

int
scm_port_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
{
  char *type = SCM_PTOBNAME (SCM_PTOBNUM (exp));
  if (!type)
    type = "port";
  scm_puts ("#<", port);
  scm_print_port_mode (exp, port);
  scm_puts (type, port);
  scm_putc (' ', port);
  scm_intprint (SCM_CELL_WORD_1 (exp), 16, port);
  scm_putc ('>', port);
  return 1;
}

void
scm_ports_prehistory ()
{
  scm_numptob = 0;
  scm_ptobs = (scm_t_ptob_descriptor *) scm_malloc (sizeof (scm_t_ptob_descriptor));
}

\f

/* Void ports.   */

scm_t_bits scm_tc16_void_port = 0;

static int fill_input_void_port (SCM port SCM_UNUSED)
{
  return EOF;
}

static void
write_void_port (SCM port SCM_UNUSED,
                 const void *data SCM_UNUSED,
                 size_t size SCM_UNUSED)
{
}

SCM
scm_void_port (char *mode_str)
{
  SCM_DEFER_INTS;
  {
    int mode_bits = scm_mode_bits (mode_str);
    SCM answer = scm_new_port_table_entry (scm_tc16_void_port);
    scm_t_port * pt = SCM_PTAB_ENTRY(answer);

    scm_port_non_buffer (pt);
  
    SCM_SETSTREAM (answer, 0);
    SCM_SET_CELL_TYPE (answer, scm_tc16_void_port | mode_bits);
    SCM_ALLOW_INTS;
    return answer;
  }
}

SCM_DEFINE (scm_sys_make_void_port, "%make-void-port", 1, 0, 0,
            (SCM mode),
            "Create and return a new void port.  A void port acts like\n"
            "@file{/dev/null}.  The @var{mode} argument\n"
            "specifies the input/output modes for this port: see the\n"
            "documentation for @code{open-file} in @ref{File Ports}.")
#define FUNC_NAME s_scm_sys_make_void_port
{
  SCM_VALIDATE_STRING (1, mode);
  return scm_void_port (SCM_STRING_CHARS (mode));
}
#undef FUNC_NAME

\f
/* Initialization.  */

void
scm_init_ports ()
{
  /* lseek() symbols.  */
  scm_c_define ("SEEK_SET", SCM_MAKINUM (SEEK_SET));
  scm_c_define ("SEEK_CUR", SCM_MAKINUM (SEEK_CUR));
  scm_c_define ("SEEK_END", SCM_MAKINUM (SEEK_END));

  scm_tc16_void_port = scm_make_port_type ("void", fill_input_void_port, 
                                           write_void_port);
#include "libguile/ports.x"
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/