yap-6.3/packages/PLStream/pl-file.c

/*  $Id$

    Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        wielemak@science.uva.nl
    WWW:           http://www.swi-prolog.org
    Copyright (C): 1985-2008, University of Amsterdam

    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
*/

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
This module is far too big.  It defines a layer around open(), etc.   to
get  opening  and  closing  of  files to the symbolic level required for
Prolog.  It also defines basic I/O  predicates,  stream  based  I/O  and
finally  a  bundle  of  operations  on  files,  such  as name expansion,
renaming, deleting, etc.  Most of this module is rather straightforward.

If time is there I will have a look at all this to  clean  it.   Notably
handling times must be cleaned, but that not only holds for this module.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

/*#define O_DEBUG 1*/
/*#define O_DEBUG_MT 1*/

#include "pl-incl.h"
#include "pl-ctype.h"
#include "pl-utf8.h"
#include <errno.h>

#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_BSTRING_H
#include <bstring.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef HAVE_WINSOCK2_H
#include <winsock2.h>
#endif

#define LOCK()   PL_LOCK(L_FILE)	/* MT locking */
#define UNLOCK() PL_UNLOCK(L_FILE)

#undef LD				/* fetch LD once per function */
#define LD LOCAL_LD

static int	bad_encoding(const char *msg, atom_t name);
static int	noprotocol(void);

static int streamStatus(IOSTREAM *s);

const atom_t standardStreams[] =
{ ATOM_user_input,			/* 0 */
  ATOM_user_output,			/* 1 */
  ATOM_user_error,			/* 2 */
  ATOM_current_input,			/* 3 */
  ATOM_current_output,			/* 4 */
  ATOM_protocol,			/* 5 */
  NULL_ATOM
};


static int
standardStreamIndexFromName(atom_t name)
{ const atom_t *ap;

  for(ap=standardStreams; *ap; ap++)
  { if ( *ap == name )
      return (int)(ap - standardStreams);
  }

  return -1;
}


static int
standardStreamIndexFromStream(IOSTREAM *s)
{ GET_LD
  IOSTREAM **sp = LD->IO.streams;
  int i = 0;

  for( ; i<6; i++, sp++ )
  { if ( *sp == s )
      return i;
  }

  return -1;
}


		 /*******************************
		 *	   BOOKKEEPING		*
		 *******************************/

static void aliasStream(IOSTREAM *s, atom_t alias);
static void unaliasStream(IOSTREAM *s, atom_t name);

static Table streamAliases;		/* alias --> stream */
static Table streamContext;		/* stream --> extra data */

typedef struct _alias
{ struct _alias *next;
  atom_t name;
} alias;


#define IO_TELL	0x001			/* opened by tell/1 */
#define IO_SEE  0x002			/* opened by see/1 */

typedef struct
{ alias *alias_head;
  alias *alias_tail;
  atom_t filename;			/* associated filename */
  unsigned flags;
} stream_context;


static stream_context *
getStreamContext(IOSTREAM *s)
{ Symbol symb;

  if ( !(symb = lookupHTable(streamContext, s)) )
  { GET_LD
    stream_context *ctx = allocHeap(sizeof(*ctx));

    DEBUG(1, Sdprintf("Created ctx=%p for stream %p\n", ctx, s));

    ctx->alias_head = ctx->alias_tail = NULL;
    ctx->filename = NULL_ATOM;
    ctx->flags = 0;
    addHTable(streamContext, s, ctx);

    return ctx;
  }

  return symb->value;
}


void
aliasStream(IOSTREAM *s, atom_t name)
{ GET_LD
  stream_context *ctx;
  Symbol symb;
  alias *a;

					/* ensure name is free (error?) */
  if ( (symb = lookupHTable(streamAliases, (void *)name)) )
    unaliasStream(symb->value, name);

  ctx = getStreamContext(s);
  addHTable(streamAliases, (void *)name, s);
  PL_register_atom(name);

  a = allocHeap(sizeof(*a));
  a->next = NULL;
  a->name = name;

  if ( ctx->alias_tail )
  { ctx->alias_tail->next = a;
    ctx->alias_tail = a;
  } else
  { ctx->alias_head = ctx->alias_tail = a;
  }
}

/* MT: Locked by freeStream()
*/

static void
unaliasStream(IOSTREAM *s, atom_t name)
{ GET_LD
  Symbol symb;

  if ( name )
  { if ( (symb = lookupHTable(streamAliases, (void *)name)) )
    { deleteSymbolHTable(streamAliases, symb);

      if ( (symb=lookupHTable(streamContext, s)) )
      { stream_context *ctx = symb->value;
	alias **a;

	for(a = &ctx->alias_head; *a; a = &(*a)->next)
	{ if ( (*a)->name == name )
	  { alias *tmp = *a;

	    *a = tmp->next;
	    freeHeap(tmp, sizeof(*tmp));
	    if ( tmp == ctx->alias_tail )
	      ctx->alias_tail = NULL;

	    break;
	  }
	}
      }

      PL_unregister_atom(name);
    }
  } else				/* delete them all */
  { if ( (symb=lookupHTable(streamContext, s)) )
    { stream_context *ctx = symb->value;
      alias *a, *n;

      for(a = ctx->alias_head; a; a=n)
      { Symbol s2;

	n = a->next;

	if ( (s2 = lookupHTable(streamAliases, (void *)a->name)) )
	{ deleteSymbolHTable(streamAliases, s2);
	  PL_unregister_atom(a->name);
	}

	freeHeap(a, sizeof(*a));
      }

      ctx->alias_head = ctx->alias_tail = NULL;
    }
  }
}


static void
freeStream(IOSTREAM *s)
{ GET_LD
  Symbol symb;
  int i;
  IOSTREAM **sp;

  DEBUG(1, Sdprintf("freeStream(%p)\n", s));

  LOCK();
  unaliasStream(s, NULL_ATOM);
  if ( (symb=lookupHTable(streamContext, s)) )
  { stream_context *ctx = symb->value;

    if ( ctx->filename != NULL_ATOM )
    { PL_unregister_atom(ctx->filename);

      if ( ctx->filename == source_file_name )
      { source_file_name = NULL_ATOM;	/* TBD: pop? */
	source_line_no = -1;
      }
    }

    freeHeap(ctx, sizeof(*ctx));
    deleteSymbolHTable(streamContext, symb);
  }
					/* if we are a standard stream */
					/* reassociate with standard I/O */
					/* NOTE: there may be more! */
  for(i=0, sp = LD->IO.streams; i<6; i++, sp++)
  { if ( *sp == s )
    { if ( s->flags & SIO_INPUT )
	*sp = Sinput;
      else if ( sp == &Suser_error )
	*sp = Serror;
      else if ( sp == &Sprotocol )
	*sp = NULL;
      else
	*sp = Soutput;
    }
  }
  UNLOCK();
}


/* MT: locked by caller (openStream()) */
/* name must be registered by the caller */

static void
setFileNameStream(IOSTREAM *s, atom_t name)
{ stream_context *ctx = getStreamContext(s);

  if ( ctx->filename )
  { PL_unregister_atom(ctx->filename);
    ctx->filename = NULL_ATOM;
  }
  if ( name != NULL_ATOM )
    ctx->filename = name;
}


static atom_t
fileNameStream(IOSTREAM *s)
{ atom_t name;

  LOCK();
  name = getStreamContext(s)->filename;
  UNLOCK();

  return name;
}

#if __YAP_PROLOG__
static void
init_yap_extras(void);
#endif

void
initIO()
{ GET_LD
  const atom_t *np;
  int i;

#if __YAP_PROLOG__
  init_yap_extras();
#endif
  streamAliases = newHTable(16);
  streamContext = newHTable(16);
#ifdef __unix__
{ int fd;

  if ( (fd=Sfileno(Sinput))  < 0 || !isatty(fd) ||
       (fd=Sfileno(Soutput)) < 0 || !isatty(fd) )
    PL_set_prolog_flag("tty_control", PL_BOOL, FALSE);
}
#endif
  ResetTty();

  Sclosehook(freeStream);

  Sinput->position  = &Sinput->posbuf;	/* position logging */
  Soutput->position = &Sinput->posbuf;
  Serror->position  = &Sinput->posbuf;

  ttymode = TTY_COOKED;
  PushTty(Sinput, &ttytab, TTY_SAVE);
  LD->prompt.current = ATOM_prompt;
  PL_register_atom(ATOM_prompt);

  Suser_input  = Sinput;
  Suser_output = Soutput;
  Suser_error  = Serror;
  Scurin       = Sinput;		/* see/tell */
  Scurout      = Soutput;
  Sprotocol    = NULL;			/* protocolling */

  getStreamContext(Sinput);		/* add for enumeration */
  getStreamContext(Soutput);
  getStreamContext(Serror);
  for( i=0, np = standardStreams; *np; np++, i++ )
    addHTable(streamAliases, (void *)*np, (void *)(intptr_t)i);

  GD->io_initialised = TRUE;
}

		 /*******************************
		 *	     GET HANDLES	*
		 *******************************/

#ifdef O_PLMT

static inline IOSTREAM *
getStream(IOSTREAM *s)
{ if ( s && s->magic == SIO_MAGIC )	/* TBD: ensure visibility? */
  { Slock(s);
    return s;
  }

  return NULL;
}

static inline IOSTREAM *
tryGetStream(IOSTREAM *s)
{ if ( s && s->magic == SIO_MAGIC && StryLock(s) == 0 )
    return s;

  return NULL;
}

static inline void
releaseStream(IOSTREAM *s)
{ if ( s->magic == SIO_MAGIC )
    Sunlock(s);
}

#else /*O_PLMT*/

#define getStream(s)	(s)
#define tryGetStream(s) (s)
#define releaseStream(s)

#endif /*O_PLMT*/

int
PL_release_stream(IOSTREAM *s)
{ if ( Sferror(s) )
    return streamStatus(s);

  releaseStream(s);
  return TRUE;
}


#define SH_ERRORS   0x01		/* generate errors */
#define SH_ALIAS    0x02		/* allow alias */
#define SH_UNLOCKED 0x04		/* don't lock the stream */
#define SH_SAFE	    0x08		/* Lookup in table */

static int
get_stream_handle__LD(term_t t, IOSTREAM **s, int flags ARG_LD)
{ atom_t alias;

  if ( PL_is_functor(t, FUNCTOR_dstream1) )
  { void *p;
    term_t a = PL_new_term_ref();

    _PL_get_arg(1, t, a);
    if ( PL_get_pointer(a, &p) )
    { if ( flags & SH_SAFE )
      { Symbol symb;

	LOCK();
	symb = lookupHTable(streamContext, p);
	UNLOCK();

	if ( !symb )
	  goto noent;
      }

      if ( flags & SH_UNLOCKED )
      { if ( ((IOSTREAM *)p)->magic == SIO_MAGIC )
	{ *s = p;
	  return TRUE;
	}
	goto noent;
      }

      if ( (*s = getStream(p)) )
	return TRUE;

      goto noent;
    }
  } else if ( PL_get_atom(t, &alias) )
  { Symbol symb;

    if ( !(flags & SH_UNLOCKED) )
      LOCK();
    if ( (symb=lookupHTable(streamAliases, (void *)alias)) )
    { IOSTREAM *stream;
      uintptr_t n = (uintptr_t)symb->value;

      if ( n < 6 )			/* standard stream! */
      { stream = LD->IO.streams[n];
      } else
	stream = symb->value;

      if ( !(flags & SH_UNLOCKED) )
	UNLOCK();

      if ( stream )
      { if ( (flags & SH_UNLOCKED) )
	{ if ( stream->magic == SIO_MAGIC )
	  { *s = stream;
	    return TRUE;
	  }
	} else if ( (*s = getStream(stream)) )
	  return TRUE;
	goto noent;
      }
    }
    if ( !(flags & SH_UNLOCKED) )
      UNLOCK();

    goto noent;
  }

  if ( flags & SH_ERRORS )
    return PL_error(NULL, 0, NULL, ERR_DOMAIN,
		    (flags&SH_ALIAS) ? ATOM_stream_or_alias : ATOM_stream, t);

  return FALSE;

noent:
  if ( flags & SH_ERRORS )
    PL_error(NULL, 0, NULL, ERR_EXISTENCE, ATOM_stream, t);
  return FALSE;
}

#define get_stream_handle(t, sp, flags) \
	get_stream_handle__LD(t, sp, flags PASS_LD)

int
PL_get_stream_handle(term_t t, IOSTREAM **s)
{ GET_LD
  return get_stream_handle(t, s, SH_ERRORS|SH_ALIAS);
}


int
PL_unify_stream_or_alias(term_t t, IOSTREAM *s)
{ GET_LD
  int rval;
  stream_context *ctx;
  int i;

  if ( (i=standardStreamIndexFromStream(s)) >= 0 && i < 3 )
    return PL_unify_atom(t, standardStreams[i]);

  LOCK();
  ctx = getStreamContext(s);
  if ( ctx->alias_head )
  { rval = PL_unify_atom(t, ctx->alias_head->name);
  } else
  { term_t a = PL_new_term_ref();

    rval = ( (a=PL_new_term_ref()) &&
	     PL_put_pointer(a, s) &&
	     PL_cons_functor(a, FUNCTOR_dstream1, a) &&
	     PL_unify(t, a)
	   );
  }
  UNLOCK();

  if ( !rval && !PL_is_variable(t) )
    return PL_error(NULL, 0, "stream-argument", ERR_MUST_BE_VAR, 0);

  return rval;
}


int
PL_unify_stream(term_t t, IOSTREAM *s)
{ GET_LD
  stream_context *ctx;
  term_t a = PL_new_term_ref();

  LOCK();
  ctx = getStreamContext(s);
  UNLOCK();

  if ( !(a = PL_new_term_ref()) ||
       !PL_put_pointer(a, s) ||
       !PL_cons_functor(a, FUNCTOR_dstream1, a) )
    return FALSE;			/* resource error */

  if ( PL_unify(t, a) )
    return TRUE;
  if ( PL_is_functor(t, FUNCTOR_dstream1) )
    return FALSE;

  return PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_stream, t);
}


IOSTREAM **				/* provide access to Suser_input, */
_PL_streams(void)			/* Suser_output and Suser_error */
{ GET_LD
  return &Suser_input;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
getInputStream(term_t t, IOSTREAM **s)
getOutputStream(term_t t, IOSTREAM **s)
    These functions are the basis used by all Prolog predicates to get
    a input or output stream handle.  If t = 0, current input/output is
    returned.  This allows us to define the standard-stream based version
    simply by calling the explicit stream-based version with 0 for the
    stream argument.

    MT: The returned stream is always locked and should be returned
    using releaseStream() or streamStatus().
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
getOutputStream(term_t t, IOSTREAM **stream)
{ GET_LD
  atom_t a;
  IOSTREAM *s;

  if ( t == 0 )
  { *stream = getStream(Scurout);
    return TRUE;
  } else if ( PL_get_atom(t, &a) && a == ATOM_user )
  { *stream = getStream(Suser_output);
    return TRUE;
  } else
  { *stream = NULL;			/* make compiler happy */
  }

  if ( !PL_get_stream_handle(t, &s) )
    return FALSE;

  if ( !(s->flags &SIO_OUTPUT) )
  { releaseStream(s);
    return PL_error(NULL, 0, NULL, ERR_PERMISSION,
		    ATOM_output, ATOM_stream, t);
  }

  *stream = s;
  return TRUE;
}


static int
getInputStream__LD(term_t t, IOSTREAM **stream ARG_LD)
{ atom_t a;
  IOSTREAM *s;

  if ( t == 0 )
  { *stream = getStream(Scurin);
    return TRUE;
  } else if ( PL_get_atom(t, &a) && a == ATOM_user )
  { *stream = getStream(Suser_input);
    return TRUE;
  } else
  { *stream = NULL;			/* make compiler happy */
  }

  if ( !get_stream_handle(t, &s, SH_ERRORS|SH_ALIAS) )
    return FALSE;

  if ( !(s->flags &SIO_INPUT) )
  { releaseStream(s);
    return PL_error(NULL, 0, NULL, ERR_PERMISSION,
		    ATOM_input, ATOM_stream, t);
  }

  *stream = s;
  return TRUE;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
In windows GUI applications, the IO-streams  are   not  bound. We do not
wish to generate an error on the  stream   errors  that may be caused by
this. It is a bit of a hack, but   the alternative is to define a stream
that ignores the error. This might get hairy if the user is playing with
these streams too.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

#if defined(__WINDOWS__) || defined(__MINGW32__)
static int
isConsoleStream(IOSTREAM *s)
{ int i = standardStreamIndexFromStream(s);

  return i >= 0 && i < 3;
}
#else
#define isConsoleStream(s) FALSE
#endif


int 
reportStreamError(IOSTREAM *s)
{ if ( GD->cleaning == CLN_NORMAL &&
       !isConsoleStream(s) &&
       (s->flags & (SIO_FERR|SIO_WARN)) )
  { GET_LD
    atom_t op;
    term_t stream = PL_new_term_ref();
    char *msg;

    PL_unify_stream_or_alias(stream, s);

    if ( (s->flags & SIO_FERR) )
    { if ( s->exception )
      { fid_t fid;
	term_t ex;
	int rc;

	LD->exception.processing = TRUE;	/* allow using spare stack */
	if ( !(fid = PL_open_foreign_frame()) )
	  return FALSE;
	ex = PL_new_term_ref();
	rc = PL_recorded(s->exception, ex);
	PL_erase(s->exception);
	s->exception = NULL;
	if ( rc )
	  rc = PL_raise_exception(ex);
	PL_close_foreign_frame(fid);
	return rc;
      }

      if ( s->flags & SIO_INPUT )
      { if ( Sfpasteof(s) )
	{ return PL_error(NULL, 0, NULL, ERR_PERMISSION,
			  ATOM_input, ATOM_past_end_of_stream, stream);
	} else if ( (s->flags & SIO_TIMEOUT) )
	{ PL_error(NULL, 0, NULL, ERR_TIMEOUT,
		   ATOM_read, stream);
	  Sclearerr(s);
	  return FALSE;
	} else
	  op = ATOM_read;
      } else
	op = ATOM_write;

      if ( s->message )
      { msg = s->message;
      } else
      { msg = MSG_ERRNO;
	if ( s->io_errno )
	  errno = s->io_errno;
      }

      PL_error(NULL, 0, msg, ERR_STREAM_OP, op, stream);

      if ( (s->flags & SIO_CLEARERR) )
	Sseterr(s, SIO_FERR, NULL);

      return FALSE;
    } else
    { printMessage(ATOM_warning,
		   PL_FUNCTOR_CHARS, "io_warning", 2,
		   PL_TERM, stream,
		   PL_CHARS, s->message);

      Sseterr(s, SIO_WARN, NULL);
    }
  }

  return TRUE;
}


static int
streamStatus(IOSTREAM *s)
{ if ( (s->flags & (SIO_FERR|SIO_WARN)) )
  { releaseStream(s);
    return reportStreamError(s);
  }

  releaseStream(s);
  return TRUE;
}


		 /*******************************
		 *	     TTY MODES		*
		 *******************************/

ttybuf	ttytab;				/* saved terminal status on entry */
int	ttymode;			/* Current tty mode */

typedef struct input_context * InputContext;
typedef struct output_context * OutputContext;

struct input_context
{ IOSTREAM *    stream;                 /* pushed input */
  atom_t        term_file;              /* old term_position file */
  int           term_line;              /* old term_position line */
  InputContext  previous;               /* previous context */
};


struct output_context
{ IOSTREAM *    stream;                 /* pushed output */
  OutputContext previous;               /* previous context */
};

#define input_context_stack  (LD->IO.input_stack)
#define output_context_stack (LD->IO.output_stack)

static IOSTREAM *openStream(term_t file, term_t mode, term_t options);

void
dieIO()
{ if ( GD->io_initialised )
  { noprotocol();
    closeFiles(TRUE);
    PopTty(Sinput, &ttytab);
  }
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
closeStream() performs Prolog-level closing. Most important right now is
to to avoid closing the user-streams. If a stream cannot be flushed (due
to a write-error), an exception is  generated.

MT: We assume the stream is locked and will unlock it here.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
closeStream(IOSTREAM *s)
{ if ( s == Sinput )
  { Sclearerr(s);
    releaseStream(s);
  } else if ( s == Soutput || s == Serror )
  { if ( Sflush(s) < 0 )
      return streamStatus(s);
    releaseStream(s);
  } else
  { if ( !Sferror(s) && Sflush(s) < 0 )
    { streamStatus(s);
      Sclose(s);
      return FALSE;
    }
    if ( Sclose(s) < 0 )		/* will unlock as well */
      return FALSE;
  }

  return TRUE;
}


void
closeFiles(int all)
{ GET_LD
  TableEnum e;
  Symbol symb;

  e = newTableEnum(streamContext);
  while( (symb=advanceTableEnum(e)) )
  { IOSTREAM *s = symb->name;

    if ( all || !(s->flags & SIO_NOCLOSE) )
    { IOSTREAM *s2 = tryGetStream(s);

      if ( s2 )
      { if ( !all )
	{ term_t t = PL_new_term_ref();

	  PL_unify_stream_or_alias(t, s2);
	  printMessage(ATOM_informational,
		       PL_FUNCTOR, FUNCTOR_close_on_abort1,
		         PL_TERM, t);
	  PL_reset_term_refs(t);
	}

	closeStream(s2);
      }
    }
  }
  freeTableEnum(e);
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PL_cleanup_fork() must be called between  fork()   and  exec() to remove
traces of Prolog that are not  supposed   to  leak into the new process.
Note that we must be careful  here.   Notably,  the  code cannot lock or
unlock any mutex as the behaviour of mutexes is undefined over fork().

Earlier versions used the file-table to  close file descriptors that are
in use by Prolog. This can't work as   the  table is guarded by a mutex.
Now we use the FD_CLOEXEC flag in Snew();
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

void
PL_cleanup_fork(void)
{ stopItimer();
}


void
protocol(const char *str, size_t n)
{ GET_LD
  IOSTREAM *s;

  if ( LD && (s = getStream(Sprotocol)) )
  { while( n-- > 0 )
      Sputcode(*str++&0xff, s);
    Sflush(s);
    releaseStream(s);			/* we don not check errors */
  }
}


		 /*******************************
		 *	  TEMPORARY I/O		*
		 *******************************/


static int
push_input_context(void)
{ GET_LD
  InputContext c = allocHeap(sizeof(struct input_context));

  c->stream           = Scurin;
  c->term_file        = source_file_name;
  c->term_line        = source_line_no;
  c->previous         = input_context_stack;
  input_context_stack = c;

  return TRUE;
}


static int
pop_input_context(void)
{ GET_LD
  InputContext c = input_context_stack;

  if ( c )
  { Scurin              = c->stream;
    source_file_name    = c->term_file;
    source_line_no      = c->term_line;
    input_context_stack = c->previous;
    freeHeap(c, sizeof(struct input_context));

    return TRUE;
  } else
  { Scurin		= Sinput;
    return FALSE;
  }
}


static
PRED_IMPL("$push_input_context", 0, push_input_context, 0)
{ return push_input_context();
}


static
PRED_IMPL("$pop_input_context", 0, pop_input_context, 0)
{ return pop_input_context();
}


static void
pushOutputContext(void)
{ GET_LD
  OutputContext c = allocHeap(sizeof(struct output_context));

  c->stream            = Scurout;
  c->previous          = output_context_stack;
  output_context_stack = c;
}


static void
popOutputContext(void)
{ GET_LD
  OutputContext c = output_context_stack;

  if ( c )
  { if ( c->stream->magic == SIO_MAGIC )
      Scurout = c->stream;
    else
    { Sdprintf("Oops, current stream closed?");
      Scurout = Soutput;
    }
    output_context_stack = c->previous;
    freeHeap(c, sizeof(struct output_context));
  } else
    Scurout = Soutput;
}


int
setupOutputRedirect(term_t to, redir_context *ctx, int redir)
{ GET_LD
  atom_t a;

  ctx->term = to;
  ctx->redirected = redir;

  if ( to == 0 )
  { ctx->stream = getStream(Scurout);
    ctx->is_stream = TRUE;
  } else if ( PL_get_atom(to, &a) && a == ATOM_user )
  { ctx->stream = getStream(Suser_output);
    ctx->is_stream = TRUE;
  } else if ( get_stream_handle(to, &ctx->stream, SH_SAFE) )
  { if ( !(ctx->stream->flags &SIO_OUTPUT) )
    { releaseStream(ctx->stream);
      return PL_error(NULL, 0, NULL, ERR_PERMISSION,
		      ATOM_output, ATOM_stream, to);
    }

    ctx->is_stream = TRUE;
  } else
  { if ( PL_is_functor(to, FUNCTOR_codes2) )
    { ctx->out_format = PL_CODE_LIST;
      ctx->out_arity = 2;
    } else if ( PL_is_functor(to, FUNCTOR_codes1) )
    { ctx->out_format = PL_CODE_LIST;
      ctx->out_arity = 1;
    } else if ( PL_is_functor(to, FUNCTOR_chars2) )
    { ctx->out_format = PL_CHAR_LIST;
      ctx->out_arity = 2;
    } else if ( PL_is_functor(to, FUNCTOR_chars1) )
    { ctx->out_format = PL_CHAR_LIST;
      ctx->out_arity = 1;
    } else if ( PL_is_functor(to, FUNCTOR_string1) )
    { ctx->out_format = PL_STRING;
      ctx->out_arity = 1;
    } else if ( PL_is_functor(to, FUNCTOR_atom1) )
    { ctx->out_format = PL_ATOM;
      ctx->out_arity = 1;
    } else
    { return PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_output, to);
    }

    ctx->is_stream = FALSE;
    ctx->data = ctx->buffer;
    ctx->size = sizeof(ctx->buffer);
    ctx->stream = Sopenmem(&ctx->data, &ctx->size, "w");
    ctx->stream->encoding = ENC_WCHAR;
  }

  ctx->magic = REDIR_MAGIC;

  if ( redir )
  { pushOutputContext();
    Scurout = ctx->stream;
  }

  return TRUE;
}


int
closeOutputRedirect(redir_context *ctx)
{ int rval = TRUE;

  if ( ctx->magic != REDIR_MAGIC )
    return rval;			/* already done */
  ctx->magic = 0;

  if ( ctx->redirected )
    popOutputContext();

  if ( ctx->is_stream )
  { rval = streamStatus(ctx->stream);
  } else
  { GET_LD
    term_t out  = PL_new_term_ref();
    term_t diff, tail;

    closeStream(ctx->stream);
    _PL_get_arg(1, ctx->term, out);
    if ( ctx->out_arity == 2 )
    { diff = PL_new_term_ref();
      _PL_get_arg(2, ctx->term, diff);
      tail = PL_new_term_ref();
    } else
    { diff = tail = 0;
    }

    rval = PL_unify_wchars_diff(out, tail, ctx->out_format,
				ctx->size/sizeof(wchar_t),
				(wchar_t*)ctx->data);
    if ( rval && tail )
      rval = PL_unify(tail, diff);

    if ( ctx->data != ctx->buffer )
      Sfree(ctx->data);
  }

  return rval;
}


void
discardOutputRedirect(redir_context *ctx)
{ if ( ctx->magic != REDIR_MAGIC )
    return;				/* already done */

  ctx->magic = 0;

  if ( ctx->redirected )
    popOutputContext();

  if ( ctx->is_stream )
  { releaseStream(ctx->stream);
  } else
  { closeStream(ctx->stream);
    if ( ctx->data != ctx->buffer )
      Sfree(ctx->data);
  }
}


static
PRED_IMPL("with_output_to", 2, with_output_to, PL_FA_TRANSPARENT)
{ redir_context outctx;

  if ( setupOutputRedirect(A1, &outctx, TRUE) )
  { term_t ex = 0;
    int rval;

    if ( (rval = callProlog(NULL, A2, PL_Q_CATCH_EXCEPTION, &ex)) )
      return closeOutputRedirect(&outctx);
    discardOutputRedirect(&outctx);
    if ( ex )
      return PL_raise_exception(ex);
  }

  return FALSE;
}



void
PL_write_prompt(int dowrite)
{ GET_LD
  IOSTREAM *s = getStream(Suser_output);

  if ( s )
  { if ( dowrite )
    { atom_t a = PrologPrompt();

      if ( a )
	writeAtomToStream(s, a);
    }

    Sflush(s);
    releaseStream(s);
  }

  LD->prompt.next = FALSE;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Get a single character from Sinput  without   waiting  for a return. The
character should not be echoed.  If   PLFLAG_TTY_CONTROL  is false this
function will read the first character and  then skip all character upto
and including the newline.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
Sgetcode_intr(IOSTREAM *s, int signals)
{ int c;

#ifdef __WINDOWS__
  int newline = s->newline;
  s->newline = SIO_NL_POSIX;		/* avoid blocking \r */
#endif
  do
  { Sclearerr(s);
    c = Sgetcode(s);
  } while ( c == -1 &&
	    errno == EINTR &&
	    (!signals || PL_handle_signals() >= 0)
	  );
#ifdef __WINDOWS__
  s->newline = newline;
#endif

  return c;
}


static int
getSingleChar(IOSTREAM *stream, int signals)
{ GET_LD
  int c;
  ttybuf buf;

#if __SWI_PROLOG__
  debugstatus.suspendTrace++;
#endif
  Slock(stream);
  Sflush(stream);
  PushTty(stream, &buf, TTY_RAW);	/* just donot prompt */

  if ( !truePrologFlag(PLFLAG_TTY_CONTROL) )
  { int c2;

    c2 = Sgetcode_intr(stream, signals);
    while( c2 == ' ' || c2 == '\t' )	/* skip blanks */
      c2 = Sgetcode_intr(stream, signals);
    c = c2;
    while( c2 != EOF && c2 != '\n' )	/* read upto newline */
      c2 = Sgetcode_intr(stream, signals);
  } else
  { if ( stream->position )
    { IOPOS oldpos = *stream->position;
      c = Sgetcode_intr(stream, signals);
      *stream->position = oldpos;
    } else
      c = Sgetcode_intr(stream, signals);
  }

  if ( c == 4 || c == 26 )		/* should ask the terminal! */
    c = -1;

  PopTty(stream, &buf);
#if __SWI_PROLOG__
  debugstatus.suspendTrace--;
#endif
  Sunlock(stream);

  return c;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
readLine() reads a line from the terminal.  It is used only by the tracer.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

#ifndef DEL
#define DEL 127
#endif

int
readLine(IOSTREAM *in, IOSTREAM *out, char *buffer)
{ GET_LD
  int c;
  char *buf = &buffer[strlen(buffer)];
  ttybuf tbuf;

  Slock(in);
  Slock(out);

  PushTty(in, &tbuf, TTY_RAW);		/* just donot prompt */

  for(;;)
  { Sflush(out);

    switch( (c=Sgetcode_intr(in, FALSE)) )
    { case '\n':
      case '\r':
      case EOF:
        *buf++ = EOS;
        PopTty(in, &tbuf);
	Sunlock(in);
	Sunlock(out);

	return c == EOF ? FALSE : TRUE;
      case '\b':
      case DEL:
	if ( truePrologFlag(PLFLAG_TTY_CONTROL) && buf > buffer )
	{ Sfputs("\b \b", out);
	  buf--;
	  continue;
	}
      default:
	if ( truePrologFlag(PLFLAG_TTY_CONTROL) )
	  Sputcode(c, out);
	*buf++ = c;
    }
  }
}


IOSTREAM *
PL_current_input()
{ GET_LD
  return getStream(Scurin);
}


IOSTREAM *
PL_current_output()
{ GET_LD
  return getStream(Scurout);
}


static int
openProtocol(term_t f, int appnd)
{ GET_LD
  IOSTREAM *s;
  term_t mode = PL_new_term_ref();

  noprotocol();

  PL_put_atom(mode, appnd ? ATOM_append : ATOM_write);
  if ( (s = openStream(f, mode, 0)) )
  { s->flags |= SIO_NOCLOSE;		/* do not close on abort */

    Sprotocol = s;
    Suser_input->tee = s;
    Suser_output->tee = s;
    Suser_error->tee = s;

    return TRUE;
  }

  return FALSE;
}


static int
noprotocol(void)
{ GET_LD
  IOSTREAM *s;

  if ( (s = getStream(Sprotocol)) )
  { TableEnum e;
    Symbol symb;

    e = newTableEnum(streamContext);
    while( (symb=advanceTableEnum(e)) )
    { IOSTREAM *p = symb->name;

      if ( p->tee == s )
	p->tee = NULL;
    }
    freeTableEnum(e);

    closeStream(s);
    Sprotocol = NULL;
  }

  return TRUE;
}


static
PRED_IMPL("noprotocol", 0, noprotocol, 0)
{ return noprotocol();
}


		 /*******************************
		 *	 STREAM ATTRIBUTES	*
		 *******************************/


static
PRED_IMPL("set_stream", 2, set_stream, 0)
{ PRED_LD
  IOSTREAM *s;
  atom_t aname;
  int arity;

  term_t stream = A1;
  term_t attr = A2;

  if ( !PL_get_stream_handle(stream, &s) )
    return FALSE;

  if ( PL_get_name_arity(attr, &aname, &arity) )
  { if ( arity == 1 )
    { term_t a = PL_new_term_ref();

      _PL_get_arg(1, attr, a);

      if ( aname == ATOM_alias )	/* alias(name) */
      { atom_t alias;
	int i;

	if ( !PL_get_atom_ex(a, &alias) )
	  goto error;

	if ( (i=standardStreamIndexFromName(alias)) >= 0 )
	{ LD->IO.streams[i] = s;
	  if ( i == 0 )
	    LD->prompt.next = TRUE;	/* changed standard input: prompt! */
	  goto ok;
	}

	LOCK();
	aliasStream(s, alias);
	UNLOCK();
	goto ok;
      } else if ( aname == ATOM_buffer ) /* buffer(Buffering) */
      { atom_t b;

#define SIO_ABUF (SIO_FBUF|SIO_LBUF|SIO_NBUF)
	if ( !PL_get_atom_ex(a, &b) )
	  goto error;
	if ( b == ATOM_full )
	{ s->flags &= ~SIO_ABUF;
	  s->flags |= SIO_FBUF;
	} else if ( b == ATOM_line )
	{ s->flags &= ~SIO_ABUF;
	  s->flags |= SIO_LBUF;
	} else if ( b == ATOM_false )
	{ Sflush(s);
	  s->flags &= ~SIO_ABUF;
	  s->flags |= SIO_NBUF;
	} else
	{ PL_error("set_stream", 2, NULL, ERR_DOMAIN,
		   ATOM_buffer, a);
	  goto error;
	}
	goto ok;
      } else if ( aname == ATOM_buffer_size )
      { int size;

	if ( !PL_get_integer_ex(a, &size) )
	  goto error;
	if ( size < 1 )
	{ PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_not_less_than_one, a);
	  goto error;
	}
	Ssetbuffer(s, NULL, size);
	goto ok;
      } else if ( aname == ATOM_eof_action ) /* eof_action(Action) */
      { atom_t action;

	if ( !PL_get_atom_ex(a, &action) )
	  return FALSE;
	if ( action == ATOM_eof_code )
	{ s->flags &= ~(SIO_NOFEOF|SIO_FEOF2ERR);
	} else if ( action == ATOM_reset )
	{ s->flags &= ~SIO_FEOF2ERR;
	  s->flags |= SIO_NOFEOF;
	} else if ( action == ATOM_error )
	{ s->flags &= ~SIO_NOFEOF;
	  s->flags |= SIO_FEOF2ERR;
	} else
	{ PL_error("set_stream", 2, NULL, ERR_DOMAIN,
		   ATOM_eof_action, a);
	  goto error;
	}

	goto ok;
      } else if ( aname == ATOM_type ) /* type(Type) */
      { atom_t type;

	if ( !PL_get_atom_ex(a, &type) )
	  return FALSE;
	if ( type == ATOM_text )
	{ s->flags |= SIO_TEXT;
	} else if ( type == ATOM_binary )
	{ s->flags &= ~SIO_TEXT;
	} else
	{ PL_error("set_stream", 2, NULL, ERR_DOMAIN,
		   ATOM_type, a);
	  goto error;
	}

	goto ok;
      } else if ( aname == ATOM_close_on_abort ) /* close_on_abort(Bool) */
      { int close;

	if ( !PL_get_bool_ex(a, &close) )
	  goto error;

	if ( close )
	  s->flags &= ~SIO_NOCLOSE;
	else
	  s->flags |= SIO_NOCLOSE;

	goto ok;
      } else if ( aname == ATOM_record_position )
      { int rec;

	if ( !PL_get_bool_ex(a, &rec) )
	  goto error;

	if ( rec )
	  s->position = &s->posbuf;
	else
	  s->position = NULL;

	goto ok;
      } else if ( aname == ATOM_file_name ) /* file_name(Atom) */
      {	atom_t fn;

	if ( !PL_get_atom_ex(a, &fn) )
	  goto error;

	PL_register_atom(fn);
	LOCK();
	setFileNameStream(s, fn);
	UNLOCK();

	goto ok;
      } else if ( aname == ATOM_timeout )
      { double f;
	atom_t v;

	if ( PL_get_atom(a, &v) && v == ATOM_infinite )
	{ s->timeout = -1;
	  goto ok;
	}
	if ( !PL_get_float_ex(a, &f) )
	  goto error;

	s->timeout = (int)(f*1000.0);
	if ( s->timeout < 0 )
	  s->timeout = 0;
	goto ok;
      } else if ( aname == ATOM_tty )	/* tty(bool) */
      {	int val;

	if ( !PL_get_bool_ex(a, &val) )
	  goto error;

	if ( val )
	  set(s, SIO_ISATTY);
	else
	  clear(s, SIO_ISATTY);

	goto ok;
      } else if ( aname == ATOM_encoding )	/* encoding(atom) */
      {	atom_t val;
	IOENC enc;

	if ( !PL_get_atom_ex(a, &val) )
	  goto error;
	if ( (enc = atom_to_encoding(val)) == ENC_UNKNOWN )
	{ bad_encoding(NULL, val);
	  goto error;
	}

	if ( Ssetenc(s, enc, NULL) == 0 )
	  goto ok;

	PL_error(NULL, 0, NULL, ERR_PERMISSION,
		 ATOM_encoding, ATOM_stream, stream);
	goto error;
      } else if ( aname == ATOM_representation_errors )
      { atom_t val;

	if ( !PL_get_atom_ex(a, &val) )
	  goto error;
	clear(s, SIO_REPXML|SIO_REPPL);
	if ( val == ATOM_error )
	  ;
	else if ( val == ATOM_xml )
	  set(s, SIO_REPXML);
	else if ( val == ATOM_prolog )
	  set(s, SIO_REPPL);
	else
	{ PL_error(NULL, 0, NULL, ERR_DOMAIN,
		   ATOM_representation_errors, a);
	  goto error;
	}
	goto ok;
      } else if ( aname == ATOM_newline )
      { atom_t val;

	if ( !PL_get_atom_ex(a, &val) )
	  goto error;
	if ( val == ATOM_posix )
	  s->newline = SIO_NL_POSIX;
	else if ( val == ATOM_dos )
	  s->newline = SIO_NL_DOS;
	else if ( val == ATOM_detect )
	{ if ( false(s, SIO_INPUT) )
	  { PL_error(NULL, 0, "detect only allowed for input streams",
		     ERR_DOMAIN, ATOM_newline, a);
	    goto error;
	  }
	  s->newline = SIO_NL_DETECT;
	} else
	{ PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_newline, a);
	  goto error;
	}
	goto ok;
      }
    }
  }

  PL_error("set_stream", 2, NULL, ERR_TYPE,
	   PL_new_atom("stream_attribute"), attr);
  goto error;

ok:
  releaseStream(s);
  return TRUE;
error:
  releaseStream(s);
  return FALSE;
}


		/********************************
		*          STRING I/O           *
		*********************************/

extern IOFUNCTIONS Smemfunctions;

int
tellString(char **s, size_t *size, IOENC enc)
{ GET_LD
  IOSTREAM *stream;

  stream = Sopenmem(s, size, "w");
  stream->encoding = enc;
  pushOutputContext();
  Scurout = stream;

  return TRUE;
}


int
toldString()
{ GET_LD
  IOSTREAM *s = getStream(Scurout);

  if ( !s )
    return TRUE;

  if ( s->functions == &Smemfunctions )
  { closeStream(s);
    popOutputContext();
  } else
    releaseStream(s);

  return TRUE;
}


		/********************************
		*       WAITING FOR INPUT	*
		********************************/

#ifndef HAVE_SELECT

static
PRED_IMPL("wait_for_input", 3, wait_for_input, 0)
{ return notImplemented("wait_for_input", 3);
}

#else

typedef struct fdentry
{ int fd;
  term_t stream;
  struct fdentry *next;
} fdentry;


static inline term_t
findmap(fdentry *map, int fd)
{ for( ; map; map = map->next )
  { if ( map->fd == fd )
      return map->stream;
  }
  assert(0);
  return 0;
}


static
PRED_IMPL("wait_for_input", 3, wait_for_input, 0)
{ PRED_LD
  fd_set fds;
  struct timeval t, *to;
  double time;
  int n, max = 0, ret, min = 1 << (INTBITSIZE-2);
  fdentry *map     = NULL;
  term_t head      = PL_new_term_ref();
  term_t streams   = PL_copy_term_ref(A1);
  term_t available = PL_copy_term_ref(A2);
  term_t ahead     = PL_new_term_ref();
  int from_buffer  = 0;
  atom_t a;

  term_t timeout = A3;

  FD_ZERO(&fds);
  while( PL_get_list(streams, head, streams) )
  { IOSTREAM *s;
    int fd;
    fdentry *e;

    if ( !PL_get_stream_handle(head, &s) )
      return FALSE;
    if ( (fd=Sfileno(s)) < 0 )
    { releaseStream(s);
      return PL_error("wait_for_input", 3, NULL, ERR_DOMAIN,
		      PL_new_atom("file_stream"), head);
    }
    releaseStream(s);
					/* check for input in buffer */
    if ( s->bufp < s->limitp )
    { if ( !PL_unify_list(available, ahead, available) ||
	   !PL_unify(ahead, head) )
	return FALSE;
      from_buffer++;
    }

    e         = alloca(sizeof(*e));
    e->fd     = fd;
    e->stream = PL_copy_term_ref(head);
    e->next   = map;
    map       = e;

#ifdef __WINDOWS__
    FD_SET((SOCKET)fd, &fds);
#else
    FD_SET(fd, &fds);
#endif

    if ( fd > max )
      max = fd;
    if( fd < min )
      min = fd;
  }
  if ( !PL_get_nil(streams) )
    return PL_error("wait_for_input", 3, NULL, ERR_TYPE, ATOM_list, A1);

  if ( from_buffer > 0 )
    return PL_unify_nil(available);

  if ( PL_get_atom(timeout, &a) && a == ATOM_infinite )
  { to = NULL;
  } else if ( PL_is_integer(timeout) )
  { long v;

    PL_get_long(timeout, &v);
    if ( v > 0L )
    { t.tv_sec = v;
      t.tv_usec = 0;
      to = &t;
    } else if ( v == 0 )
    { to = NULL;
    } else
    { t.tv_sec  = 0;
      t.tv_usec = 0;
      to = &t;
    }
  } else
  { if ( !PL_get_float(timeout, &time) )
      return PL_error("wait_for_input", 3, NULL,
		      ERR_TYPE, ATOM_float, timeout);

    if ( time >= 0.0 )
    { t.tv_sec  = (int)time;
      t.tv_usec = ((int)(time * 1000000) % 1000000);
    } else
    { t.tv_sec  = 0;
      t.tv_usec = 0;
    }
    to = &t;
  }

  while( (ret=select(max+1, &fds, NULL, NULL, to)) == -1 &&
	 errno == EINTR )
  { fdentry *e;

    if ( PL_handle_signals() < 0 )
      return FALSE;				/* exception */

    FD_ZERO(&fds);			/* EINTR may leave fds undefined */
    for(e=map; e; e=e->next)		/* so we rebuild it to be safe */
    {
#ifdef __WINDOWS__
      FD_SET((SOCKET)e->fd, &fds);
#else
      FD_SET(e->fd, &fds);
#endif
    }
  }

  switch(ret)
  { case -1:
      return PL_error("wait_for_input", 3, MSG_ERRNO, ERR_FILE_OPERATION,
		      ATOM_select, ATOM_stream, A1);

    case 0: /* Timeout */
      break;

    default: /* Something happend -> check fds */
      for(n=min; n <= max; n++)
      { if ( FD_ISSET(n, &fds) )
	{ if ( !PL_unify_list(available, ahead, available) ||
	       !PL_unify(ahead, findmap(map, n)) )
	    return FALSE;
	}
      }
      break;
  }

  return PL_unify_nil(available);
}

#endif /* HAVE_SELECT */


		/********************************
		*      PROLOG CONNECTION        *
		*********************************/

#define MAX_PENDING SIO_BUFSIZE		/* 4096 */

static void
re_buffer(IOSTREAM *s, const char *from, size_t len)
{ if ( s->bufp < s->limitp )
  { size_t size = s->limitp - s->bufp;

    memmove(s->buffer, s->bufp, size);
    s->bufp = s->buffer;
    s->limitp = &s->bufp[size];
  } else
  { s->bufp = s->limitp = s->buffer;
  }

  memcpy(s->bufp, from, len);
  s->bufp += len;
}


#ifndef HAVE_MBSNRTOWCS
static size_t
mbsnrtowcs(wchar_t *dest, const char **src,
	   size_t nms, size_t len, mbstate_t *ps)
{ wchar_t c;
  const char *us = *src;
  const char *es = us+nms;
  size_t count = 0;

  assert(dest == NULL);			/* incomplete implementation */

  while(us<es)
  { size_t skip = mbrtowc(&c, us, es-us, ps);

    if ( skip == (size_t)-1 )		/* error */
    { DEBUG(1, Sdprintf("mbsnrtowcs(): bad multibyte seq\n"));
      return skip;
    }
    if ( skip == (size_t)-2 )		/* incomplete */
    { *src = us;
      return count;
    }

    count++;
    us += skip;
  }

  *src = us;
  return count;
}
#else
#if defined(HAVE_DECL_MBSNRTOWCS) && !HAVE_DECL_MBSNRTOWCS
size_t mbsnrtowcs(wchar_t *dest, const char **src,
		  size_t nms, size_t len, mbstate_t *ps);
#endif
#endif /*HAVE_MBSNRTOWCS*/

static int
skip_cr(IOSTREAM *s)
{ if ( s->flags&SIO_TEXT )
  { switch(s->newline)
    { case SIO_NL_DETECT:
	s->newline = SIO_NL_DOS;
        /*FALLTHROUGH*/
      case SIO_NL_DOS:
	return TRUE;
    }
  }
  return FALSE;
}


static
PRED_IMPL("read_pending_input", 3, read_pending_input, 0)
{ PRED_LD
  IOSTREAM *s;

  if ( getInputStream(A1, &s) )
  { char buf[MAX_PENDING];
    ssize_t n;
    int64_t off0 = Stell64(s);
    IOPOS pos0;
    list_ctx ctx;

    if ( Sferror(s) )
      return streamStatus(s);

    n = Sread_pending(s, buf, sizeof(buf), 0);
    if ( n < 0 )			/* should not happen */
      return streamStatus(s);
    if ( n == 0 )			/* end-of-file */
    { S__fcheckpasteeof(s, -1);
      return PL_unify(A2, A3);
    }
    if ( s->position )
    { pos0 = *s->position;
    } else
    { memset(&pos0, 0, sizeof(pos0));	/* make compiler happy */
    }

    switch(s->encoding)
    { case ENC_OCTET:
      case ENC_ISO_LATIN_1:
      case ENC_ASCII:
      { ssize_t i;

	if ( !allocList(n, &ctx) )
	  return FALSE;

	for(i=0; i<n; i++)
	{ int c = buf[i]&0xff;

	  if ( c == '\r' && skip_cr(s) )
	    continue;

	  if ( s->position )
	    S__fupdatefilepos_getc(s, c);

	  addSmallIntList(&ctx, c);
	}
	if ( s->position )
	  s->position->byteno = pos0.byteno+n;

	break;
      }
      case ENC_ANSI:
      { size_t count, i;
	mbstate_t s0;
	const char *us = buf;
	const char *es = buf+n;

	if ( !s->mbstate )
	{ if ( !(s->mbstate = malloc(sizeof(*s->mbstate))) )
	  { PL_error(NULL, 0, NULL, ERR_NOMEM);
	    goto failure;
	  }
	  memset(s->mbstate, 0, sizeof(*s->mbstate));
	}
	s0 = *s->mbstate;
	count = mbsnrtowcs(NULL, &us, n, 0, &s0);
	if ( count == (size_t)-1 )
	{ Sseterr(s, SIO_WARN, "Illegal multibyte Sequence");
	  goto failure;
	}

	DEBUG(2, Sdprintf("Got %ld codes from %d bytes; incomplete: %ld\n",
			  count, n, es-us));

	if ( !allocList(count, &ctx) )
	  return FALSE;

	for(us=buf,i=0; i<count; i++)
	{ wchar_t c;

	  us += mbrtowc(&c, us, es-us, s->mbstate);
	  if ( c == '\r' && skip_cr(s) )
	    continue;
    	  if ( s->position )
	    S__fupdatefilepos_getc(s, c);

	  addSmallIntList(&ctx, c);
	}
	if ( s->position )
	  s->position->byteno = pos0.byteno+us-buf;

	re_buffer(s, us, es-us);
        break;
      }
      case ENC_UTF8:
      { const char *us = buf;
	const char *es = buf+n;
	size_t count = 0, i;

	while(us<es)
	{ const char *ec = us + UTF8_FBN(us[0]) + 1;

	  if ( ec <= es )
	  { count++;
	    us=ec;
	  } else
	    break;
	}

	DEBUG(2, Sdprintf("Got %ld codes from %d bytes; incomplete: %ld\n",
			  count, n, es-us));

	if ( !allocList(count, &ctx) )
	  return FALSE;

	for(us=buf,i=0; i<count; i++)
	{ int c;

	  us = utf8_get_char(us, &c);
	  if ( c == '\r' && skip_cr(s) )
	    continue;
    	  if ( s->position )
	    S__fupdatefilepos_getc(s, c);

	  addSmallIntList(&ctx, c);
	}
	if ( s->position )
	  s->position->byteno = pos0.byteno+us-buf;

	re_buffer(s, us, es-us);
        break;
      }
      case ENC_UNICODE_BE:
      case ENC_UNICODE_LE:
      { size_t count = (size_t)n/2;
	const char *us = buf;
	size_t done, i;

	if ( !allocList(count, &ctx) )
	  return FALSE;

	for(i=0; i<count; us+=2, i++)
	{ int c;

	  if ( s->encoding == ENC_UNICODE_BE )
	    c = ((us[0]&0xff)<<8)+(us[1]&0xff);
	  else
	    c = ((us[1]&0xff)<<8)+(us[0]&0xff);
	  if ( c == '\r' && skip_cr(s) )
	    continue;

	  if ( s->position )
	    S__fupdatefilepos_getc(s, c);

	  addSmallIntList(&ctx, c);
	}

	done = count*2;
	if ( s->position )
	  s->position->byteno = pos0.byteno+done;
	re_buffer(s, buf+done, n-done);
        break;
      }
      case ENC_WCHAR:
      { const pl_wchar_t *ws = (const pl_wchar_t*)buf;
	size_t count = (size_t)n/sizeof(pl_wchar_t);
	size_t done, i;

	if ( !allocList(count, &ctx) )
	  return FALSE;

	for(i=0; i<count; i++)
	{ int c = ws[i];

	  if ( c == '\r' && skip_cr(s) )
	    continue;
	  if ( s->position )
	    S__fupdatefilepos_getc(s, c);

	  addSmallIntList(&ctx, c);
	}

	done = count*sizeof(pl_wchar_t);
	if ( s->position )
	  s->position->byteno = pos0.byteno+done;
	re_buffer(s, buf+done, n-done);
        break;
      }
      case ENC_UNKNOWN:
      default:
	assert(0);
        return FALSE;
    }

    if ( !unifyDiffList(A2, A3, &ctx) )
      goto failure;

    releaseStream(s);
    return TRUE;

  failure:
    Sseek64(s, off0, SIO_SEEK_SET);	/* TBD: error? */
    if ( s->position )
      *s->position = pos0;
    releaseStream(s);
    return FALSE;
  }

  return FALSE;
}


static foreign_t
put_byte(term_t stream, term_t byte ARG_LD)
{ IOSTREAM *s;
  int c;

  if ( !PL_get_integer(byte, &c) || c < 0 || c > 255 )
    return PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_byte, byte);
  if ( !getOutputStream(stream, &s) )
    return FALSE;

  Sputc(c, s);

  return streamStatus(s);
}


static
PRED_IMPL("put_byte", 2, put_byte2, 0)
{ PRED_LD

  return put_byte(A1, A2 PASS_LD);
}


static
PRED_IMPL("put_byte", 1, put_byte1, 0)
{ PRED_LD

  return put_byte(0, A1 PASS_LD);
}


static foreign_t
put_code(term_t stream, term_t chr ARG_LD)
{ IOSTREAM *s;
  int c = 0;

  if ( !PL_get_char(chr, &c, FALSE) )
    return FALSE;
  if ( !getOutputStream(stream, &s) )
    return FALSE;

  Sputcode(c, s);

  return streamStatus(s);
}


static
PRED_IMPL("put_code", 2, put_code2, 0)
{ PRED_LD

  return put_code(A1, A2 PASS_LD);
}


static
PRED_IMPL("put_code", 1, put_code1, 0)
{ PRED_LD

  return put_code(0, A1 PASS_LD);
}


static
PRED_IMPL("put", 2, put2, 0)
{ PRED_LD

  return put_code(A1, A2 PASS_LD);
}


static
PRED_IMPL("put", 1, put1, 0)
{ PRED_LD

  return put_code(0, A1 PASS_LD);
}


static foreign_t
get_nonblank(term_t in, term_t chr ARG_LD)
{ IOSTREAM *s;

  if ( getInputStream(in, &s) )
  { int c;

    for(;;)
    { c = Sgetcode(s);

      if ( c == EOF )
      { TRY(PL_unify_integer(chr, -1));
	return streamStatus(s);
      }

      if ( !isBlankW(c) )
      { releaseStream(s);
	return PL_unify_integer(chr, c);
      }
    }
  }

  return FALSE;
}


static
PRED_IMPL("get", 1, get1, 0)
{ PRED_LD

  return get_nonblank(0, A1 PASS_LD);
}


static
PRED_IMPL("get", 2, get2, 0)
{ PRED_LD

  return get_nonblank(A1, A2 PASS_LD);
}


static foreign_t
skip(term_t in, term_t chr ARG_LD)
{ int c = -1;
  int r;
  IOSTREAM *s;

  if ( !PL_get_char(chr, &c, FALSE) )
    return FALSE;
  if ( !getInputStream(in, &s) )
    return FALSE;

  while((r=Sgetcode(s)) != c && r != EOF )
    ;

  return streamStatus(s);
}


static
PRED_IMPL("skip", 1, skip1, 0)
{ PRED_LD

  return skip(0, A1 PASS_LD);
}


static
PRED_IMPL("skip", 2, skip2, 0)
{ PRED_LD

  return skip(A1, A2 PASS_LD);
}


static
PRED_IMPL("get_single_char", 1, get_single_char, 0)
{ GET_LD
  IOSTREAM *s = getStream(Suser_input);
  int c = getSingleChar(s, TRUE);

  if ( c == EOF )
  { if ( PL_exception(0) )
    { releaseStream(s);
      return FALSE;
    }

    PL_unify_integer(A1, -1);
    return streamStatus(s);
  }

  releaseStream(s);

  return PL_unify_integer(A1, c);
}


static foreign_t
get_byte2(term_t in, term_t chr ARG_LD)
{ IOSTREAM *s;

  if ( getInputStream(in, &s) )
  { int c = Sgetc(s);

    if ( PL_unify_integer(chr, c) )
      return streamStatus(s);

    if ( Sferror(s) )
      return streamStatus(s);

    PL_get_char(chr, &c, TRUE);		/* set type-error */
  }

  return FALSE;
}


static
PRED_IMPL("get_byte", 2, get_byte2, 0)
{ PRED_LD

  return get_byte2(A1, A2 PASS_LD);
}


static
PRED_IMPL("get_byte", 1, get_byte1, 0)
{ PRED_LD

  return get_byte2(0, A1 PASS_LD);
}


static foreign_t
get_code2(term_t in, term_t chr ARG_LD)
{ IOSTREAM *s;

  if ( getInputStream(in, &s) )
  { int c = Sgetcode(s);

    if ( PL_unify_integer(chr, c) )
      return streamStatus(s);

    if ( Sferror(s) )
      return streamStatus(s);

    PL_get_char(chr, &c, TRUE);		/* set type-error */
    releaseStream(s);
  }

  return FALSE;
}


static
PRED_IMPL("get_code", 2, get_code2, 0)
{ PRED_LD
  return get_code2(A1, A2 PASS_LD);
}


static
PRED_IMPL("get_code", 1, get_code1, 0)
{ PRED_LD
  return get_code2(0, A1 PASS_LD);
}


static foreign_t
get_char2(term_t in, term_t chr ARG_LD)
{ IOSTREAM *s;

  if ( getInputStream(in, &s) )
  { int c = Sgetcode(s);

    if ( PL_unify_atom(chr, c == -1 ? ATOM_end_of_file : codeToAtom(c)) )
      return streamStatus(s);

    if ( Sferror(s) )
      return streamStatus(s);

    PL_get_char(chr, &c, TRUE);		/* set type-error */
    releaseStream(s);
  }

  return FALSE;
}


static
PRED_IMPL("get_char", 2, get_char2, 0)
{ PRED_LD
  return get_char2(A1, A2 PASS_LD);
}


static
PRED_IMPL("get_char", 1, get_char1, 0)
{ PRED_LD
  return get_char2(0, A1 PASS_LD);
}


static
PRED_IMPL("ttyflush", 0, ttyflush, 0)
{ PRED_LD
  IOSTREAM *s = getStream(Suser_output);

  Sflush(s);

  return streamStatus(s);
}


static
PRED_IMPL("protocol", 1, protocol, 0)
{ return openProtocol(A1, FALSE);
}


static
PRED_IMPL("protocola", 1, protocola, 0)
{ return openProtocol(A1, TRUE);
}


static
PRED_IMPL("protocolling", 1, protocolling, 0)
{ PRED_LD
  IOSTREAM *s;

  if ( (s = Sprotocol) )
  { atom_t a;

    if ( (a = fileNameStream(s)) )
      return PL_unify_atom(A1, a);
    else
      return PL_unify_stream_or_alias(A1, s);
  }

  return FALSE;
}


static
PRED_IMPL("prompt", 2, prompt, 0)
{ PRED_LD
  atom_t a;

  term_t old = A1;
  term_t new = A2;

  if ( PL_unify_atom(old, LD->prompt.current) &&
       PL_get_atom(new, &a) )
  { if ( LD->prompt.current )
      PL_unregister_atom(LD->prompt.current);
    LD->prompt.current = a;
    PL_register_atom(a);
    return TRUE;
  }

  return FALSE;
}


static void
prompt1(atom_t prompt)
{ GET_LD

  if ( LD->prompt.first != prompt )
  { if ( LD->prompt.first )
      PL_unregister_atom(LD->prompt.first);
    LD->prompt.first = prompt;
    PL_register_atom(LD->prompt.first);
  }

  LD->prompt.first_used = FALSE;
}


static
PRED_IMPL("prompt1", 1, prompt1, 0)
{ GET_LD
  atom_t a;
  PL_chars_t txt;

  if ( PL_get_atom(A1, &a) )
  { prompt1(a);
  } else if ( PL_get_text(A1, &txt,  CVT_ALL|CVT_EXCEPTION) )
  { prompt1(textToAtom(&txt));
  } else
    return FALSE;

  return TRUE;
}


atom_t
PrologPrompt()
{ GET_LD

  if ( !LD->prompt.first_used && LD->prompt.first )
  { LD->prompt.first_used = TRUE;

    return LD->prompt.first;
  }

  if ( Sinput->position && Sinput->position->linepos == 0 )
    return LD->prompt.current;
  else
    return 0;				/* "" */
}


static int
tab(term_t out, term_t spaces)
{ int64_t count;
  IOSTREAM *s;

  if ( !getOutputStream(out, &s) )
    return FALSE;
  if ( !PL_eval_expression_to_int64_ex(spaces, &count) )
    return FALSE;

  while(count-- > 0)
  { if ( Sputcode(' ', s) < 0 )
      break;
  }

  return streamStatus(s);
}


static
PRED_IMPL("tab", 2, tab2, 0)
{ return tab(A1, A2);
}

static
PRED_IMPL("tab", 1, tab1, 0)
{ return tab(0, A1);
}


		 /*******************************
		 *	      ENCODING		*
		 *******************************/


static struct encname
{ IOENC  code;
  atom_t name;
} encoding_names[] =
{ { ENC_UNKNOWN,     ATOM_unknown },
  { ENC_OCTET,       ATOM_octet },
  { ENC_ASCII,       ATOM_ascii },
  { ENC_ISO_LATIN_1, ATOM_iso_latin_1 },
  { ENC_ANSI,	     ATOM_text },
  { ENC_UTF8,        ATOM_utf8 },
  { ENC_UNICODE_BE,  ATOM_unicode_be },
  { ENC_UNICODE_LE,  ATOM_unicode_le },
  { ENC_WCHAR,	     ATOM_wchar_t },
  { ENC_UNKNOWN,     0 },
};


IOENC
atom_to_encoding(atom_t a)
{ struct encname *en;

  for(en=encoding_names; en->name; en++)
  { if ( en->name == a )
      return en->code;
  }

  return ENC_UNKNOWN;
}


static atom_t
encoding_to_atom(IOENC enc)
{ return encoding_names[enc].name;
}


static int
bad_encoding(const char *msg, atom_t name)
{ GET_LD
  term_t t = PL_new_term_ref();

  PL_put_atom(t, name);
  return PL_error(NULL, 0, msg, ERR_DOMAIN, ATOM_encoding, t);
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
fn_to_atom() translates a 8-bit  filename  into   a  unicode  atom.  The
encoding is generic `multibyte' on Unix systems   and  fixed to UTF-8 on
Windows, where the uxnt layer  translates   the  UTF-8  sequences to the
Windows *W() functions.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static atom_t
fn_to_atom(const char *fn)
{ PL_chars_t text;
  atom_t a;

  text.text.t    = (char *)fn;
  text.encoding  = ((REP_FN&REP_UTF8) ? ENC_UTF8 :
		    (REP_FN&REP_MB)   ? ENC_ANSI : ENC_ISO_LATIN_1);
  text.storage   = PL_CHARS_HEAP;
  text.length    = strlen(fn);
  text.canonical = FALSE;

  a = textToAtom(&text);
  PL_free_text(&text);

  return a;
}


		/********************************
		*       STREAM BASED I/O        *
		*********************************/
static const opt_spec open4_options[] =
{ { ATOM_type,		 OPT_ATOM },
  { ATOM_reposition,     OPT_BOOL },
  { ATOM_alias,	         OPT_ATOM },
  { ATOM_eof_action,     OPT_ATOM },
  { ATOM_close_on_abort, OPT_BOOL },
  { ATOM_buffer,	 OPT_ATOM },
  { ATOM_lock,		 OPT_ATOM },
  { ATOM_encoding,	 OPT_ATOM },
  { ATOM_bom,	 	 OPT_BOOL },
  { NULL_ATOM,	         0 }
};

IOSTREAM *
openStream(term_t file, term_t mode, term_t options)
{ GET_LD
  atom_t mname;
  atom_t type           = ATOM_text;
  int    reposition     = TRUE;
  atom_t alias	        = NULL_ATOM;
  atom_t eof_action     = ATOM_eof_code;
  atom_t buffer         = ATOM_full;
  atom_t lock		= ATOM_none;
  atom_t encoding	= NULL_ATOM;
  int    close_on_abort = TRUE;
  int	 bom		= -1;
  char   how[10];
  char  *h		= how;
  char *path;
  IOSTREAM *s;
  IOENC enc;

  if ( options )
  { if ( !scan_options(options, 0, ATOM_stream_option, open4_options,
		       &type, &reposition, &alias, &eof_action,
		       &close_on_abort, &buffer, &lock, &encoding, &bom) )
      return FALSE;
  }

					/* MODE */
  if ( PL_get_atom(mode, &mname) )
  { if ( mname == ATOM_write )
    { *h++ = 'w';
    } else if ( mname == ATOM_append )
    { bom = FALSE;
      *h++ = 'a';
    } else if ( mname == ATOM_update )
    { bom = FALSE;
      *h++ = 'u';
    } else if ( mname == ATOM_read )
    { *h++ = 'r';
    } else
    { PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_io_mode, mode);
      return NULL;
    }
  } else
  { PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_atom, mode);
    return NULL;
  }

					/* ENCODING */
  if ( encoding != NULL_ATOM )
  { enc = atom_to_encoding(encoding);
    if ( enc == ENC_UNKNOWN )
    { bad_encoding(NULL, encoding);
      return NULL;
    }
    if ( type == ATOM_binary && enc != ENC_OCTET )
    { bad_encoding("type(binary) implies encoding(octet)", encoding);
      return NULL;
    }
    switch(enc)				/* explicitely specified: do not */
    { case ENC_OCTET:			/* switch to Unicode.  For implicit */
      case ENC_ASCII:			/* and unicode types we must detect */
      case ENC_ISO_LATIN_1:		/* and skip the BOM */
      case ENC_WCHAR:
	bom = FALSE;
        break;
      default:
	;
    }
  } else if ( type == ATOM_binary )
  { enc = ENC_OCTET;
    bom = FALSE;
  } else
  { enc = LD->encoding;
  }

  if ( bom == -1 )
    bom = (mname == ATOM_read ? TRUE : FALSE);
  if ( type == ATOM_binary )
    *h++ = 'b';

					/* LOCK */
  if ( lock != ATOM_none )
  { *h++ = 'l';
    if ( lock == ATOM_read || lock == ATOM_shared )
      *h++ = 'r';
    else if ( lock == ATOM_write || lock == ATOM_exclusive )
      *h++ = 'w';
    else
    { term_t l = PL_new_term_ref();
      PL_put_atom(l, lock);
      PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_lock, l);
      return NULL;
    }
  }

  *h = EOS;

					/* FILE */
  if ( PL_get_chars(file, &path,
		    CVT_ATOM|CVT_STRING|CVT_EXCEPTION|REP_FN) )
  { if ( !(s = Sopen_file(path, how)) )
    { PL_error(NULL, 0, OsError(), ERR_FILE_OPERATION,
	       ATOM_open, ATOM_source_sink, file);
      return NULL;
    }
    setFileNameStream(s, fn_to_atom(path));
  }
#ifdef HAVE_POPEN
  else if ( PL_is_functor(file, FUNCTOR_pipe1) )
  { term_t a;
    char *cmd;

    PL_clear_exception();
    a = PL_new_term_ref();
    _PL_get_arg(1, file, a);
    if ( !PL_get_chars(a, &cmd, CVT_ATOM|CVT_STRING|REP_FN) )
    { PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_atom, a);
      return NULL;
    }

    if ( !(s = Sopen_pipe(cmd, how)) )
    { PL_error(NULL, 0, OsError(), ERR_FILE_OPERATION,
	       ATOM_open, ATOM_source_sink, file);
      return NULL;
    }
  }
#endif /*HAVE_POPEN*/
  else
  { return NULL;
  }

  s->encoding = enc;
  if ( !close_on_abort )
    s->flags |= SIO_NOCLOSE;

  if ( how[0] == 'r' )
  { if ( eof_action != ATOM_eof_code )
    { if ( eof_action == ATOM_reset )
	s->flags |= SIO_NOFEOF;
      else if ( eof_action == ATOM_error )
	s->flags |= SIO_FEOF2ERR;
    }
  } else
  { if ( buffer != ATOM_full )
    { s->flags &= ~SIO_FBUF;
      if ( buffer == ATOM_line )
	s->flags |= SIO_LBUF;
      if ( buffer == ATOM_false )
	s->flags |= SIO_NBUF;
    }
  }

  if ( alias != NULL_ATOM )
    aliasStream(s, alias);
  if ( !reposition )
    s->position = NULL;

  if ( bom )
  { if ( mname == ATOM_read )
    { if ( ScheckBOM(s) < 0 )
      { bom_error:

	streamStatus(getStream(s));
	return NULL;
      }
    } else
    { if ( SwriteBOM(s) < 0 )
	goto bom_error;
    }
  }

  return s;
}


static
PRED_IMPL("open", 4, open4, PL_FA_ISO)
{ IOSTREAM *s = openStream(A1, A2, A4);

  if ( s )
    return PL_unify_stream_or_alias(A3, s);

  return FALSE;
}


static
PRED_IMPL("open", 3, open3, PL_FA_ISO)
{ IOSTREAM *s = openStream(A1, A2, 0);

  if ( s )
    return PL_unify_stream_or_alias(A3, s);

  return FALSE;
}

		 /*******************************
		 *	  EDINBURGH I/O		*
		 *******************************/

static IOSTREAM *
findStreamFromFile(atom_t name, unsigned int flags)
{ TableEnum e;
  Symbol symb;
  IOSTREAM *s = NULL;

  e = newTableEnum(streamContext);
  while( (symb=advanceTableEnum(e)) )
  { stream_context *ctx = symb->value;

    if ( ctx->filename == name &&
	 true(ctx, flags) )
    { s = symb->name;
      break;
    }
  }
  freeTableEnum(e);

  return s;
}


static int
pl_see(term_t f)
{ GET_LD
  IOSTREAM *s;
  atom_t a;
  term_t mode;

  LOCK();
  if ( get_stream_handle(f, &s, SH_ALIAS|SH_UNLOCKED) )
  { Scurin = s;
    goto ok;
  }

  if ( PL_get_atom(f, &a) && a == ATOM_user )
  { Scurin = Suser_input;
    goto ok;
  }
  if ( (s = findStreamFromFile(a, IO_SEE)) )
  { Scurin = s;
    goto ok;
  }

  mode = PL_new_term_ref();
  PL_put_atom(mode, ATOM_read);
  if ( !(s = openStream(f, mode, 0)) )
  { UNLOCK();
    return FALSE;
  }

  set(getStreamContext(s), IO_SEE);
  push_input_context();
  Scurin = s;

ok:
  UNLOCK();

  return TRUE;
}

static int
pl_seen(void)
{ GET_LD
  IOSTREAM *s = getStream(Scurin);

  pop_input_context();

  if ( s->flags & SIO_NOFEOF )
    return TRUE;

  return closeStream(s);
}

static
PRED_IMPL("see", 1, see, 0)
{ return pl_see(A1);
}


static
PRED_IMPL("seen", 0, seen, 0)
{ return pl_seen();
}


static
PRED_IMPL("seeing", 1, seeing, 0)
{ PRED_LD

  if ( Scurin == Suser_input )
    return PL_unify_atom(A1, ATOM_user);

  return PL_unify_stream(A1, Scurin);
}


/* MT: Does not create a lock on the stream
*/

static int
do_tell(term_t f, atom_t m)
{ GET_LD
  IOSTREAM *s;
  atom_t a;
  term_t mode;

  LOCK();
  if ( get_stream_handle(f, &s, SH_UNLOCKED) )
  { Scurout = s;
    goto ok;
  }

  if ( PL_get_atom(f, &a) && a == ATOM_user )
  { Scurout = Suser_output;
    goto ok;
  }

  if ( (s = findStreamFromFile(a, IO_TELL)) )
  { Scurout = s;
    goto ok;
  }

  mode = PL_new_term_ref();
  PL_put_atom(mode, m);
  if ( !(s = openStream(f, mode, 0)) )
  { UNLOCK();
    return FALSE;
  }

  set(getStreamContext(s), IO_TELL);
  pushOutputContext();
  Scurout = s;

ok:
  UNLOCK();
  return TRUE;
}

static
PRED_IMPL("tell", 1, tell, 0)
{ return do_tell(A1, ATOM_write);
}

static
PRED_IMPL("append", 1, append, 0)
{ return do_tell(A1, ATOM_append);
}

static
PRED_IMPL("telling", 1, telling, 0)
{ PRED_LD

  if ( Scurout == Suser_output )
    return PL_unify_atom(A1, ATOM_user);

  return PL_unify_stream(A1, Scurout);
}

static
PRED_IMPL("told", 0, told, 0)
{ PRED_LD
  IOSTREAM *s = getStream(Scurout);

  popOutputContext();

  if ( s->flags & SIO_NOFEOF )
    return TRUE;

  return closeStream(s);
}

		 /*******************************
		 *	   NULL-STREAM		*
		 *******************************/

static ssize_t
Swrite_null(void *handle, char *buf, size_t size)
{ return size;
}


static ssize_t
Sread_null(void *handle, char *buf, size_t size)
{ return 0;
}


static long
Sseek_null(void *handle, long offset, int whence)
{ switch(whence)
  { case SIO_SEEK_SET:
	return offset;
    case SIO_SEEK_CUR:
    case SIO_SEEK_END:
    default:
        return -1;
  }
}


static int
Sclose_null(void *handle)
{ return 0;
}


static const IOFUNCTIONS nullFunctions =
{ Sread_null,
  Swrite_null,
  Sseek_null,
  Sclose_null
};


static
PRED_IMPL("open_null_stream", 1, open_null_stream, 0)
{ int sflags = SIO_NBUF|SIO_RECORDPOS|SIO_OUTPUT;
  IOSTREAM *s = Snew((void *)NULL, sflags, (IOFUNCTIONS *)&nullFunctions);

  if ( s )
  { s->encoding = ENC_UTF8;
    return PL_unify_stream_or_alias(A1, s);
  }

  return FALSE;
}


static
PRED_IMPL("close", 1, close, PL_FA_ISO)
{ IOSTREAM *s;

  if ( PL_get_stream_handle(A1, &s) )
    return closeStream(s);

  return FALSE;
}

static const opt_spec close2_options[] =
{ { ATOM_force,		 OPT_BOOL },
  { NULL_ATOM,		 0 }
};


static
PRED_IMPL("close", 2, close2, PL_FA_ISO)
{ IOSTREAM *s;
  int force = FALSE;

  if ( !scan_options(A2, 0, ATOM_close_option, close2_options, &force) )
    return FALSE;

  if ( !PL_get_stream_handle(A1, &s) )
    return FALSE;
  if ( !force )
    return closeStream(s);

  if ( s == Sinput )
    Sclearerr(s);
  else if ( s == Soutput || s == Serror )
  { Sflush(s);
    Sclearerr(s);
  } else
  { Sflush(s);
    Sclose(s);
  }

  return TRUE;
}


		 /*******************************
		 *	 STREAM-PROPERTY	*
		 *******************************/

static int
stream_file_name_propery(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t name;

  if ( (name = getStreamContext(s)->filename) )
  { return PL_unify_atom(prop, name);
  }

  return FALSE;
}


static int
stream_mode_property(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t mode;

  if ( s->flags & SIO_INPUT )
    mode = ATOM_read;
  else
  { assert(s->flags & SIO_OUTPUT);

    if ( s->flags & SIO_APPEND )
      mode = ATOM_append;
    else if ( s->flags & SIO_UPDATE )
      mode = ATOM_update;
    else
      mode = ATOM_write;
  }

  return PL_unify_atom(prop, mode);
}


static int
stream_input_prop(IOSTREAM *s ARG_LD)
{ return (s->flags & SIO_INPUT) ? TRUE : FALSE;
}


static int
stream_output_prop(IOSTREAM *s ARG_LD)
{ return (s->flags & SIO_OUTPUT) ? TRUE : FALSE;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Incomplete: should be non-deterministic if the stream has multiple aliases!
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
stream_alias_prop(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t name;
  stream_context *ctx = getStreamContext(s);
  int i;

  if ( PL_get_atom(prop, &name) )
  { alias *a;

    for( a = ctx->alias_head; a; a = a->next )
    { if ( a->name == name )
	return TRUE;
    }

    if ( (i=standardStreamIndexFromName(name)) >= 0 &&
	 i < 6 &&
	 s == LD->IO.streams[i] )
      return TRUE;

    return FALSE;
  }

  if ( (i=standardStreamIndexFromStream(s)) >= 0 && i < 3 )
    return PL_unify_atom(prop, standardStreams[i]);
  if ( ctx->alias_head )
    return PL_unify_atom(prop, ctx->alias_head->name);

  return FALSE;
}


static int
stream_position_prop(IOSTREAM *s, term_t prop ARG_LD)
{ if ( s->position )
  { return PL_unify_term(prop,
			 PL_FUNCTOR, FUNCTOR_stream_position4,
			   PL_INT64, s->position->charno,
			   PL_INT, s->position->lineno,
			   PL_INT, s->position->linepos,
			   PL_INT64, s->position->byteno);
  }

  return FALSE;
}


static int
stream_end_of_stream_prop(IOSTREAM *s, term_t prop ARG_LD)
{ if ( s->flags & SIO_INPUT )
  { GET_LD
    atom_t val;

    if ( s->flags & SIO_FEOF2 )
      val = ATOM_past;
    else if ( s->flags & SIO_FEOF )
      val = ATOM_at;
    else
      val = ATOM_not;

    return PL_unify_atom(prop, val);
  }

  return FALSE;
}


static int
stream_eof_action_prop(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t val;

  if ( s->flags & SIO_NOFEOF )
    val = ATOM_reset;
  else if ( s->flags & SIO_FEOF2ERR )
    val = ATOM_error;
  else
    val = ATOM_eof_code;

  return PL_unify_atom(prop, val);
}


#ifdef HAVE_FSTAT
#include <sys/stat.h>
#endif

#if !defined(S_ISREG) && defined(S_IFREG)
#define S_ISREG(m) ((m&S_IFMT) == S_IFREG)
#endif

static int
stream_reposition_prop(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t val;

  if ( s->functions->seek )
  {
#ifdef HAVE_FSTAT
    int fd = Sfileno(s);
    struct stat buf;

    if ( fstat(fd, &buf) == 0 && S_ISREG(buf.st_mode) )
      val = ATOM_true;
    else
      val = ATOM_false;
#else
    val = ATOM_true;
#endif
  } else
    val = ATOM_false;

  return PL_unify_atom(prop, val);
}


static int
stream_close_on_abort_prop(IOSTREAM *s, term_t prop ARG_LD)
{ return PL_unify_bool_ex(prop, !(s->flags & SIO_NOCLOSE));
}


static int
stream_type_prop(IOSTREAM *s, term_t prop ARG_LD)
{ return PL_unify_atom(prop, s->flags & SIO_TEXT ? ATOM_text : ATOM_binary);
}


static int
stream_file_no_prop(IOSTREAM *s, term_t prop ARG_LD)
{ int fd;

  if ( (fd = Sfileno(s)) >= 0 )
    return PL_unify_integer(prop, fd);

  return FALSE;
}


static int
stream_tty_prop(IOSTREAM *s, term_t prop ARG_LD)
{ if ( (s->flags & SIO_ISATTY) )
    return PL_unify_bool_ex(prop, TRUE);

  return FALSE;
}


static int
stream_bom_prop(IOSTREAM *s, term_t prop ARG_LD)
{ if ( (s->flags & SIO_BOM) )
    return PL_unify_bool_ex(prop, TRUE);

  return FALSE;
}


static int
stream_newline_prop(IOSTREAM *s, term_t prop ARG_LD)
{ switch ( s->newline )
  { case SIO_NL_POSIX:
    case SIO_NL_DETECT:
      return PL_unify_atom(prop, ATOM_posix);
    case SIO_NL_DOS:
      return PL_unify_atom(prop, ATOM_dos);
  }

  return FALSE;
}


static int
stream_encoding_prop(IOSTREAM *s, term_t prop ARG_LD)
{ return PL_unify_atom(prop, encoding_to_atom(s->encoding));
}


static int
stream_reperror_prop(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t a;

  if ( (s->flags & SIO_REPXML) )
    a = ATOM_xml;
  else if ( (s->flags & SIO_REPPL) )
    a = ATOM_prolog;
  else
    a = ATOM_error;

  return PL_unify_atom(prop, a);
}


static int
stream_buffer_prop(IOSTREAM *s, term_t prop ARG_LD)
{ atom_t b;

  if ( s->flags & SIO_FBUF )
    b = ATOM_full;
  else if ( s->flags & SIO_LBUF )
    b = ATOM_line;
  else /*if ( s->flags & SIO_NBUF )*/
    b = ATOM_false;

  return PL_unify_atom(prop, b);
}


static int
stream_buffer_size_prop(IOSTREAM *s, term_t prop ARG_LD)
{ if ( (s->flags & SIO_NBUF) )
    return FALSE;

  return PL_unify_integer(prop, s->bufsize);
}


static int
stream_timeout_prop(IOSTREAM *s, term_t prop ARG_LD)
{ if ( s->timeout == -1 )
    return PL_unify_atom(prop, ATOM_infinite);

  return PL_unify_float(prop, (double)s->timeout/1000.0);
}


static int
stream_nlink_prop(IOSTREAM *s, term_t prop ARG_LD)
{ int fd;

  if ( (fd = Sfileno(s)) >= 0 )
  { struct stat buf;

    if ( fstat(fd, &buf) == 0 )
    { return PL_unify_integer(prop, buf.st_nlink);
    }
  }

  return FALSE;
}


typedef struct
{ functor_t functor;			/* functor of property */
  int (*function)();			/* function to generate */
} sprop;


static const sprop sprop_list [] =
{ { FUNCTOR_file_name1,	    stream_file_name_propery },
  { FUNCTOR_mode1,	    stream_mode_property },
  { FUNCTOR_input0,	    stream_input_prop },
  { FUNCTOR_output0,	    stream_output_prop },
  { FUNCTOR_alias1,	    stream_alias_prop },
  { FUNCTOR_position1,	    stream_position_prop },
  { FUNCTOR_end_of_stream1, stream_end_of_stream_prop },
  { FUNCTOR_eof_action1,    stream_eof_action_prop },
  { FUNCTOR_reposition1,    stream_reposition_prop },
  { FUNCTOR_type1,    	    stream_type_prop },
  { FUNCTOR_file_no1,	    stream_file_no_prop },
  { FUNCTOR_buffer1,	    stream_buffer_prop },
  { FUNCTOR_buffer_size1,   stream_buffer_size_prop },
  { FUNCTOR_close_on_abort1,stream_close_on_abort_prop },
  { FUNCTOR_tty1,	    stream_tty_prop },
  { FUNCTOR_encoding1,	    stream_encoding_prop },
  { FUNCTOR_bom1,	    stream_bom_prop },
  { FUNCTOR_newline1,	    stream_newline_prop },
  { FUNCTOR_representation_errors1, stream_reperror_prop },
  { FUNCTOR_timeout1,       stream_timeout_prop },
  { FUNCTOR_nlink1,         stream_nlink_prop },
  { 0,			    NULL }
};


typedef struct
{ TableEnum e;				/* Enumerator on stream-table */
  IOSTREAM *s;				/* Stream we are enumerating */
  const sprop *p;			/* Pointer in properties */
  int fixed_p;				/* Propety is given */
} prop_enum;


static
PRED_IMPL("stream_property", 2, stream_property,
	  PL_FA_ISO|PL_FA_NONDETERMINISTIC)
{ PRED_LD
  IOSTREAM *s;
  prop_enum *pe;
  fid_t fid;
  term_t a1;

  term_t stream = A1;
  term_t property = A2;

  switch( CTX_CNTRL )
  { case FRG_FIRST_CALL:
      a1 = PL_new_term_ref();

      if ( PL_is_variable(stream) )	/* generate */
      {	const sprop *p = sprop_list;
	int fixed = FALSE;
	functor_t f;

	if ( PL_get_functor(property, &f) ) /* test for defined property */
	{ for( ; p->functor; p++ )
	  { if ( f == p->functor )
	    { fixed = TRUE;
	      break;
	    }
	  }
	  if ( !p->functor )
	    return PL_error(NULL, 0, NULL, ERR_DOMAIN,
			    ATOM_stream_property, property);
	}

	pe = allocHeap(sizeof(*pe));

	pe->e = newTableEnum(streamContext);
	pe->s = NULL;
	pe->p = p;
	pe->fixed_p = fixed;

	break;
      }

      LOCK();				/* given stream */
      if ( get_stream_handle(stream, &s, SH_ERRORS|SH_UNLOCKED) )
      { functor_t f;

	if ( PL_is_variable(property) )	/* generate properties */
	{ pe = allocHeap(sizeof(*pe));

	  pe->e = NULL;
	  pe->s = s;
	  pe->p = sprop_list;
	  pe->fixed_p = FALSE;
	  UNLOCK();

	  break;
	}

	if ( PL_get_functor(property, &f) )
	{ const sprop *p = sprop_list;

	  for( ; p->functor; p++ )
	  { if ( f == p->functor )
	    { int rval;

	      switch(arityFunctor(f))
	      { case 0:
		  rval = (*p->function)(s PASS_LD);
		  break;
		case 1:
		{ term_t a1 = PL_new_term_ref();

		  _PL_get_arg(1, property, a1);
		  rval = (*p->function)(s, a1 PASS_LD);
		  break;
		}
		default:
		  assert(0);
		  rval = FALSE;
	      }
	      UNLOCK();
	      return rval;
	    }
	  }
	} else
	{ UNLOCK();
	  return PL_error(NULL, 0, NULL, ERR_DOMAIN,
			  ATOM_stream_property, property);
	}
      }
      UNLOCK();
      return FALSE;				/* bad stream handle */
    case FRG_REDO:
    { pe = CTX_PTR;
      a1 = PL_new_term_ref();

      break;
    }
    case FRG_CUTTED:
    { pe = CTX_PTR;

      if ( pe )				/* 0 if exception on FRG_FIRST_CALL */
      { if ( pe->e )
	  freeTableEnum(pe->e);

	freeHeap(pe, sizeof(*pe));
      }
      return TRUE;
    }
    default:
      assert(0);
      return FALSE;
  }


  if ( !(fid = PL_open_foreign_frame()) )
  { error:

    if ( pe->e )
      freeTableEnum(pe->e);

    freeHeap(pe, sizeof(*pe));
    return FALSE;
  }

  for(;;)
  { if ( pe->s )				/* given stream */
    { fid_t fid2;

      if ( PL_is_variable(stream) )
      { if ( !PL_unify_stream(stream, pe->s) )
	  goto enum_e;
      }

      if ( !(fid2 = PL_open_foreign_frame()) )
	goto error;
      for( ; pe->p->functor ; pe->p++ )
      { if ( PL_unify_functor(property, pe->p->functor) )
	{ int rval;

	  switch(arityFunctor(pe->p->functor))
	  { case 0:
	      rval = (*pe->p->function)(pe->s PASS_LD);
	      break;
	    case 1:
	    { _PL_get_arg(1, property, a1);

	      rval = (*pe->p->function)(pe->s, a1 PASS_LD);
	      break;
	    }
	    default:
	      assert(0);
	      rval = FALSE;
	  }
	  if ( rval )
	  { if ( pe->fixed_p )
	      pe->s = NULL;
	    else
	      pe->p++;
	    ForeignRedoPtr(pe);
	  }
	}

	if ( exception_term )
	  goto error;

	if ( pe->fixed_p )
	  break;
	PL_rewind_foreign_frame(fid2);
      }
      PL_close_foreign_frame(fid2);
      pe->s = NULL;
    }

  enum_e:
    if ( pe->e )
    { Symbol symb;

      while ( (symb=advanceTableEnum(pe->e)) )
      { PL_rewind_foreign_frame(fid);
	if ( PL_unify_stream(stream, symb->name) )
	{ pe->s = symb->name;
	  if ( !pe->fixed_p )
	    pe->p = sprop_list;
	  break;
	}
	if ( exception_term )
	  goto error;
      }
    }

    if ( !pe->s )
    { if ( pe->e )
	freeTableEnum(pe->e);

      freeHeap(pe, sizeof(*pe));
      return FALSE;
    }
  }
}


static
PRED_IMPL("is_stream", 1, is_stream, 0)
{ GET_LD
  IOSTREAM *s;

  if ( get_stream_handle(A1, &s, SH_SAFE) )
  { releaseStream(s);
    return TRUE;
  }

  return FALSE;
}



		 /*******************************
		 *	      FLUSH		*
		 *******************************/


static int
flush_output(term_t out)
{ IOSTREAM *s;

  if ( getOutputStream(out, &s) )
  { Sflush(s);
    return streamStatus(s);
  }

  return FALSE;
}

static
PRED_IMPL("flush_output", 0, flush_output, PL_FA_ISO)
{ return flush_output(0);
}

static
PRED_IMPL("flush_output", 1, flush_output1, PL_FA_ISO)
{ return flush_output(A1);
}


static int
getStreamWithPosition(term_t stream, IOSTREAM **sp)
{ IOSTREAM *s;

  if ( PL_get_stream_handle(stream, &s) )
  { if ( !s->position )
    { PL_error(NULL, 0, NULL, ERR_PERMISSION, /* non-ISO */
	       ATOM_property, ATOM_position, stream);
      releaseStream(s);
      return FALSE;
    }

    *sp = s;
    return TRUE;
  }

  return FALSE;
}


static int
getRepositionableStream(term_t stream, IOSTREAM **sp)
{ GET_LD
  IOSTREAM *s;

  if ( get_stream_handle(stream, &s, SH_ERRORS) )
  { if ( !s->position || !s->functions || !s->functions->seek )
    { PL_error(NULL, 0, NULL, ERR_PERMISSION,
	       ATOM_reposition, ATOM_stream, stream);
      releaseStream(s);
      return FALSE;
    }

    *sp = s;
    return TRUE;
  }

  return FALSE;
}


static
PRED_IMPL("set_stream_position", 2, set_stream_position, PL_FA_ISO)
{ PRED_LD
  IOSTREAM *s;
  int64_t charno, byteno;
  long linepos, lineno;
  term_t a = PL_new_term_ref();

  term_t stream = A1;
  term_t pos = A2;

  if ( !(getRepositionableStream(stream, &s)) )
    return FALSE;

  if ( !PL_is_functor(pos, FUNCTOR_stream_position4) ||
       !PL_get_arg(1, pos, a) ||
       !PL_get_int64(a, &charno) ||
       !PL_get_arg(2, pos, a) ||
       !PL_get_long(a, &lineno) ||
       !PL_get_arg(3, pos, a) ||
       !PL_get_long(a, &linepos) ||
       !PL_get_arg(4, pos, a) ||
       !PL_get_int64(a, &byteno) )
  { releaseStream(s);
    return PL_error("stream_position", 3, NULL,
		    ERR_DOMAIN, ATOM_stream_position, pos);
  }

  if ( Sseek64(s, byteno, SIO_SEEK_SET) != 0 )
    return PL_error(NULL, 0, MSG_ERRNO, ERR_FILE_OPERATION,
		    ATOM_reposition, ATOM_stream, stream);

  s->position->byteno  = byteno;
  s->position->charno  = charno;
  s->position->lineno  = (int)lineno;
  s->position->linepos = (int)linepos;

  releaseStream(s);

  return TRUE;
}


static
PRED_IMPL("seek", 4, seek, 0)
{ PRED_LD
  atom_t m;
  int whence = -1;
  int64_t off, new;
  IOSTREAM *s;

  term_t stream = A1;
  term_t offset = A2;
  term_t method = A3;
  term_t newloc = A4;

  if ( !(PL_get_atom_ex(method, &m)) )
    return FALSE;

  if ( m == ATOM_bof )
    whence = SIO_SEEK_SET;
  else if ( m == ATOM_current )
    whence = SIO_SEEK_CUR;
  else if ( m == ATOM_eof )
    whence = SIO_SEEK_END;
  else
    return PL_error("seek", 4, NULL, ERR_DOMAIN, ATOM_seek_method, method);

  if ( !PL_get_int64(offset, &off) )
    return PL_error("seek", 4, NULL, ERR_DOMAIN, ATOM_integer, offset);

  if ( PL_get_stream_handle(stream, &s) )
  { int unit = Sunit_size(s);

    off *= unit;
    if ( Sseek64(s, off, whence) < 0 )
    { if ( errno == EINVAL )
	PL_error("seek", 4, "offset out of range", ERR_DOMAIN,
		 ATOM_position, offset);
      else
	PL_error("seek", 4, OsError(), ERR_PERMISSION,
		 ATOM_reposition, ATOM_stream, stream);
      Sclearerr(s);
      releaseStream(s);
      return FALSE;
    }

    new = Stell64(s);
    releaseStream(s);
    new /= unit;

    return PL_unify_int64(newloc, new);
  }

  return FALSE;
}


static
PRED_IMPL("set_input", 1, set_input, PL_FA_ISO)
{ PRED_LD
  IOSTREAM *s;

  if ( getInputStream(A1, &s) )
  { Scurin = s;
    releaseStream(s);
    return TRUE;
  }

  return FALSE;
}


static
PRED_IMPL("set_output", 1, set_output, PL_FA_ISO)
{ PRED_LD
  IOSTREAM *s;

  if ( getOutputStream(A1, &s) )
  { Scurout = s;
    releaseStream(s);
    return TRUE;
  }

  return FALSE;
}


static
PRED_IMPL("current_input", 1, current_input, PL_FA_ISO)
{ PRED_LD
  return PL_unify_stream(A1, Scurin);
}


static
PRED_IMPL("current_output", 1, current_output, PL_FA_ISO)
{ PRED_LD
  return PL_unify_stream(A1, Scurout);
}


static
PRED_IMPL("byte_count", 2, byte_count, 0)
{ IOSTREAM *s;

  if ( getStreamWithPosition(A1, &s) )
  { int64_t n = s->position->byteno;

    releaseStream(s);
    return PL_unify_int64(A2, n);
  }

  return FALSE;
}


static
PRED_IMPL("character_count", 2, character_count, 0)
{ IOSTREAM *s;

  if ( getStreamWithPosition(A1, &s) )
  { int64_t n = s->position->charno;

    releaseStream(s);
    return PL_unify_int64(A2, n);
  }

  return FALSE;
}


static
PRED_IMPL("line_count", 2, line_count, 0)
{ GET_LD
  IOSTREAM *s;

  if ( getStreamWithPosition(A1, &s) )
  { intptr_t n = s->position->lineno;

    releaseStream(s);
    return PL_unify_integer(A2, n);
  }

  return FALSE;
}


static
PRED_IMPL("line_position", 2, line_position, 0)
{ GET_LD
  IOSTREAM *s;

  if ( getStreamWithPosition(A1, &s) )
  { intptr_t n = s->position->linepos;

    releaseStream(s);
    return PL_unify_integer(A2, n);
  }

  return FALSE;
}


static
PRED_IMPL("source_location", 2, source_location, 0)
{ PRED_LD
  if ( ReadingSource &&
       PL_unify_atom(A1, source_file_name) &&
       PL_unify_integer(A2, source_line_no) )
    return TRUE;

  return FALSE;
}


static int
at_end_of_stream(term_t stream ARG_LD)
{ IOSTREAM *s;

  if ( getInputStream(stream, &s) )
  { int rval = Sfeof(s);

    if ( rval < 0 )
    { PL_error(NULL, 0, "not-buffered stream", ERR_PERMISSION,
	       ATOM_end_of_stream, ATOM_stream, stream);
      rval = FALSE;
    }

    if ( rval && Sferror(s) )		/* due to error */
      return streamStatus(s);
    else
      releaseStream(s);

    return rval;
  }

  return FALSE;				/* exception */
}

static
PRED_IMPL("at_end_of_stream", 1, at_end_of_stream, PL_FA_ISO)
{ PRED_LD
  return at_end_of_stream(A1 PASS_LD);
}

static
PRED_IMPL("at_end_of_stream", 0, at_end_of_stream0, PL_FA_ISO)
{ PRED_LD
  return at_end_of_stream(0 PASS_LD);
}


static foreign_t
peek(term_t stream, term_t chr, int how ARG_LD)
{ IOSTREAM *s;
  IOPOS pos;
  int c;

  if ( !getInputStream(stream, &s) )
    return FALSE;

  pos = s->posbuf;
  if ( how == PL_BYTE )
  { c = Sgetc(s);
    if ( c != EOF )
      Sungetc(c, s);
  } else
  { c = Sgetcode(s);
    if ( c != EOF )
      Sungetcode(c, s);
  }
  s->posbuf = pos;
  if ( Sferror(s) )
    return streamStatus(s);
  releaseStream(s);

  return PL_unify_char(chr, c, how);
}


static
PRED_IMPL("peek_byte", 2, peek_byte2, 0)
{ PRED_LD
  return peek(A1, A2, PL_BYTE PASS_LD);
}


static
PRED_IMPL("peek_byte", 1, peek_byte1, 0)
{ PRED_LD
  return peek(0, A1, PL_BYTE PASS_LD);
}


static
PRED_IMPL("peek_code", 2, peek_code2, 0)
{ PRED_LD
  return peek(A1, A2, PL_CODE PASS_LD);
}


static
PRED_IMPL("peek_code", 1, peek_code1, 0)
{ PRED_LD
  return peek(0, A1, PL_CODE PASS_LD);
}


static
PRED_IMPL("peek_char", 2, peek_char2, 0)
{ PRED_LD
  return peek(A1, A2, PL_CHAR PASS_LD);
}


static
PRED_IMPL("peek_char", 1, peek_char1, 0)
{ PRED_LD
  return peek(0, A1, PL_CHAR PASS_LD);
}


		 /*******************************
		 *	    INTERACTION		*
		 *******************************/

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
set_prolog_IO(+In, +Out, +Error)

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

typedef struct wrappedIO
{ void		   *wrapped_handle;	/* original handle */
  IOFUNCTIONS      *wrapped_functions;	/* original functions */
  IOSTREAM	   *wrapped_stream;	/* stream we wrapped */
  IOFUNCTIONS       functions;		/* new function block */
} wrappedIO;


ssize_t
Sread_user(void *handle, char *buf, size_t size)
{ GET_LD
  wrappedIO *wio = handle;

  if ( LD->prompt.next && ttymode != TTY_RAW )
    PL_write_prompt(TRUE);
  else
    Sflush(Suser_output);

  size = (*wio->wrapped_functions->read)(wio->wrapped_handle, buf, size);
  if ( size == 0 )			/* end-of-file */
  { Sclearerr(Suser_input);
    LD->prompt.next = TRUE;
  } else if ( size > 0 && buf[size-1] == '\n' )
    LD->prompt.next = TRUE;

  return size;
}


static int
closeWrappedIO(void *handle)
{ wrappedIO *wio = handle;
  int rval;

  if ( wio->wrapped_functions->close )
    rval = (*wio->wrapped_functions->close)(wio->wrapped_handle);
  else
    rval = 0;

  wio->wrapped_stream->functions = wio->wrapped_functions;
  wio->wrapped_stream->handle = wio->wrapped_handle;
  PL_free(wio);

  return rval;
}


static void
wrapIO(IOSTREAM *s,
       ssize_t (*read)(void *, char *, size_t),
       ssize_t (*write)(void *, char *, size_t))
{ wrappedIO *wio = PL_malloc(sizeof(*wio));

  wio->wrapped_functions = s->functions;
  wio->wrapped_handle =	s->handle;
  wio->wrapped_stream = s;

  wio->functions = *s->functions;
  if ( read  ) wio->functions.read  = read;
  if ( write ) wio->functions.write = write;
  wio->functions.close = closeWrappedIO;

  s->functions = &wio->functions;
  s->handle = wio;
}


static
PRED_IMPL("set_prolog_IO", 3, set_prolog_IO, 0)
{ PRED_LD
  IOSTREAM *in = NULL, *out = NULL, *error = NULL;
  int rval = FALSE;
  int wrapin = FALSE;

  if ( !get_stream_handle(A1, &in, SH_ERRORS|SH_ALIAS|SH_UNLOCKED) ||
       !get_stream_handle(A2, &out, SH_ERRORS|SH_ALIAS) )
    goto out;

  wrapin = (LD->IO.streams[0] != in);
  if ( wrapin )
    in = getStream(in);			/* lock it */

  if ( PL_compare(A2, A3) == 0 )	/* == */
  { error = getStream(Snew(out->handle, out->flags, out->functions));
    error->flags &= ~SIO_ABUF;		/* disable buffering */
    error->flags |= SIO_NBUF;
  } else
  { if ( !PL_get_stream_handle(A3, &error) )
      goto out;
  }

  LOCK();
  out->flags &= ~SIO_ABUF;		/* output: line buffered */
  out->flags |= SIO_LBUF;

  LD->IO.streams[1] = out;		/* user_output */
  LD->IO.streams[2] = error;		/* user_error */
  LD->IO.streams[4] = out;		/* current_output */

  if ( wrapin )
  { LD->IO.streams[3] = in;		/* current_input */
    LD->IO.streams[0] = in;		/* user_input */
    wrapIO(in, Sread_user, NULL);
    LD->prompt.next = TRUE;
  }

  UNLOCK();
  rval = TRUE;

out:
  if ( wrapin && in )
    releaseStream(in);
  if ( out )
    releaseStream(out);
  if ( error && error != out )
    releaseStream(error);

  return rval;
}


static
PRED_IMPL("$size_stream", 2, size_stream, 0)
{ GET_LD
  IOSTREAM *s;
  int rval;

  if ( !PL_get_stream_handle(A1, &s) )
    return FALSE;

  rval = PL_unify_integer(A2, Ssize(s));
  PL_release_stream(s);

  return rval;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
copy_stream_data(+StreamIn, +StreamOut, [Len])
	Copy all data from StreamIn to StreamOut.  Should be somewhere else,
	and maybe we need something else to copy resources.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
copy_stream_data(term_t in, term_t out, term_t len ARG_LD)
{ IOSTREAM *i, *o;
  int c;
  int count = 0;

  if ( !getInputStream(in, &i) )
    return FALSE;
  if ( !getOutputStream(out, &o) )
  { releaseStream(i);
    return FALSE;
  }

  if ( !len )
  { while ( (c = Sgetcode(i)) != EOF )
    { if ( (++count % 4096) == 0 && PL_handle_signals() < 0 )
      { releaseStream(i);
	releaseStream(o);
	return FALSE;
      }
      if ( Sputcode(c, o) < 0 )
      { releaseStream(i);
	return streamStatus(o);
      }
    }
  } else
  { int64_t n;

    if ( !PL_get_int64_ex(len, &n) )
      return FALSE;

    while ( n-- > 0 && (c = Sgetcode(i)) != EOF )
    { if ( (++count % 4096) == 0 && PL_handle_signals() < 0 )
      { releaseStream(i);
	releaseStream(o);
	return FALSE;
      }
      if ( Sputcode(c, o) < 0 )
      { releaseStream(i);
	return streamStatus(o);
      }
    }
  }

  releaseStream(o);
  return streamStatus(i);
}

static
PRED_IMPL("copy_stream_data", 3, copy_stream_data3, 0)
{ PRED_LD
  return copy_stream_data(A1, A2, A3 PASS_LD);
}

static
PRED_IMPL("copy_stream_data", 2, copy_stream_data2, 0)
{ PRED_LD
  return copy_stream_data(A1, A2, 0 PASS_LD);
}


		 /*******************************
		 *      PUBLISH PREDICATES	*
		 *******************************/

BeginPredDefs(file)
					/* ISO IO */
  PRED_DEF("swi_open", 4, open4, PL_FA_ISO)
  PRED_DEF("swi_open", 3, open3, PL_FA_ISO)
  PRED_DEF("swi_close", 1, close, PL_FA_ISO)
  PRED_DEF("swi_close", 2, close2, PL_FA_ISO)
  PRED_DEF("swi_set_input", 1, set_input, PL_FA_ISO)
  PRED_DEF("swi_set_output", 1, set_output, PL_FA_ISO)
  PRED_DEF("swi_current_input", 1, current_input, PL_FA_ISO)
  PRED_DEF("swi_current_output", 1, current_output, PL_FA_ISO)
  PRED_DEF("swi_get_code", 2, get_code2, PL_FA_ISO)
  PRED_DEF("swi_get_code", 1, get_code1, PL_FA_ISO)
  PRED_DEF("swi_get_char", 2, get_char2, PL_FA_ISO)
  PRED_DEF("swi_get_char", 1, get_char1, PL_FA_ISO)
  PRED_DEF("swi_get_byte", 2, get_byte2, PL_FA_ISO)
  PRED_DEF("swi_get_byte", 1, get_byte1, PL_FA_ISO)
  PRED_DEF("swi_peek_code", 2, peek_code2, PL_FA_ISO)
  PRED_DEF("swi_peek_code", 1, peek_code1, PL_FA_ISO)
  PRED_DEF("swi_peek_char", 2, peek_char2, PL_FA_ISO)
  PRED_DEF("swi_peek_char", 1, peek_char1, PL_FA_ISO)
  PRED_DEF("swi_peek_byte", 2, peek_byte2, PL_FA_ISO)
  PRED_DEF("swi_peek_byte", 1, peek_byte1, PL_FA_ISO)
  PRED_DEF("swi_put_byte", 2, put_byte2, PL_FA_ISO)
  PRED_DEF("swi_put_byte", 1, put_byte1, PL_FA_ISO)
  PRED_DEF("swi_put_code", 2, put_code2, PL_FA_ISO)
  PRED_DEF("swi_put_code", 1, put_code1, PL_FA_ISO)
  PRED_DEF("swi_put_char", 2, put_code2, PL_FA_ISO)
  PRED_DEF("swi_put_char", 1, put_code1, PL_FA_ISO)
  PRED_DEF("swi_flush_output", 0, flush_output, PL_FA_ISO)
  PRED_DEF("swi_flush_output", 1, flush_output1, PL_FA_ISO)
  PRED_DEF("swi_at_end_of_stream", 1, at_end_of_stream, PL_FA_ISO)
  PRED_DEF("swi_at_end_of_stream", 0, at_end_of_stream0, PL_FA_ISO)
  PRED_DEF("swi_stream_property", 2, stream_property,
	   PL_FA_ISO|PL_FA_NONDETERMINISTIC)
  PRED_DEF("swi_set_stream_position", 2, set_stream_position, PL_FA_ISO)

					/* edinburgh IO */
  PRED_DEF("swi_see", 1, see, 0)
  PRED_DEF("swi_seen", 0, seen, 0)
  PRED_DEF("swi_seeing", 1, seeing, 0)
  PRED_DEF("swi_tell", 1, tell, 0)
  PRED_DEF("swi_append", 1, append, 0)
  PRED_DEF("swi_told", 0, told, 0)
  PRED_DEF("swi_telling", 1, telling, 0)
  PRED_DEF("swi_put", 2, put2, 0)
  PRED_DEF("swi_put", 1, put1, 0)
  PRED_DEF("swi_skip", 1, skip1, 0)
  PRED_DEF("swi_skip", 2, skip2, 0)
  PRED_DEF("swi_get", 1, get1, 0)
  PRED_DEF("swi_get", 2, get2, 0)
  PRED_DEF("swi_get0", 2, get_code2, 0)
  PRED_DEF("swi_get0", 1, get_code1, 0)
  PRED_DEF("swi_ttyflush", 0, ttyflush, 0)
  PRED_DEF("swi_prompt", 2, prompt, 0)
  PRED_DEF("swi_tab", 2, tab2, 0)
  PRED_DEF("swi_tab", 1, tab1, 0)
					/* Quintus IO */
  PRED_DEF("swi_byte_count", 2, byte_count, 0)
  PRED_DEF("swi_character_count", 2, character_count, 0)
  PRED_DEF("swi_line_count", 2, line_count, 0)
  PRED_DEF("swi_line_position", 2, line_position, 0)
  PRED_DEF("swi_open_null_stream", 1, open_null_stream, 0)

					/* SWI specific */
  PRED_DEF("swi_is_stream", 1, is_stream, 0)
  PRED_DEF("swi_set_stream", 2, set_stream, 0)
  PRED_DEF("swi_with_output_to", 2, with_output_to, PL_FA_TRANSPARENT)
  PRED_DEF("swi_set_prolog_IO", 3, set_prolog_IO, 0)
  PRED_DEF("swi_protocol", 1, protocol, 0)
  PRED_DEF("swi_protocola", 1, protocola, 0)
  PRED_DEF("swi_noprotocol", 0, noprotocol, 0)
  PRED_DEF("swi_protocolling", 1, protocolling, 0)
  PRED_DEF("swi_prompt1", 1, prompt1, 0)
  PRED_DEF("swi_seek", 4, seek, 0)
  PRED_DEF("swi_wait_for_input", 3, wait_for_input, 0)
  PRED_DEF("swi_get_single_char", 1, get_single_char, 0)
  PRED_DEF("swi_read_pending_input", 3, read_pending_input, 0)
  PRED_DEF("swi_source_location", 2, source_location, 0)
  PRED_DEF("swi_copy_stream_data", 3, copy_stream_data3, 0)
  PRED_DEF("swi_copy_stream_data", 2, copy_stream_data2, 0)

					/* SWI internal */
  PRED_DEF("swi_$push_input_context", 0, push_input_context, 0)
  PRED_DEF("swi_$pop_input_context", 0, pop_input_context, 0)
  PRED_DEF("swi_$size_stream", 2, size_stream, 0)
EndPredDefs

#if __YAP_PROLOG__
static void
init_yap_extras()
{
  initCharTypes();
  initFiles();
  initGlob();
  PL_register_extensions(PL_predicates_from_file);
  fileerrors = TRUE;
  SinitStreams();
}

#ifdef _WIN32

#include <windows.h>

int WINAPI PROTO(win_plstream, (HANDLE, DWORD, LPVOID));

int WINAPI win_plstream(HANDLE hinst, DWORD reason, LPVOID reserved)
{
  switch (reason) 
    {
    case DLL_PROCESS_ATTACH:
      break;
    case DLL_PROCESS_DETACH:
      break;
    case DLL_THREAD_ATTACH:
      break;
    case DLL_THREAD_DETACH:
      break;
    }
  return 1;
}
#endif
#endif