--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lstream.c	Mon Aug 13 08:45:50 2007 +0200
@@ -0,0 +1,1699 @@
+/* Generic stream implementation.
+   Copyright (C) 1995 Free Software Foundation, Inc.
+   Copyright (C) 1995 Sun Microsystems, Inc.
+   Copyright (C) 1996 Ben Wing.
+
+This file is part of XEmacs.
+
+XEmacs is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option) any
+later version.
+
+XEmacs 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 General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with XEmacs; see the file COPYING.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA.  */
+
+/* Synched up with: Not in FSF. */
+
+/* Written by Ben Wing. */
+
+#include <config.h>
+#include "lisp.h"
+
+#include "buffer.h"
+#include "insdel.h"
+#include "lstream.h"
+
+#include "sysfile.h"
+#include <errno.h>
+
+/* This function provides a generic buffering stream implementation.
+   Conceptually, you send data to the stream or read data from the
+   stream, not caring what's on the other end of the stream.  The
+   other end could be another stream, a file descriptor, a stdio
+   stream, a fixed block of memory, a reallocating block of memory,
+   etc.  The main purpose of the stream is to provide a standard
+   interface and to do buffering.  Macros are defined to read
+   or write characters, so the calling functions do not have to
+   worry about blocking data together in order to achieve efficiency.
+   */
+
+/* Note that this object is called "stream" in Lisp but "lstream"
+   in C.  The reason for this is that "stream" is too generic a name
+   for C; too much likelihood of conflict/confusion with C++, etc. */
+
+/* Functions are as follows:
+
+Lstream *Lstream_new (Lstream_implementation *imp, CONST char *mode)
+	Allocate and return a new Lstream.  This function is not
+	really meant to be called directly; rather, each stream type
+	should provide its own stream creation function, which
+	creates the stream and does any other necessary creation
+	stuff (e.g. opening a file).
+
+void Lstream_set_buffering (Lstream *lstr, Lstream_buffering buffering,
+			    int buffering_size)
+	Change the buffering of a stream.  See lstream.h.  By default
+	the buffering is STREAM_BLOCK_BUFFERED.
+
+int Lstream_flush (Lstream *lstr)
+	Flush out any pending unwritten data in the stream.  Clear
+	any buffered input data.  Returns 0 on success, -1 on error.
+
+int Lstream_putc (Lstream *stream, int c)
+	Write out one byte to the stream.  This is a macro and so
+	it is very efficient.  The C argument is only evaluated once
+	but the STREAM argument is evaluated more than once.  Returns
+	0 on success, -1 on error.
+	
+int Lstream_getc (Lstream *stream)
+	Read one byte from the stream.  This is a macro and so it
+	is very efficient.  The STREAM argument is evaluated more
+	than once.  Return value is -1 for EOF or error.
+
+void Lstream_ungetc (Lstream *stream, int c)
+	Push one byte back onto the input queue.  This will be the
+	next byte read from the stream.  Any number of bytes can be
+	pushed back and will be read in the reverse order they were
+	pushed back -- most recent first. (This is necessary for
+	consistency -- if there are a number of bytes that have been
+	unread and I read and unread a byte, it needs to be the first
+	to be read again.) This is a macro and so it is very
+	efficient.  The C argument is only evaluated once but the
+	STREAM argument is evaluated more than once.
+
+int Lstream_fputc (Lstream *stream, int c)
+int Lstream_fgetc (Lstream *stream)
+void Lstream_fungetc (Lstream *stream, int c)
+	Function equivalents of the above macros. 
+
+int Lstream_read (Lstream *stream, void *data, int size)
+	Read SIZE bytes of DATA from the stream.  Return the number of
+	bytes read.  0 means EOF. -1 means an error occurred and no
+	bytes were read.
+
+int Lstream_write (Lstream *stream, void *data, int size)
+	Write SIZE bytes of DATA to the stream.  Return the number of
+	bytes written.  -1 means an error occurred and no bytes were
+	written.
+
+void Lstream_unread (Lstream *stream, void *data, int size)
+	Push back SIZE bytes of DATA onto the input queue.  The
+	next call to Lstream_read() with the same size will read the
+	same bytes back.  Note that this will be the case even if
+	there is other pending unread data.
+
+int Lstream_close (Lstream *stream)
+	Close the stream.  All data will be flushed out.
+
+void Lstream_reopen (Lstream *stream)
+	Reopen a closed stream.  This enables I/O on it again.
+	This is not meant to be called except from a wrapper routine
+	that reinitializes variables and such -- the close routine
+	may well have freed some necessary storage structures, for
+	example.
+
+void Lstream_rewind (Lstream *stream)
+	Rewind the stream to the beginning.
+*/   
+
+MAC_DEFINE (struct lstream *, MTlstream_data)
+
+static Lisp_Object mark_lstream (Lisp_Object, void (*) (Lisp_Object));
+static void print_lstream (Lisp_Object obj, Lisp_Object printcharfun,
+			   int escapeflag);
+static void finalize_lstream (void *header, int for_disksave);
+static unsigned int sizeof_lstream (CONST void *header);
+DEFINE_LRECORD_SEQUENCE_IMPLEMENTATION ("stream", lstream,
+					mark_lstream, print_lstream,
+					finalize_lstream, 0, 0,
+					sizeof_lstream, Lstream);
+
+#define DEFAULT_BLOCK_BUFFERING_SIZE 512
+#define MAX_READ_SIZE 512
+
+static Lisp_Object
+mark_lstream (Lisp_Object obj, void (*markobj) (Lisp_Object))
+{
+  Lstream *lstr = XLSTREAM (obj);
+  if (lstr->imp->marker)
+    return (lstr->imp->marker) (obj, markobj);
+  else
+    return Qnil;
+}
+
+static void
+print_lstream (Lisp_Object obj, Lisp_Object printcharfun, int escapeflag)
+{
+  Lstream *lstr = XLSTREAM (obj);
+  char buf[200];
+
+  sprintf (buf, "#<INTERNAL EMACS BUG (%s lstream) 0x%x>",
+	   lstr->imp->name, (EMACS_INT) lstr);
+  write_c_string (buf, printcharfun);
+}
+
+static void
+finalize_lstream (void *header, int for_disksave)
+{
+  /* WARNING WARNING WARNING.  This function (and all finalize functions)
+     may get called more than once on the same object, and may get called
+     (at dump time) on objects that are not being released. */
+  Lstream *lstr = (Lstream *) header;
+
+#if 0 /* this may cause weird Broken Pipes? */
+  if (for_disksave)
+    {
+      Lstream_pseudo_close (lstr);
+      return;
+    }
+#endif
+  if (lstr->flags & LSTREAM_FL_IS_OPEN)
+    Lstream_close (lstr);
+}
+
+static unsigned int
+sizeof_lstream (CONST void *header)
+{
+  CONST Lstream *lstr = (CONST Lstream *) header;
+  return sizeof (*lstr) + lstr->imp->size - 1;
+}
+
+void
+Lstream_set_buffering (Lstream *lstr, Lstream_buffering buffering,
+		       int buffering_size)
+{
+  lstr->buffering = buffering;
+  switch (buffering)
+    {
+    case LSTREAM_UNBUFFERED:
+      lstr->buffering_size = 0; break;
+    case LSTREAM_BLOCK_BUFFERED:
+      lstr->buffering_size = DEFAULT_BLOCK_BUFFERING_SIZE; break;
+    case LSTREAM_BLOCKN_BUFFERED:
+      lstr->buffering_size = buffering_size; break;
+    case LSTREAM_LINE_BUFFERED:
+    case LSTREAM_UNLIMITED:
+      lstr->buffering_size = INT_MAX; break;
+    }
+}
+
+static CONST Lstream_implementation *lstream_types[32];
+static Lisp_Object Vlstream_free_list[32];
+static int lstream_type_count;
+
+Lstream *
+Lstream_new (CONST Lstream_implementation *imp, CONST char *mode)
+{
+  Lstream *p;
+  int i;
+
+  for (i = 0; i < lstream_type_count; i++)
+    {
+      if (lstream_types[i] == imp)
+	break;
+    }
+
+  if (i == lstream_type_count)
+    {
+      assert (lstream_type_count < countof (lstream_types));
+      lstream_types[lstream_type_count] = imp;
+      Vlstream_free_list[lstream_type_count] =
+	make_lcrecord_list (sizeof (*p) + imp->size - 1,
+			    lrecord_lstream);
+      lstream_type_count++;
+    }
+
+  p = XLSTREAM (allocate_managed_lcrecord (Vlstream_free_list[i]));
+  /* Zero it out, except the header. */
+  memset ((char *) p + sizeof (p->header), 0,
+	  sizeof (*p) - sizeof (p->header) + imp->size - 1);
+  p->imp = imp;
+  Lstream_set_buffering (p, LSTREAM_BLOCK_BUFFERED, 0);
+  p->flags = LSTREAM_FL_IS_OPEN;
+
+  /* convert mode (one of "r", "w", "rc", "wc") to p->flags */
+  assert (mode[0] == 'r' || mode[0] == 'w');
+  assert (mode[1] == 'c' || mode[1] == '\0');
+  p->flags |= (mode[0] == 'r' ? LSTREAM_FL_READ : LSTREAM_FL_WRITE);
+  if (mode[1] == 'c')
+    p->flags |= LSTREAM_FL_NO_PARTIAL_CHARS;
+
+  return p;
+}
+
+void
+Lstream_set_character_mode (Lstream *lstr)
+{
+  lstr->flags |= LSTREAM_FL_NO_PARTIAL_CHARS;
+}
+
+void
+Lstream_delete (Lstream *lstr)
+{
+  int i;
+  Lisp_Object val = Qnil;
+
+  XSETLSTREAM (val, lstr);
+  for (i = 0; i < lstream_type_count; i++)
+    {
+      if (lstream_types[i] == lstr->imp)
+	{
+	  free_managed_lcrecord (Vlstream_free_list[i], val);
+	  return;
+	}
+    }
+
+  abort ();
+}
+
+static void
+signal_simple_internal_error (CONST char *reason, Lisp_Object obj)
+{
+#ifdef DEBUG_XEMACS
+  abort ();
+#else
+  signal_simple_error (reason, obj);
+#endif
+}
+
+void
+Lstream_reopen (Lstream *lstr)
+{
+  if (lstr->flags & LSTREAM_FL_IS_OPEN)
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream already open", obj);
+    }
+  lstr->flags |= LSTREAM_FL_IS_OPEN;
+}
+
+/* Attempt to flush out all of the buffered data for writing. */
+
+int
+Lstream_flush_out (Lstream *lstr)
+{
+  int num_written;
+
+  while (lstr->out_buffer_ind > 0)
+    {
+      int size = lstr->out_buffer_ind;
+      if (! (lstr->flags & LSTREAM_FL_IS_OPEN))
+	{
+	  Lisp_Object obj = Qnil;
+	  XSETLSTREAM (obj, lstr);
+	  signal_simple_internal_error
+	    ("Internal error: lstream not open", obj);
+	}
+      if (! (lstr->flags & LSTREAM_FL_WRITE))
+	{
+	  Lisp_Object obj = Qnil;
+	  XSETLSTREAM (obj, lstr);
+	  signal_simple_internal_error
+	    ("Internal error: lstream not open for writing", obj);
+	}
+      if (!lstr->imp->writer)
+	{
+	  Lisp_Object obj = Qnil;
+	  XSETLSTREAM (obj, lstr);
+	  signal_simple_internal_error
+	    ("Internal error: lstream has no writer", obj);
+	}
+
+      if (lstr->flags & LSTREAM_FL_NO_PARTIAL_CHARS)
+	/* It's quite possible for us to get passed an incomplete
+	   character at the end.  We need to spit back that
+	   incomplete character. */
+	{
+	  CONST unsigned char *data = lstr->out_buffer;
+	  CONST unsigned char *dataend = data + size - 1;
+	  assert (size > 0); /* safety check ... */
+	  /* Optimize the most common case. */
+	  if (!BYTE_ASCII_P (*dataend))
+	    {
+	      /* Go back to the beginning of the last (and possibly partial)
+		 character, and bump forward to see if the character is
+		 complete. */
+	      VALIDATE_CHARPTR_BACKWARD (dataend);
+	      if (dataend + REP_BYTES_BY_FIRST_BYTE (*dataend) != data + size)
+		/* If not, chop the size down to ignore the last char
+		   and stash it away for next time. */
+		size = dataend - data;
+	      /* If we don't even have one character to write, then just
+		 skip out. */
+	      if (size == 0)
+		break;
+	    }
+	}
+
+      num_written =
+	(lstr->imp->writer) (lstr, lstr->out_buffer, size);
+      if (num_written == 0)
+	/* If nothing got written, then just hold the data.  This may
+	   occur, for example, if this stream does non-blocking I/O;
+	   the attempt to write the data might have resulted in an
+	   EWOULDBLOCK error. */
+	return 0;
+      else if (num_written >= lstr->out_buffer_ind)
+	lstr->out_buffer_ind = 0;
+      else if (num_written > 0)
+	{
+	  memmove (lstr->out_buffer, lstr->out_buffer + num_written,
+		   lstr->out_buffer_ind - num_written);
+	  lstr->out_buffer_ind -= num_written;
+	}
+      else
+	/* If error, just hold the data, for similar reasons as above. */
+	return -1;
+    }
+
+  if (lstr->imp->flusher)
+    return (lstr->imp->flusher) (lstr);
+
+  return 0;
+}
+
+int
+Lstream_flush (Lstream *lstr)
+{
+  if (Lstream_flush_out (lstr) < 0)
+    return -1;
+
+  /* clear out buffered data */
+  lstr->in_buffer_current = lstr->in_buffer_ind = 0;
+  lstr->unget_buffer_ind = 0;
+
+  return 0;
+}
+
+/* We want to add NUM characters.  This function ensures that the
+   buffer is large enough for this (per the buffering size specified
+   in the stream) and returns the number of characters we can
+   actually write.  If FORCE is set, ignore the buffering size
+   and go ahead and make space for all the chars even if it exceeds
+   the buffering size. (This is used to deal with the possibility
+   that the stream writer might refuse to write any bytes now, e.g.
+   if it's getting EWOULDBLOCK errors.   We have to keep stocking them
+   up until they can be written, so as to avoid losing data. */
+
+static int
+Lstream_adding (Lstream *lstr, int num, int force)
+{
+  /* Compute the size that the outbuffer needs to be after the
+     chars are added. */
+  int size_needed = max (lstr->out_buffer_size,
+			 num + lstr->out_buffer_ind);
+  /* Maybe chop it down so that we don't buffer more characters
+     than our advertised buffering size. */
+  if (!force)
+    size_needed = min (lstr->buffering_size, size_needed);
+  DO_REALLOC (lstr->out_buffer, lstr->out_buffer_size,
+	      size_needed, unsigned char);
+  /* There might be more data buffered than the buffering size,
+     so make sure we don't return a negative number here. */
+  return max (0, min (num, size_needed - lstr->out_buffer_ind));
+}
+
+/* Like Lstream_write(), but does not handle line-buffering correctly. */
+
+static int
+Lstream_write_1 (Lstream *lstr, CONST void *data, int size)
+{
+  CONST unsigned char *p = data;
+  int off = 0;
+  if (! (lstr->flags & LSTREAM_FL_IS_OPEN))
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream not open", obj);
+    }
+  if (! (lstr->flags & LSTREAM_FL_WRITE))
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream not open for writing", obj);
+    }
+  {
+    int couldnt_write_last_time = 0;
+
+    while (1)
+      {
+	/* Figure out how much we can add to the buffer */
+	int chunk = Lstream_adding (lstr, size, 0);
+	if (chunk == 0)
+	  {
+	    if (couldnt_write_last_time)
+	      /* Ung, we ran out of space and tried to flush
+		 the buffer, but it didn't work because the stream
+		 writer is refusing to accept any data.  So we
+		 just have to squirrel away all the rest of the
+		 stuff. */
+	      chunk = Lstream_adding (lstr, size, 1);
+	    else
+	      couldnt_write_last_time = 1;
+	  }
+	/* Do it. */
+	if (chunk > 0)
+          {
+            memcpy (lstr->out_buffer + lstr->out_buffer_ind, p + off, chunk);
+            lstr->out_buffer_ind += chunk;
+            lstr->byte_count     += chunk;
+            size -= chunk;
+            off  += chunk;
+          }
+	/* If the buffer is full and we have more to add, flush it out. */
+	if (size > 0)
+	  {
+	    if (Lstream_flush_out (lstr) < 0)
+	      {
+		if (off == 0)
+		  return -1;
+		else
+		  return off;
+	      }
+	  }
+	else
+	  break;
+      }
+  }
+  return off;
+}
+
+/* If the stream is not line-buffered, then we can just call
+   Lstream_write_1(), which writes in chunks.  Otherwise, we
+   repeatedly call Lstream_putc(), which knows how to handle
+   line buffering. */
+
+int
+Lstream_write (Lstream *lstr, CONST void *data, int size)
+{
+  int i;
+  CONST unsigned char *p = data;
+
+  assert (size >= 0);
+  if (size == 0)
+    return size;
+  if (lstr->buffering != LSTREAM_LINE_BUFFERED)
+    return Lstream_write_1 (lstr, data, size);
+  for (i = 0; i < size; i++)
+    {
+      if (Lstream_putc (lstr, p[i]) < 0)
+	break;
+    }
+  return i == 0 ? -1 : 0;
+}
+
+static int
+Lstream_raw_read (Lstream *lstr, unsigned char *buffer, int size)
+{
+  if (! (lstr->flags & LSTREAM_FL_IS_OPEN))
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream not open", obj);
+    }
+  if (! (lstr->flags & LSTREAM_FL_READ))
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream not open for reading", obj);
+    }
+  if (!lstr->imp->reader)
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream has no reader", obj);
+    }
+  
+  return (lstr->imp->reader) (lstr, buffer, size);
+}
+
+/* Assuming the buffer is empty, fill it up again. */
+
+static int
+Lstream_read_more (Lstream *lstr)
+{
+#if 0
+  int size_needed = max (1, min (MAX_READ_SIZE, lstr->buffering_size));
+#else
+  /* If someone requested a larger buffer size, so be it! */
+  int size_needed = max (1, lstr->buffering_size);
+#endif
+  int size_gotten;
+
+  DO_REALLOC (lstr->in_buffer, lstr->in_buffer_size,
+	      size_needed, unsigned char);
+  size_gotten = Lstream_raw_read (lstr, lstr->in_buffer, size_needed);
+  lstr->in_buffer_current = max (0, size_gotten);
+  lstr->in_buffer_ind = 0;
+  return size_gotten < 0 ? -1 : size_gotten;
+}  
+
+int
+Lstream_read (Lstream *lstr, void *data, int size)
+{
+  unsigned char *p = (unsigned char *) data;
+  int off = 0;
+  int chunk;
+  int error_occurred = 0;
+
+  assert (size >= 0);
+  if (size == 0)
+    return 0;
+
+  /* First try to get some data from the unget buffer */
+  chunk = min (size, lstr->unget_buffer_ind);
+  if (chunk > 0)
+    {
+      /* The bytes come back in reverse order. */
+      for (; off < chunk; off++)
+	p[off] = lstr->unget_buffer[--lstr->unget_buffer_ind];
+      lstr->byte_count += chunk;
+      size -= chunk;
+    }
+
+  while (size > 0)
+    {
+      /* Take whatever we can from the in buffer */
+      chunk = min (size, lstr->in_buffer_current - lstr->in_buffer_ind);
+      if (chunk > 0)
+        {
+          memcpy (p + off, lstr->in_buffer + lstr->in_buffer_ind, chunk);
+          lstr->in_buffer_ind += chunk;
+          lstr->byte_count    += chunk;
+          size -= chunk;
+          off  += chunk;
+        }
+
+      /* If we need some more, try to get some more from the stream's end */
+      if (size > 0)
+	{
+	  int retval = Lstream_read_more (lstr);
+	  if (retval < 0)
+	    error_occurred = 1;
+	  if (retval <= 0)
+	    break;
+	}
+    }
+
+  /* #### Beware of OFF ending up 0. */
+  if ((lstr->flags & LSTREAM_FL_NO_PARTIAL_CHARS) && off > 0)
+    {
+      /* It's quite possible for us to get passed an incomplete
+	 character at the end.  We need to spit back that
+	 incomplete character. */
+      CONST unsigned char *dataend = p + off - 1;
+      /* Optimize the most common case. */
+      if (!BYTE_ASCII_P (*dataend))
+	{
+	  /* Go back to the beginning of the last (and possibly partial)
+	     character, and bump forward to see if the character is
+	     complete. */
+	  VALIDATE_CHARPTR_BACKWARD (dataend);
+	  if (dataend + REP_BYTES_BY_FIRST_BYTE (*dataend) != p + off)
+	    {
+	      int newoff = dataend - p;
+	      /* If not, chop the size down to ignore the last char
+		 and stash it away for next time. */
+	      Lstream_unread (lstr, dataend, off - newoff);
+	      off = newoff;
+	    }
+	}
+    }
+
+  return ((off == 0 && error_occurred) ? -1 : off);
+}
+
+void
+Lstream_unread (Lstream *lstr, CONST void *data, int size)
+{
+  int i;
+  unsigned char *p = (unsigned char *) data;
+
+  /* Make sure buffer is big enough */
+
+  DO_REALLOC (lstr->unget_buffer, lstr->unget_buffer_size,
+	      lstr->unget_buffer_ind + size, unsigned char);
+
+  /* Bytes have to go on in reverse order -- they are reversed
+     again when read back. */
+  for (i = size - 1; i >= 0; i--)
+    lstr->unget_buffer[lstr->unget_buffer_ind++] = p[i];
+  lstr->byte_count -= size;
+}
+
+int
+Lstream_rewind (Lstream *lstr)
+{
+  if (!lstr->imp->rewinder)
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream has no rewinder", obj);
+    }
+  if (Lstream_flush (lstr) < 0)
+    return -1;
+  lstr->byte_count = 0;
+  return (lstr->imp->rewinder) (lstr);
+}
+  
+int
+Lstream_seekable_p (Lstream *lstr)
+{
+  if (!lstr->imp->rewinder)
+    return 0;
+  if (!lstr->imp->seekable_p)
+    return 1;
+  return (lstr->imp->seekable_p) (lstr);
+}
+
+static int
+Lstream_pseudo_close (Lstream *lstr)
+{
+  if (!lstr->flags & LSTREAM_FL_IS_OPEN)
+    {
+      Lisp_Object obj = Qnil;
+      XSETLSTREAM (obj, lstr);
+      signal_simple_internal_error
+	("Internal error: lstream is not open", obj);
+    }
+
+  /* don't check errors here -- best not to risk file descriptor loss */
+  Lstream_flush (lstr);
+
+  return 0;
+}
+
+int
+Lstream_close (Lstream *lstr)
+{
+  if (lstr->flags & LSTREAM_FL_IS_OPEN)
+    {
+      /* don't return here on error, or file descriptor leak will result. */
+      Lstream_pseudo_close (lstr);
+      if (lstr->imp->closer)
+	{
+	  if ((lstr->imp->closer) (lstr) < 0)
+	    return -1;
+	}
+    }
+
+  lstr->flags &= ~LSTREAM_FL_IS_OPEN;
+  lstr->byte_count = 0;
+  /* Note that Lstream_flush() reset all the buffer indices.  That way,
+     the next call to Lstream_putc(), Lstream_getc(), or Lstream_ungetc()
+     on a closed stream will call into the function equivalents, which will
+     cause an error. */
+
+  /* We set the pointers to 0 so that we don't lose when this function
+     is called more than once on the same object */
+  if (lstr->out_buffer)
+    {
+      xfree (lstr->out_buffer);
+      lstr->out_buffer = 0;
+    }
+  if (lstr->in_buffer)
+    {
+      xfree (lstr->in_buffer);
+      lstr->in_buffer = 0;
+    }
+  if (lstr->unget_buffer)
+    {
+      xfree (lstr->unget_buffer);
+      lstr->unget_buffer = 0;
+    }
+
+  return 0;
+}
+
+int
+Lstream_fputc (Lstream *lstr, int c)
+{
+  unsigned char ch = (unsigned char) c;
+  int retval = Lstream_write_1 (lstr, &ch, 1);
+  if (retval >= 0 && lstr->buffering == LSTREAM_LINE_BUFFERED && ch == '\n')
+    return Lstream_flush_out (lstr);
+  return retval < 0 ? -1 : 0;
+}
+
+int
+Lstream_fgetc (Lstream *lstr)
+{
+  unsigned char ch;
+  if (Lstream_read (lstr, &ch, 1) <= 0)
+    return -1;
+  return ch;
+}
+
+void
+Lstream_fungetc (Lstream *lstr, int c)
+{
+  unsigned char ch = (unsigned char) c;
+  Lstream_unread (lstr, &ch, 1);
+}
+
+
+/************************ some stream implementations *********************/
+
+/*********** a stdio stream ***********/
+
+struct stdio_stream
+{
+  FILE *file;
+  int closing;
+};
+
+#define STDIO_STREAM_DATA(stream) LSTREAM_TYPE_DATA (stream, stdio)
+
+DEFINE_LSTREAM_IMPLEMENTATION ("stdio", lstream_stdio,
+			       sizeof (struct stdio_stream));
+
+static Lisp_Object
+make_stdio_stream_1 (FILE *stream, int flags, CONST char *mode)
+{
+  Lisp_Object obj = Qnil;
+  Lstream *lstr = Lstream_new (lstream_stdio, mode);
+  struct stdio_stream *str = STDIO_STREAM_DATA (lstr);
+  str->file = stream;
+  str->closing = flags & LSTR_CLOSING;
+  XSETLSTREAM (obj, lstr);
+  return obj;
+}
+
+Lisp_Object
+make_stdio_input_stream (FILE *stream, int flags)
+{
+  return make_stdio_stream_1 (stream, flags, "r");
+}
+
+Lisp_Object
+make_stdio_output_stream (FILE *stream, int flags)
+{
+  return make_stdio_stream_1 (stream, flags, "w");
+}
+
+static int
+stdio_reader (Lstream *stream, unsigned char *data, int size)
+{
+  struct stdio_stream *str = STDIO_STREAM_DATA (stream);
+  size_t val = fread (data, 1, (size_t) size, str->file);
+  if (!val && ferror (str->file))
+    return -1;
+  return (int) val;
+}
+
+static int
+stdio_writer (Lstream *stream, CONST unsigned char *data, int size)
+{
+  struct stdio_stream *str = STDIO_STREAM_DATA (stream);
+  size_t val = fwrite (data, 1, (size_t) size, str->file);
+  if (!val && ferror (str->file))
+    return -1;
+  return (int) val;
+}
+
+static int
+stdio_rewinder (Lstream *stream)
+{
+  rewind (STDIO_STREAM_DATA (stream)->file);
+  return 0;
+}
+
+static int
+stdio_seekable_p (Lstream *stream)
+{
+  struct stdio_stream *str = STDIO_STREAM_DATA (stream);
+  {
+    struct stat lestat;
+
+    if (fstat (fileno (str->file), &lestat) < 0)
+      return 0;
+    return S_ISREG (lestat.st_mode);
+  }
+}
+
+static int
+stdio_flusher (Lstream *stream)
+{
+  struct stdio_stream *str = STDIO_STREAM_DATA (stream);
+  if (stream->flags & LSTREAM_FL_WRITE)
+    return fflush (str->file);
+  else
+    /* call fpurge?  Only exists on some systems. */
+    return 0;
+}
+
+static int
+stdio_closer (Lstream *stream)
+{
+  struct stdio_stream *str = STDIO_STREAM_DATA (stream);
+  if (str->closing)
+    return fclose (str->file);
+  else
+  if (stream->flags & LSTREAM_FL_WRITE)
+    return fflush (str->file);
+  else
+    /* call fpurge?  Only exists on some systems. */
+    return 0;
+}
+
+/*********** a file descriptor ***********/
+
+struct filedesc_stream
+{
+  int fd;
+  int pty_max_bytes;
+  Bufbyte eof_char;
+  int starting_pos;
+  int current_pos;
+  int end_pos;
+  int chars_sans_newline;
+  int closing :1;
+  int allow_quit :1;
+  int blocked_ok :1;
+  int pty_flushing :1;
+  int blocking_error_p :1;
+};
+
+#define FILEDESC_STREAM_DATA(stream) LSTREAM_TYPE_DATA (stream, filedesc)
+
+DEFINE_LSTREAM_IMPLEMENTATION ("filedesc", lstream_filedesc,
+			       sizeof (struct filedesc_stream));
+
+/* Make a stream that reads from or writes to a file descriptor FILEDESC.
+   OFFSET is the offset from the *current* file pointer that the reading
+   should start at.  COUNT is the number of bytes to be read (it is
+   ignored when writing); -1 for unlimited. */
+static Lisp_Object
+make_filedesc_stream_1 (int filedesc, int offset, int count, int flags,
+			CONST char *mode)
+{
+  Lisp_Object obj = Qnil;
+  Lstream *lstr = Lstream_new (lstream_filedesc, mode);
+  struct filedesc_stream *fstr = FILEDESC_STREAM_DATA (lstr);
+  fstr->fd = filedesc;
+  fstr->closing = !!(flags & LSTR_CLOSING);
+  fstr->allow_quit = !!(flags & LSTR_ALLOW_QUIT);
+  fstr->blocked_ok = !!(flags & LSTR_BLOCKED_OK);
+  fstr->pty_flushing = !!(flags & LSTR_PTY_FLUSHING);
+  fstr->blocking_error_p = 0;
+  fstr->chars_sans_newline = 0;
+  fstr->starting_pos = lseek (filedesc, offset, SEEK_CUR);
+  if (fstr->starting_pos < 0)
+    fstr->current_pos = 0;
+  else
+    fstr->current_pos = fstr->starting_pos;
+  if (count < 0)
+    fstr->end_pos = -1;
+  else
+    fstr->end_pos = fstr->starting_pos + count;
+  XSETLSTREAM (obj, lstr);
+  return obj;
+}
+
+Lisp_Object
+make_filedesc_input_stream (int filedesc, int offset, int count, int flags)
+{
+  return make_filedesc_stream_1 (filedesc, offset, count, flags, "r");
+}
+
+Lisp_Object
+make_filedesc_output_stream (int filedesc, int offset, int count, int flags)
+{
+  return make_filedesc_stream_1 (filedesc, offset, count, flags, "w");
+}
+
+static int
+filedesc_reader (Lstream *stream, unsigned char *data, int size)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  if (str->end_pos >= 0)
+    size = min (size, str->end_pos - str->current_pos);
+  size = (str->allow_quit ? read_allowing_quit : read) (str->fd, data, size);
+  if (size > 0)
+    str->current_pos += size;
+  return size;
+}
+
+static int
+errno_would_block_p (int val)
+{
+#ifdef EWOULDBLOCK
+  if (val == EWOULDBLOCK)
+    return 1;
+#endif
+#ifdef EAGAIN
+  if (val == EAGAIN)
+    return 1;
+#endif
+  return 0;
+}
+
+static int
+filedesc_writer (Lstream *stream, CONST unsigned char *data, int size)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  int retval;
+  int need_newline = 0; 
+
+  /* This function would be simple if it were not for the blasted
+     PTY max-bytes stuff.  Why the hell can't they just have written
+     the PTY drivers right so this problem doesn't exist?
+
+     Maybe all the PTY crap here should be moved into another stream
+     that does nothing but periodically insert EOF's as necessary. */
+  if (str->pty_flushing)
+    {
+      /* To make life easy, only send out one line at the most. */
+      CONST unsigned char *ptr;
+
+      ptr = memchr (data, '\n', size);
+      if (ptr)
+	need_newline = 1;
+      else
+	ptr = data + size;
+      if (ptr - data >= str->pty_max_bytes - str->chars_sans_newline)
+	{
+	  ptr = data + str->pty_max_bytes - str->chars_sans_newline;
+	  need_newline = 0;
+	}
+      size = ptr - data;
+    }
+
+  /**** start of non-PTY-crap ****/
+  if (size > 0)
+    retval = ((str->allow_quit ? write_allowing_quit : write)
+	      (str->fd, data, size));
+  else
+    retval = 0;
+  if (retval < 0 && errno_would_block_p (errno) && str->blocked_ok)
+    {
+      str->blocking_error_p = 1;
+      return 0;
+    }
+  str->blocking_error_p = 0;
+  if (retval < 0)
+    return retval;
+  /**** end non-PTY-crap ****/
+
+  if (str->pty_flushing)
+    {
+      str->chars_sans_newline += retval;
+      /* Note that a newline was not among the bytes written out.
+	 Add to the number of non-newline bytes written out,
+	 and flush with an EOF if necessary.  Be careful to
+	 keep track of write errors as we go along and look
+	 out for EWOULDBLOCK. */
+      if (str->chars_sans_newline >= str->pty_max_bytes)
+	{
+	  int retval2 = ((str->allow_quit ? write_allowing_quit : write)
+			 (str->fd, &str->eof_char, 1));
+	  if (retval2 > 0)
+	    str->chars_sans_newline = 0;
+	  else if (retval2 < 0)
+	    {
+	      /* Error writing the EOF char.  If nothing got written,
+		 then treat this as an error -- either return an error
+		 condition or set the blocking-error flag. */
+	      if (retval == 0)
+		{
+		  if (errno_would_block_p (errno) && str->blocked_ok)
+		    {
+		      str->blocking_error_p = 1;
+		      return 0;
+		    }
+		  else
+		    return retval2;
+		}
+	      else
+		return retval;
+	    }
+	}
+    }
+
+  /* The need_newline flag is necessary because otherwise when the
+     first byte is a newline, we'd get stuck never writing anything
+     in pty-flushing mode. */
+  if (need_newline)
+    {
+      Bufbyte nl = '\n';
+      int retval2 = ((str->allow_quit ? write_allowing_quit : write)
+		     (str->fd, &nl, 1));
+      if (retval2 > 0)
+        {
+          str->chars_sans_newline = 0;
+          retval++;
+        }
+      else if (retval2 < 0)
+	{
+	  /* Error writing the newline char.  If nothing got written,
+	     then treat this as an error -- either return an error
+	     condition or set the blocking-error flag. */
+	  if (retval == 0)
+	    {
+	      if (errno_would_block_p (errno) && str->blocked_ok)
+		{
+		  str->blocking_error_p = 1;
+		  return 0;
+		}
+	      else
+		return retval2;
+	    }
+	  else
+	    return retval;
+	}
+    }
+
+  return retval;
+}
+
+static int
+filedesc_rewinder (Lstream *stream)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  if (str->starting_pos < 0 ||
+      lseek (FILEDESC_STREAM_DATA (stream)->fd, str->starting_pos,
+	     SEEK_SET) == -1)
+    return -1;
+  else
+    {
+      str->current_pos = str->starting_pos;
+      return 0;
+    }
+}
+
+static int
+filedesc_seekable_p (Lstream *stream)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  if (str->starting_pos < 0)
+    return 0;
+  else
+    {
+      struct stat lestat;
+
+      if (fstat (str->fd, &lestat) < 0)
+        return 0;
+      return S_ISREG (lestat.st_mode);
+    }
+}
+
+static int
+filedesc_closer (Lstream *stream)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  if (str->closing)
+    return close (str->fd);
+  else
+    return 0;
+}
+
+void
+filedesc_stream_set_pty_flushing (Lstream *stream, int pty_max_bytes,
+				  Bufbyte eof_char)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  str->pty_max_bytes = pty_max_bytes;
+  str->eof_char = eof_char;
+}
+
+int
+filedesc_stream_was_blocked (Lstream *stream)
+{
+  struct filedesc_stream *str = FILEDESC_STREAM_DATA (stream);
+  return str->blocking_error_p;
+}
+
+/*********** read from a Lisp string ***********/
+
+#define LISP_STRING_STREAM_DATA(stream) LSTREAM_TYPE_DATA (stream, lisp_string)
+
+struct lisp_string_stream
+{
+  Lisp_Object obj;
+  Bytecount init_offset;
+  Bytecount offset, end;
+};
+
+DEFINE_LSTREAM_IMPLEMENTATION ("lisp-string", lstream_lisp_string,
+			       sizeof (struct lisp_string_stream));
+
+Lisp_Object
+make_lisp_string_input_stream (Lisp_Object string, Bytecount offset,
+			       Bytecount len)
+{
+  Lisp_Object obj = Qnil;
+  Lstream *lstr;
+  struct lisp_string_stream *str;
+
+  CHECK_STRING (string);
+  if (len < 0)
+    len = string_length (XSTRING (string)) - offset;
+  assert (offset >= 0);
+  assert (len >= 0);
+  assert (offset + len <= string_length (XSTRING (string)));
+
+  lstr = Lstream_new (lstream_lisp_string, "r");
+  str = LISP_STRING_STREAM_DATA (lstr);
+  str->offset = offset;
+  str->end = offset + len;
+  str->init_offset = offset;
+  str->obj = string;
+  XSETLSTREAM (obj, lstr);
+  return obj;
+}
+			      
+static int
+lisp_string_reader (Lstream *stream, unsigned char *data, int size)
+{
+  struct lisp_string_stream *str = LISP_STRING_STREAM_DATA (stream);
+  /* Don't lose if the string shrank past us ... */
+  Bytecount offset = min (str->offset, string_length (XSTRING (str->obj)));
+  Bufbyte *strstart = string_data (XSTRING (str->obj));
+  Bufbyte *start = strstart + offset;
+
+  /* ... or if someone changed the string and we ended up in the
+     middle of a character. */
+  /* Being in the middle of a character is `normal' unless
+     LSTREAM_NO_PARTIAL_CHARS - mrb */
+  if (stream->flags & LSTREAM_FL_NO_PARTIAL_CHARS)
+    VALIDATE_CHARPTR_BACKWARD (start);
+  offset = start - strstart;
+  size = min (size, str->end - offset);
+  assert (size >= 0); /* paranoia */
+  memcpy (data, start, size);
+  str->offset = offset + size;
+  return size;
+}
+
+static int
+lisp_string_rewinder (Lstream *stream)
+{
+  struct lisp_string_stream *str = LISP_STRING_STREAM_DATA (stream);
+  int pos = str->init_offset;
+  if (pos > str->end)
+    pos = str->end;
+  /* Don't lose if the string shrank past us ... */
+  pos = min (pos, string_length (XSTRING (str->obj)));
+  /* ... or if someone changed the string and we ended up in the
+     middle of a character. */
+  {
+    Bufbyte *strstart = string_data (XSTRING (str->obj));
+    Bufbyte *start = strstart + pos;
+    VALIDATE_CHARPTR_BACKWARD (start);
+    pos = start - strstart;
+  }
+  str->offset = pos;
+  return 0;
+}
+
+static Lisp_Object
+lisp_string_marker (Lisp_Object stream, void (*markobj) (Lisp_Object))
+{
+  struct lisp_string_stream *str = LISP_STRING_STREAM_DATA (XLSTREAM (stream));
+  return str->obj;
+}
+
+/*********** a fixed buffer ***********/
+
+#define FIXED_BUFFER_STREAM_DATA(stream) \
+  LSTREAM_TYPE_DATA (stream, fixed_buffer)
+
+struct fixed_buffer_stream
+{
+  CONST unsigned char *inbuf;
+  unsigned char *outbuf;
+  int size;
+  int offset;
+};
+
+DEFINE_LSTREAM_IMPLEMENTATION ("fixed-buffer", lstream_fixed_buffer,
+			       sizeof (struct fixed_buffer_stream));
+
+Lisp_Object
+make_fixed_buffer_input_stream (CONST unsigned char *buf, int size)
+{
+  Lisp_Object obj = Qnil;
+  Lstream *lstr;
+  struct fixed_buffer_stream *str;
+
+  lstr = Lstream_new (lstream_fixed_buffer, "r");
+  str = FIXED_BUFFER_STREAM_DATA (lstr);
+  str->inbuf = buf;
+  str->size = size;
+  XSETLSTREAM (obj, lstr);
+  return obj;
+}
+			      
+Lisp_Object
+make_fixed_buffer_output_stream (unsigned char *buf, int size)
+{
+  Lisp_Object obj = Qnil;
+  Lstream *lstr;
+  struct fixed_buffer_stream *str;
+
+  lstr = Lstream_new (lstream_fixed_buffer, "w");
+  str = FIXED_BUFFER_STREAM_DATA (lstr);
+  str->outbuf = buf;
+  str->size = size;
+  XSETLSTREAM (obj, lstr);
+  return obj;
+}
+
+static int
+fixed_buffer_reader (Lstream *stream, unsigned char *data, int size)
+{
+  struct fixed_buffer_stream *str = FIXED_BUFFER_STREAM_DATA (stream);
+  size = min (size, str->size - str->offset);
+  memcpy (data, str->inbuf + str->offset, size);
+  str->offset += size;
+  return size;
+}
+
+static int
+fixed_buffer_writer (Lstream *stream, CONST unsigned char *data, int size)
+{
+  struct fixed_buffer_stream *str = FIXED_BUFFER_STREAM_DATA (stream);
+  if (str->offset == str->size)
+    {
+      /* If we're at the end, just throw away the data and pretend
+	 we wrote all of it.  If we return 0, then the lstream routines
+	 will try again and again to write it out. */
+      return size;
+    }
+  size = min (size, str->size - str->offset);
+  memcpy (str->outbuf + str->offset, data, size);
+  str->offset += size;
+  return size;
+}
+
+static int
+fixed_buffer_rewinder (Lstream *stream)
+{
+  FIXED_BUFFER_STREAM_DATA (stream)->offset = 0;
+  return 0;
+}
+
+CONST unsigned char *
+fixed_buffer_input_stream_ptr (Lstream *stream)
+{
+  assert (stream->imp == lstream_fixed_buffer);
+  return FIXED_BUFFER_STREAM_DATA (stream)->inbuf;
+}
+
+unsigned char *
+fixed_buffer_output_stream_ptr (Lstream *stream)
+{
+  assert (stream->imp == lstream_fixed_buffer);
+  return FIXED_BUFFER_STREAM_DATA (stream)->outbuf;
+}
+
+/*********** write to a resizing buffer ***********/
+
+#define RESIZING_BUFFER_STREAM_DATA(stream) \
+  LSTREAM_TYPE_DATA (stream, resizing_buffer)
+
+struct resizing_buffer_stream
+{
+  unsigned char *buf;
+  int allocked;
+  int max_stored;
+  int stored;
+};
+
+DEFINE_LSTREAM_IMPLEMENTATION ("resizing-buffer", lstream_resizing_buffer,
+			       sizeof (struct resizing_buffer_stream));
+
+Lisp_Object
+make_resizing_buffer_output_stream (void)
+{
+  Lisp_Object obj = Qnil;
+  XSETLSTREAM (obj, Lstream_new (lstream_resizing_buffer, "w"));
+  return obj;
+}
+			      
+static int
+resizing_buffer_writer (Lstream *stream, CONST unsigned char *data, int size)
+{
+  struct resizing_buffer_stream *str = RESIZING_BUFFER_STREAM_DATA (stream);
+  DO_REALLOC (str->buf, str->allocked, str->stored + size, unsigned char);
+  memcpy (str->buf + str->stored, data, size);
+  str->stored += size;
+  str->max_stored = max (str->max_stored, str->stored);
+  return size;
+}
+
+static int
+resizing_buffer_rewinder (Lstream *stream)
+{
+  RESIZING_BUFFER_STREAM_DATA (stream)->stored = 0;
+  return 0;
+}
+
+static int
+resizing_buffer_closer (Lstream *stream)
+{
+  struct resizing_buffer_stream *str = RESIZING_BUFFER_STREAM_DATA (stream);
+  if (str->buf)
+    {
+      xfree (str->buf);
+      str->buf = 0;
+    }
+  return 0;
+}
+
+unsigned char *
+resizing_buffer_stream_ptr (Lstream *stream)
+{
+  return RESIZING_BUFFER_STREAM_DATA (stream)->buf;
+}
+
+/*********** write to an unsigned-char dynarr ***********/
+
+/* Note: If you have a dynarr whose type is not unsigned_char_dynarr
+   but which is really just an unsigned_char_dynarr (e.g. its type
+   is Bufbyte or Extbyte), just cast to unsigned_char_dynarr. */
+
+#define DYNARR_STREAM_DATA(stream) \
+  LSTREAM_TYPE_DATA (stream, dynarr)
+
+struct dynarr_stream
+{
+  unsigned_char_dynarr *dyn;
+};
+
+DEFINE_LSTREAM_IMPLEMENTATION ("dynarr", lstream_dynarr,
+			       sizeof (struct dynarr_stream));
+
+Lisp_Object
+make_dynarr_output_stream (unsigned_char_dynarr *dyn)
+{
+  Lisp_Object obj = Qnil;
+  XSETLSTREAM (obj, Lstream_new (lstream_dynarr, "w"));
+  DYNARR_STREAM_DATA (XLSTREAM (obj))->dyn = dyn;
+  return obj;
+}
+			      
+static int
+dynarr_writer (Lstream *stream, CONST unsigned char *data, int size)
+{
+  struct dynarr_stream *str = DYNARR_STREAM_DATA (stream);
+  Dynarr_add_many (str->dyn, data, size);
+  return size;
+}
+
+static int
+dynarr_rewinder (Lstream *stream)
+{
+  Dynarr_reset (DYNARR_STREAM_DATA (stream)->dyn);
+  return 0;
+}
+
+static int
+dynarr_closer (Lstream *stream)
+{
+  return 0;
+}
+
+/************ read from or write to a Lisp buffer ************/
+
+/* Note: Lisp-buffer read streams never return partial characters,
+   and Lisp-buffer write streams expect to never get partial
+   characters. */
+
+#define LISP_BUFFER_STREAM_DATA(stream) \
+  LSTREAM_TYPE_DATA (stream, lisp_buffer)
+
+struct lisp_buffer_stream
+{
+  Lisp_Object buffer;
+  Lisp_Object orig_start;
+  /* we use markers to properly deal with insertion/deletion */
+  Lisp_Object start, end;
+  int flags;
+};
+
+DEFINE_LSTREAM_IMPLEMENTATION ("lisp-buffer", lstream_lisp_buffer,
+			       sizeof (struct lisp_buffer_stream));
+
+static Lisp_Object
+make_lisp_buffer_stream_1 (struct buffer *buf, Bufpos start, Bufpos end,
+			   int flags, CONST char *mode)
+{
+  Lisp_Object obj = Qnil;
+  Lstream *lstr;
+  struct lisp_buffer_stream *str;
+  Bufpos bmin, bmax;
+  int reading = !strcmp (mode, "r");
+
+  /* Make sure the luser didn't pass "w" in. */
+  if (!strcmp (mode, "w"))
+    abort ();
+  
+  if (flags & LSTR_IGNORE_ACCESSIBLE)
+    {
+      bmin = BUF_BEG (buf);
+      bmax = BUF_Z (buf);
+    }
+  else
+    {
+      bmin = BUF_BEGV (buf);
+      bmax = BUF_ZV (buf);
+    }
+
+  if (start == -1)
+    start = bmin;
+  if (end == -1)
+    end = bmax;
+  assert (bmin <= start);
+  assert (start <= bmax);
+  if (reading)
+    {
+      assert (bmin  <= end);
+      assert (end   <= bmax);
+      assert (start <= end);
+    }
+
+  lstr = Lstream_new (lstream_lisp_buffer, mode);
+  str = LISP_BUFFER_STREAM_DATA (lstr);
+  {
+    Lisp_Object marker;
+    Lisp_Object buffer = Qnil;
+
+    XSETBUFFER (buffer, buf);
+    marker = Fmake_marker ();
+    Fset_marker (marker, make_int (start), buffer);
+    str->start = marker;
+    marker = Fmake_marker ();
+    Fset_marker (marker, make_int (start), buffer);
+    str->orig_start = marker;
+    if (reading)
+      {
+        marker = Fmake_marker ();
+        Fset_marker (marker, make_int (end), buffer);
+        str->end = marker;
+      }
+    else
+      str->end = Qnil;
+    str->buffer = buffer;
+  }
+  str->flags = flags;
+  XSETLSTREAM (obj, lstr);
+  return obj;
+}
+
+Lisp_Object
+make_lisp_buffer_input_stream (struct buffer *buf, Bufpos start, Bufpos end,
+			       int flags)
+{
+  return make_lisp_buffer_stream_1 (buf, start, end, flags, "r");
+}
+
+Lisp_Object
+make_lisp_buffer_output_stream (struct buffer *buf, Bufpos pos, int flags)
+{
+  Lisp_Object lstr = make_lisp_buffer_stream_1 (buf, pos, 0, flags, "w");
+
+  Lstream_set_character_mode (XLSTREAM (lstr));
+  return lstr;
+}
+
+static int
+lisp_buffer_reader (Lstream *stream, unsigned char *data, int size)
+{
+  struct lisp_buffer_stream *str = LISP_BUFFER_STREAM_DATA (stream);
+  unsigned char *orig_data = data;
+  Bytind start;
+  Bytind end;
+  struct buffer *buf = XBUFFER (str->buffer);
+
+  if (!BUFFER_LIVE_P (buf))
+    return 0; /* Fut. */
+
+  /* NOTE: We do all our operations in Bytind's.
+     Keep in mind that SIZE is a value in bytes, not chars. */
+
+  start = bi_marker_position (str->start);
+  end = bi_marker_position (str->end);
+  if (!(str->flags & LSTR_IGNORE_ACCESSIBLE))
+    {
+      start = bytind_clip_to_bounds (BI_BUF_BEGV (buf), start,
+				     BI_BUF_ZV (buf));
+      end = bytind_clip_to_bounds (BI_BUF_BEGV (buf), end,
+				   BI_BUF_ZV (buf));
+    }
+  
+  size = min (size, end - start);
+  end = start + size;
+  /* We cannot return a partial character. */
+  VALIDATE_BYTIND_BACKWARD (buf, end);
+
+  while (start < end)
+    {
+      Bytind ceil;
+      Bytecount chunk;
+
+      if (str->flags & LSTR_IGNORE_ACCESSIBLE)
+	ceil = BI_BUF_CEILING_OF_IGNORE_ACCESSIBLE (buf, start);
+      else
+	ceil = BI_BUF_CEILING_OF (buf, start);
+      chunk = min (ceil, end) - start;
+      memcpy (data, BI_BUF_BYTE_ADDRESS (buf, start), chunk);
+      data += chunk;
+      start += chunk;
+    }
+
+  if (EQ (buf->selective_display, Qt) && str->flags & LSTR_SELECTIVE)
+    {
+      /* What a kludge.  What a kludge.  What a kludge. */
+      unsigned char *p;
+      for (p = orig_data; p < data; p++)
+	if (*p == '\r')
+	  *p = '\n';
+    }
+
+  set_bi_marker_position (str->start, end);
+  return data - orig_data;
+}
+
+static int
+lisp_buffer_writer (Lstream *stream, CONST unsigned char *data, int size)
+{
+  struct lisp_buffer_stream *str = LISP_BUFFER_STREAM_DATA (stream);
+  Bufpos pos;
+  struct buffer *buf = XBUFFER (str->buffer);
+
+  if (!BUFFER_LIVE_P (buf))
+    return 0; /* Fut. */
+
+  pos = marker_position (str->start);
+  pos += buffer_insert_raw_string_1 (buf, pos, data, size, 0);
+  set_marker_position (str->start, pos);
+  return size;
+}
+
+static int
+lisp_buffer_rewinder (Lstream *stream)
+{
+  struct lisp_buffer_stream *str =
+    LISP_BUFFER_STREAM_DATA (stream);
+  struct buffer *buf = XBUFFER (str->buffer);
+  long pos = marker_position (str->orig_start);
+  if (!BUFFER_LIVE_P (buf))
+    return -1; /* Fut. */
+  if (pos > BUF_ZV (buf))
+    pos = BUF_ZV (buf);
+  if (pos < marker_position (str->orig_start))
+    pos = marker_position (str->orig_start);
+  if (MARKERP (str->end) && pos > marker_position (str->end))
+    pos = marker_position (str->end);
+  set_marker_position (str->start, pos);
+  return 0;
+}
+
+static Lisp_Object
+lisp_buffer_marker (Lisp_Object stream, void (*markobj) (Lisp_Object))
+{
+  struct lisp_buffer_stream *str =
+    LISP_BUFFER_STREAM_DATA (XLSTREAM (stream));
+
+  (markobj) (str->start);
+  (markobj) (str->end);
+  return str->buffer;
+}
+
+Bufpos
+lisp_buffer_stream_startpos (Lstream *stream)
+{
+  return marker_position (LISP_BUFFER_STREAM_DATA (stream)->start);
+}
+
+
+/************************************************************************/
+/*                            initialization                            */
+/************************************************************************/
+
+void
+lstream_type_create (void)
+{
+  LSTREAM_HAS_METHOD (stdio, reader);
+  LSTREAM_HAS_METHOD (stdio, writer);
+  LSTREAM_HAS_METHOD (stdio, rewinder);
+  LSTREAM_HAS_METHOD (stdio, seekable_p);
+  LSTREAM_HAS_METHOD (stdio, flusher);
+  LSTREAM_HAS_METHOD (stdio, closer);
+
+  LSTREAM_HAS_METHOD (filedesc, reader);
+  LSTREAM_HAS_METHOD (filedesc, writer);
+  LSTREAM_HAS_METHOD (filedesc, rewinder);
+  LSTREAM_HAS_METHOD (filedesc, seekable_p);
+  LSTREAM_HAS_METHOD (filedesc, closer);
+
+  LSTREAM_HAS_METHOD (lisp_string, reader);
+  LSTREAM_HAS_METHOD (lisp_string, rewinder);
+  LSTREAM_HAS_METHOD (lisp_string, marker);
+
+  LSTREAM_HAS_METHOD (fixed_buffer, reader);
+  LSTREAM_HAS_METHOD (fixed_buffer, writer);
+  LSTREAM_HAS_METHOD (fixed_buffer, rewinder);
+
+  LSTREAM_HAS_METHOD (resizing_buffer, writer);
+  LSTREAM_HAS_METHOD (resizing_buffer, rewinder);
+  LSTREAM_HAS_METHOD (resizing_buffer, closer);
+
+  LSTREAM_HAS_METHOD (dynarr, writer);
+  LSTREAM_HAS_METHOD (dynarr, rewinder);
+  LSTREAM_HAS_METHOD (dynarr, closer);
+
+  LSTREAM_HAS_METHOD (lisp_buffer, reader);
+  LSTREAM_HAS_METHOD (lisp_buffer, writer);
+  LSTREAM_HAS_METHOD (lisp_buffer, rewinder);
+  LSTREAM_HAS_METHOD (lisp_buffer, marker);
+}
+
+void
+vars_of_lstream (void)
+{
+  int i;
+
+  for (i = 0; i < countof (Vlstream_free_list); i++)
+    {
+      Vlstream_free_list[i] = Qnil;
+      staticpro (&Vlstream_free_list[i]);
+    }
+}