diff --git a/C/iopreds.c b/C/iopreds.c
index 931780199..d411dcbfd 100755
--- a/C/iopreds.c
+++ b/C/iopreds.c
@@ -272,6 +272,9 @@ yap_fflush(int sno)
 	  Socket_Stream_f|
 	  Pipe_Stream_f|
 	  Free_Stream_f)) ) {
+    if (Stream[sno].status & SWI_Stream_f) {
+      return SWIFlush(Stream[sno].u.swi_stream.swi_ptr);
+    }
     return(fflush(Stream[sno].u.file.file));
   } else
     return(0);
@@ -2697,7 +2700,7 @@ static Int p_change_alias_to_stream (void)
   if ((sno = CheckStream (tstream, Input_Stream_f | Output_Stream_f | Append_Stream_f | Socket_Stream_f,  "change_stream_alias/2")) == -1) {
     UNLOCK(Stream[sno].streamlock);
     return(FALSE);
-    }
+  }
   SetAlias(at, sno);
   UNLOCK(Stream[sno].streamlock);
   return(TRUE);
@@ -3647,14 +3650,13 @@ p_peek_byte (void)
     Yap_Error(PERMISSION_ERROR_INPUT_TEXT_STREAM, ARG1, "peek/2");
     return(FALSE);
   }
+  UNLOCK(Stream[sno].streamlock);
   if (Stream[sno].stream_getc == PlUnGetc) {
     ch = MkIntTerm(Stream[sno].och);
     /* sequence of peeks */
-    UNLOCK(Stream[sno].streamlock);
     return Yap_unify_constant(ARG2,ch);
   }
   if (status & Eof_Stream_f) {
-    UNLOCK(Stream[sno].streamlock);
     Yap_Error(PERMISSION_ERROR_INPUT_PAST_END_OF_STREAM, ARG1, "peek/2");
     return(FALSE);
   }
@@ -3698,17 +3700,20 @@ p_peek (void)
     Yap_Error(PERMISSION_ERROR_INPUT_BINARY_STREAM, ARG1, "peek/2");
     return FALSE;
   }
+  UNLOCK(Stream[sno].streamlock);
   if (Stream[sno].stream_getc == PlUnGetc) {
     ch = MkIntTerm(Stream[sno].och);
-    UNLOCK(Stream[sno].streamlock);
     /* sequence of peeks */
     return Yap_unify_constant(ARG2,ch);
   }
+  LOCK(Stream[sno].streamlock);
   s = Stream+sno;
   ocharcount = s->charcount;
   olinecount = s->linecount;
   olinepos = s->linepos;
+  UNLOCK(Stream[sno].streamlock);
   ch = get_wchar(sno);
+  LOCK(Stream[sno].streamlock);
   s->charcount = ocharcount;
   s->linecount = olinecount;
   s->linepos = olinepos;
@@ -4693,8 +4698,8 @@ p_get (void)
     Yap_Error(PERMISSION_ERROR_INPUT_BINARY_STREAM, ARG1, "get/2");
     return FALSE;
   }
-  while ((ch = Stream[sno].stream_wgetc(sno)) <= 32 && ch >= 0);
   UNLOCK(Stream[sno].streamlock);
+  while ((ch = Stream[sno].stream_wgetc(sno)) <= 32 && ch >= 0);
   return (Yap_unify_constant (ARG2, MkIntegerTerm (ch)));
 }
 
@@ -4713,8 +4718,8 @@ p_get0 (void)
     Yap_Error(PERMISSION_ERROR_INPUT_BINARY_STREAM, ARG1, "get0/2");
     return FALSE;
   }
-  out = Stream[sno].stream_wgetc(sno);
   UNLOCK(Stream[sno].streamlock);
+  out = Stream[sno].stream_wgetc(sno);
   return (Yap_unify_constant (ARG2, MkIntegerTerm (out)) );
 }
 
@@ -4754,8 +4759,8 @@ p_get0_line_codes (void)
     Yap_Error(PERMISSION_ERROR_INPUT_BINARY_STREAM, ARG1, "get0/2");
     return FALSE;
   }
-  out = read_line(sno);
   UNLOCK(Stream[sno].streamlock);
+  out = read_line(sno);
   if (rewind) 
     return Yap_unify(MkPairTerm(MkIntegerTerm(ch),out), ARG2);
   else
@@ -5816,8 +5821,8 @@ p_skip (void)
     UNLOCK(Stream[sno].streamlock);
     return (FALSE);
   }
-  while ((ch = Stream[sno].stream_wgetc(sno)) != n && ch != -1);
   UNLOCK(Stream[sno].streamlock);
+  while ((ch = Stream[sno].stream_wgetc(sno)) != n && ch != -1);
   return (TRUE);
 }
 
diff --git a/H/YapHeap.h b/H/YapHeap.h
index 40eb0cfd9..69401f969 100755
--- a/H/YapHeap.h
+++ b/H/YapHeap.h
@@ -27,6 +27,7 @@ typedef int (*SWI_GetFunction)(void *);
 typedef int (*SWI_PutWideFunction)(int, void *);
 typedef int (*SWI_GetWideFunction)(void *);
 typedef int (*SWI_CloseFunction)(void *);
+typedef int (*SWI_FlushFunction)(void *);
 
 #include "../include/dswiatoms.h"
 
@@ -105,6 +106,10 @@ typedef struct restore_info {
   ADDR old_HeapTop;
 } restoreinfo;
 
+/* SWI Emulation */
+#define SWI_BUF_SIZE 512
+#define SWI_TMP_BUF_SIZE 2*SWI_BUF_SIZE
+#define SWI_BUF_RINGS 16
 
 #ifdef THREADS
 typedef struct thandle {
diff --git a/H/dglobals.h b/H/dglobals.h
index 293e497b1..31d5a6ebd 100644
--- a/H/dglobals.h
+++ b/H/dglobals.h
@@ -149,6 +149,9 @@
 #define putc_cur_buf WL->putc_cur_buf_
 #define putc_cur_lim WL->putc_cur_lim_
 #define putc_cur_flags WL->putc_cur_flags_
+#define SWI_buffers WL->SWI_buffers_
+#define SWI_buffers_sz WL->SWI_buffers_sz_
+#define SWI_buf_index WL->SWI_buf_index_
 #define execution WL->_execution
 
 #if (defined(YAPOR) || defined(TABLING)) && defined(THREADS)
@@ -183,6 +186,7 @@
 #define SWIWideGetc Yap_global->swi_wgetc
 #define SWIWidePutc Yap_global->swi_wputc
 #define SWIClose Yap_global->swi_close
+#define SWIFlush Yap_global->swi_flush
 
 #define Yap_AllowLocalExpansion Yap_global->allow_local_expansion
 #define Yap_AllowGlobalExpansion Yap_global->allow_global_expansion
diff --git a/H/hglobals.h b/H/hglobals.h
index 8c5a8624a..e825d712d 100644
--- a/H/hglobals.h
+++ b/H/hglobals.h
@@ -151,6 +151,9 @@ typedef struct worker_local {
   char*  putc_cur_buf_;
   char*  putc_cur_lim_;
   UInt  putc_cur_flags_;
+  char*  SWI_buffers_[1+SWI_BUF_RINGS];
+  size_t  SWI_buffers_sz_[1+SWI_BUF_RINGS];
+  int  SWI_buf_index_;
   struct open_query_struct*  _execution;
 
 #if (defined(YAPOR) || defined(TABLING)) && defined(THREADS)
@@ -185,6 +188,7 @@ typedef struct worker_shared {
   SWI_GetWideFunction  swi_wgetc;
   SWI_PutWideFunction  swi_wputc;
   SWI_CloseFunction  swi_close;
+  SWI_FlushFunction  swi_flush;
 
   int  allow_local_expansion;
   int  allow_global_expansion;
diff --git a/H/iglobals.h b/H/iglobals.h
index 44c4b0e9a..08cf8a73c 100644
--- a/H/iglobals.h
+++ b/H/iglobals.h
@@ -149,6 +149,9 @@ static void InitWorker(int wid) {
   FOREIGN_WL(wid)->putc_cur_buf_ = NULL;
   FOREIGN_WL(wid)->putc_cur_lim_ = NULL;
   FOREIGN_WL(wid)->putc_cur_flags_ = 0L;
+  InitSWIBuffers(wid);
+
+  FOREIGN_WL(wid)->SWI_buf_index_ = 0;
   FOREIGN_WL(wid)->_execution = NULL;
 
 #if (defined(YAPOR) || defined(TABLING)) && defined(THREADS)
@@ -183,6 +186,7 @@ static void InitGlobal(void) {
   Yap_global->swi_wgetc = NULL;
   Yap_global->swi_wputc = NULL;
   Yap_global->swi_close = NULL;
+  Yap_global->swi_flush = NULL;
 
   Yap_global->allow_local_expansion = TRUE;
   Yap_global->allow_global_expansion = TRUE;
diff --git a/H/rglobals.h b/H/rglobals.h
index be46ef1f7..06fcdd842 100644
--- a/H/rglobals.h
+++ b/H/rglobals.h
@@ -151,6 +151,9 @@ static void RestoreWorker(int wid) {
 
 
 
+
+
+
 #if (defined(YAPOR) || defined(TABLING)) && defined(THREADS)
 
 #endif
@@ -194,6 +197,7 @@ static void RestoreGlobal(void) {
 
 
 
+
 #if HAVE_LIBREADLINE
 
 
diff --git a/include/SWI-Prolog.h b/include/SWI-Prolog.h
index b5ef74982..d439a1ca6 100755
--- a/include/SWI-Prolog.h
+++ b/include/SWI-Prolog.h
@@ -669,6 +669,7 @@ typedef struct SWI_IO {
   void *put_c;
   void *get_w;
   void *put_w;
+  void *flush_s;
   void *close_s;
 } swi_io_struct;
 
diff --git a/library/Makefile.in b/library/Makefile.in
index 4080a3cc1..af5c2a2ad 100644
--- a/library/Makefile.in
+++ b/library/Makefile.in
@@ -91,7 +91,8 @@ DIALECT_PROGRAMS= \
 
 DIALECT_SWI= \
 	$(srcdir)/dialect/swi/INDEX.pl \
-	$(srcdir)/dialect/swi/listing.pl
+	$(srcdir)/dialect/swi/listing.pl \
+	$(srcdir)/dialect/swi/readutil.pl
 
 
 install: $(PROGRAMS) install_myddas
diff --git a/library/dialect/swi/readutil.pl b/library/dialect/swi/readutil.pl
new file mode 100644
index 000000000..3ce0ca5d2
--- /dev/null
+++ b/library/dialect/swi/readutil.pl
@@ -0,0 +1,242 @@
+/*  $Id$
+
+    Part of SWI-Prolog
+
+    Author:        Jan Wielemaker
+    E-mail:        jan@swi.psy.uva.nl
+    WWW:           http://www.swi-prolog.org
+    Copyright (C): 1985-2002, University of Amsterdam
+
+    This program 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
+    of the License, or (at your option) any later version.
+
+    This program 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 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
+
+    As a special exception, if you link this library with other files,
+    compiled with a Free Software compiler, to produce an executable, this
+    library does not by itself cause the resulting executable to be covered
+    by the GNU General Public License. This exception does not however
+    invalidate any other reasons why the executable file might be covered by
+    the GNU General Public License.
+*/
+
+:- module(read_util,
+	  [ read_line_to_codes/2,	% +Fd, -Codes (without trailing \n)
+	    read_line_to_codes/3,	% +Fd, -Codes, ?Tail
+	    read_stream_to_codes/2,	% +Fd, -Codes
+	    read_stream_to_codes/3,	% +Fd, -Codes, ?Tail
+	    read_file_to_codes/3,	% +File, -Codes, +Options
+	    read_file_to_terms/3	% +File, -Terms, +Options
+	  ]).
+:- use_module(library(shlib)).
+:- use_module(library(lists), [select/3]).
+:- use_module(library(error)).
+
+/** <module> Read utilities
+
+This library provides some commonly used   reading  predicates. As these
+predicates have proven to be time-critical in some applications we moved
+them to C. For compatibility as well  as to reduce system dependency, we
+link  the  foreign  code  at  runtime    and   fallback  to  the  Prolog
+implementation if the shared object cannot be found.
+*/
+
+:- volatile
+	read_line_to_codes/2,
+	read_line_to_codes/3,
+	read_stream_to_codes/2,
+	read_stream_to_codes/3.
+
+link_foreign :-
+	catch(load_foreign_library(foreign(readutil)), _, fail), !.
+link_foreign :-
+	assertz((read_line_to_codes(Stream, Line) :-
+		pl_read_line_to_codes(Stream, Line))),
+	assertz((read_line_to_codes(Stream, Line, Tail) :-
+		pl_read_line_to_codes(Stream, Line, Tail))),
+	assertz((read_stream_to_codes(Stream, Content) :-
+	        pl_read_stream_to_codes(Stream, Content))),
+	assertz((read_stream_to_codes(Stream, Content, Tail) :-
+	        pl_read_stream_to_codes(Stream, Content, Tail))),
+	compile_predicates([ read_line_to_codes/2,
+			     read_line_to_codes/3,
+			     read_stream_to_codes/2,
+			     read_stream_to_codes/3
+			   ]).
+
+:- initialization(link_foreign, now).
+
+
+		 /*******************************
+		 *	       LINES		*
+		 *******************************/
+
+%%	read_line_to_codes(+In:stream, -Line:codes) is det.
+%
+%	Read a line of input from  In   into  a list of character codes.
+%	Trailing newline and  or  return   are  deleted.  Upon  reaching
+%	end-of-file Line is unified to the atom =end_of_file=.
+
+pl_read_line_to_codes(Fd, Codes) :-
+	get_code(Fd, C0),
+	(   C0 == -1
+	->  Codes = end_of_file
+	;   read_1line_to_codes(C0, Fd, Codes0)
+	),
+	Codes = Codes0.
+
+read_1line_to_codes(-1, _, []) :- !.
+read_1line_to_codes(10, _, []) :- !.
+read_1line_to_codes(13, Fd, L) :- !,
+	get_code(Fd, C2),
+	read_1line_to_codes(C2, Fd, L).
+read_1line_to_codes(C, Fd, [C|T]) :-
+	get_code(Fd, C2),
+	read_1line_to_codes(C2, Fd, T).
+
+%%	read_line_to_codes(+Fd, -Line, ?Tail) is det.
+%
+%	Read a line of input as a   difference list. This should be used
+%	to read multiple lines  efficiently.   On  reaching end-of-file,
+%	Tail is bound to the empty list.
+
+pl_read_line_to_codes(Fd, Codes, Tail) :-
+	get_code(Fd, C0),
+	read_line_to_codes(C0, Fd, Codes0, Tail),
+	Codes = Codes0.
+
+read_line_to_codes(-1, _, Tail, Tail) :- !,
+	Tail = [].
+read_line_to_codes(10, _, [10|Tail], Tail) :- !.
+read_line_to_codes(C, Fd, [C|T], Tail) :-
+	get_code(Fd, C2),
+	read_line_to_codes(C2, Fd, T, Tail).
+
+
+		 /*******************************
+		 *     STREAM (ENTIRE INPUT)	*
+		 *******************************/
+
+%%	read_stream_to_codes(+Stream, -Codes) is det.
+%%	read_stream_to_codes(+Stream, -Codes, ?Tail) is det.
+%
+%	Read input from Stream to a list of character codes. The version
+%	read_stream_to_codes/3 creates a difference-list.
+
+pl_read_stream_to_codes(Fd, Codes) :-
+	pl_read_stream_to_codes(Fd, Codes, []).
+pl_read_stream_to_codes(Fd, Codes, Tail) :-
+	get_code(Fd, C0),
+	read_stream_to_codes(C0, Fd, Codes0, Tail),
+	Codes = Codes0.
+
+read_stream_to_codes(-1, _, Tail, Tail) :- !.
+read_stream_to_codes(C, Fd, [C|T], Tail) :-
+	get_code(Fd, C2),
+	read_stream_to_codes(C2, Fd, T, Tail).
+
+
+%%	read_stream_to_terms(+Stream, -Terms, ?Tail, +Options) is det.
+
+read_stream_to_terms(Fd, Terms, Tail, Options) :-
+	read_term(Fd, C0, Options),
+	read_stream_to_terms(C0, Fd, Terms0, Tail, Options),
+	Terms = Terms0.
+
+read_stream_to_terms(end_of_file, _, Tail, Tail, _) :- !.
+read_stream_to_terms(C, Fd, [C|T], Tail, Options) :-
+	read_term(Fd, C2, Options),
+	read_stream_to_terms(C2, Fd, T, Tail, Options).
+
+
+		 /*******************************
+		 *      FILE (ENTIRE INPUT)	*
+		 *******************************/
+
+%%	read_file_to_codes(+Spec, -Codes, +Options) is det.
+%
+%	Read the file Spec into a list of Codes.  Options is split into
+%	options for absolute_file_name/3 and open/4.
+
+read_file_to_codes(Spec, Codes, Options) :-
+	must_be(proper_list, Options),
+	(   select(tail(Tail), Options, Options1)
+	->  true
+	;   Tail = [],
+	    Options1 = Options
+	),
+	split_options(Options1, file_option, FileOptions, OpenOptions),
+	absolute_file_name(Spec,
+			   [ access(read)
+			   | FileOptions
+			   ],
+			   Path),
+	open(Path, read, Fd, OpenOptions),
+	call_cleanup(read_stream_to_codes(Fd, Codes0, Tail),
+		     close(Fd)),
+	Codes = Codes0.
+
+
+%%	read_file_to_terms(+Spec, -Terms, +Options) is det.
+%
+%	Read the file Spec into a list   of terms. Options is split over
+%	absolute_file_name/3, open/4 and read_term/3.
+
+read_file_to_terms(Spec, Terms, Options) :-
+	must_be(proper_list, Options),
+	(   select(tail(Tail), Options, Options1)
+	->  true
+	;   Tail = [],
+	    Options1 = Options
+	),
+	split_options(Options1, file_option, FileOptions, Options2),
+	split_options(Options2, read_option, ReadOptions, OpenOptions),
+	absolute_file_name(Spec,
+			   [ access(read)
+			   | FileOptions
+			   ],
+			   Path),
+	open(Path, read, Fd, OpenOptions),
+	call_cleanup(read_stream_to_terms(Fd, Terms0, Tail, ReadOptions),
+		     close(Fd)),
+	Terms = Terms0.
+
+split_options([], _, [], []).
+split_options([H|T], G, File, Open) :-
+	(   call(G, H)
+	->  File = [H|FT],
+	    OT = Open
+	;   Open = [H|OT],
+	    FT = File
+	),
+	split_options(T, G, FT, OT).
+
+
+read_option(module(_)).
+read_option(syntax_errors(_)).
+read_option(character_escapes(_)).
+read_option(double_quotes(_)).
+read_option(backquoted_string(_)).
+
+file_option(extensions(_)).
+file_option(file_type(_)).
+file_option(file_errors(_)).
+file_option(relative_to(_)).
+file_option(expand(_)).
+
+		 /*******************************
+		 *	       XREF		*
+		 *******************************/
+
+:- multifile prolog:meta_goal/2.
+:- dynamic prolog:meta_goal/2.
+prolog:meta_goal(split_options(_,G,_,_), [G+1]).
diff --git a/library/yap2swi/yap2swi.c b/library/yap2swi/yap2swi.c
index 174a46c59..d1d841965 100755
--- a/library/yap2swi/yap2swi.c
+++ b/library/yap2swi/yap2swi.c
@@ -45,10 +45,6 @@
 #include <fcntl.h>
 #endif
 
-#define BUF_SIZE 512
-#define TMP_BUF_SIZE 2*BUF_SIZE
-#define BUF_RINGS 16
-
 /* Required by PL_error */
 #define ERR_NO_ERROR		0
 #define ERR_INSTANTIATION	1	/* void */
@@ -247,25 +243,21 @@ UserCPredicate(char *a, CPredicate def, unsigned long int arity, Term mod, int f
   CurrentModule = cm;
 } 
 
-static char *buffers[1+BUF_RINGS];
-static size_t buffers_sz[1+BUF_RINGS];
-static int buf_index = 0;
-
 static char *
 alloc_ring_buf(void)
 {
-  buf_index++;
-  if (buf_index == BUF_RINGS)
-    buf_index = 0;
-  if (buffers_sz[buf_index+1] == 0) {
+  SWI_buf_index++;
+  if (SWI_buf_index == SWI_BUF_RINGS)
+    SWI_buf_index = 0;
+  if (SWI_buffers_sz[SWI_buf_index+1] == 0) {
     char * new;
     if (!(new = malloc(512))) {
       return NULL;
     }
-    buffers_sz[buf_index+1] = 512;
-    buffers[buf_index+1] = new;
+    SWI_buffers_sz[SWI_buf_index+1] = 512;
+    SWI_buffers[SWI_buf_index+1] = new;
   }
-  return buffers[buf_index+1];
+  return SWI_buffers[SWI_buf_index+1];
 }
 
 static char *
@@ -274,7 +266,7 @@ ensure_space(char **sp, size_t room, unsigned flags) {
   int i = 0;
   char *ptr = *sp;
 
-  if (room < BUF_SIZE)
+  if (room < SWI_BUF_SIZE)
     return *sp;
   while (min < room)
     min += 512;
@@ -284,21 +276,21 @@ ensure_space(char **sp, size_t room, unsigned flags) {
     *sp = malloc(room);
     return *sp; 
   } else if (flags & BUF_RING) {
-    for (i=1; i<= BUF_RINGS; i++)
-      if (buffers[i] == ptr)
+    for (i=1; i<= SWI_BUF_RINGS; i++)
+      if (SWI_buffers[i] == ptr)
 	break;
   } else {
     i = 0;
   }
-  if (buffers_sz[i] >= room)
+  if (SWI_buffers_sz[i] >= room)
     return ptr;
-  free(buffers[i]);
-  buffers[i] = malloc(min);
-  if (buffers[i]) 
-    buffers_sz[i] = min;
+  free(SWI_buffers[i]);
+  SWI_buffers[i] = malloc(min);
+  if (SWI_buffers[i]) 
+    SWI_buffers_sz[i] = min;
   else
-    buffers_sz[i] = 0;
-  *sp = buffers[i];
+    SWI_buffers_sz[i] = 0;
+  *sp = SWI_buffers[i];
   return *sp;
 }
 
@@ -520,12 +512,12 @@ static int do_yap_putc(int sno, wchar_t ch) {
     UInt bufsize = putc_cur_lim-putc_cur_buf;
     UInt bufpos = putc_curp-putc_cur_buf;
 
-    if (!(putc_cur_buf = realloc(putc_cur_buf, bufsize+BUF_SIZE))) {
+    if (!(putc_cur_buf = realloc(putc_cur_buf, bufsize+SWI_BUF_SIZE))) {
       /* we can+t go forever */
       return FALSE;
     }
     putc_curp = putc_cur_buf+bufpos;
-    putc_cur_lim = putc_cur_buf+(bufsize+BUF_SIZE);
+    putc_cur_lim = putc_cur_buf+(bufsize+SWI_BUF_SIZE);
     return do_yap_putc(sno, ch);
   }
   return FALSE;
@@ -539,9 +531,9 @@ CvtToGenericTerm(Term t, char *tmp, unsigned flags, char **sp)
   putc_cur_buf = putc_curp = tmp;
   putc_cur_flags = flags;
   if ((flags & BUF_RING)) {
-    putc_cur_lim = tmp+(TMP_BUF_SIZE-1);
+    putc_cur_lim = tmp+(SWI_TMP_BUF_SIZE-1);
   } else {
-    putc_cur_lim = tmp+(BUF_SIZE-1);
+    putc_cur_lim = tmp+(SWI_BUF_SIZE-1);
   }
   if (flags & CVT_WRITE_CANONICAL) {
     wflags |= (YAP_WRITE_IGNORE_OPS|YAP_WRITE_QUOTED);
@@ -572,9 +564,9 @@ X_API int PL_get_chars(term_t l, char **sp, unsigned flags)
   if ((flags & BUF_RING)) {
     tmp = alloc_ring_buf();
   } else if ((flags & BUF_MALLOC)) {
-    tmp = malloc(BUF_SIZE);
+    tmp = malloc(SWI_BUF_SIZE);
   } else {
-    tmp = buffers[0];
+    tmp = SWI_buffers[0];
   }
   *sp = tmp;
   if (IsVarTerm(t)) {
@@ -602,21 +594,21 @@ X_API int PL_get_chars(term_t l, char **sp, unsigned flags)
     if (IsFloatTerm(t)) {
       if (!(flags & (CVT_FLOAT|CVT_NUMBER|CVT_ATOMIC|CVT_WRITE|CVT_WRITE_CANONICAL|CVT_ALL)))
 	return cv_error(flags);
-      snprintf(tmp,BUF_SIZE,"%f",FloatOfTerm(t));
+      snprintf(tmp,SWI_BUF_SIZE,"%f",FloatOfTerm(t));
     } else {
       if (!(flags & (CVT_INTEGER|CVT_NUMBER|CVT_ATOMIC|CVT_WRITE|CVT_WRITE_CANONICAL|CVT_ALL)))
 	return cv_error(flags);
 #if _WIN64
-      snprintf(tmp,BUF_SIZE,"%I64d",IntegerOfTerm(t));
+      snprintf(tmp,SWI_BUF_SIZE,"%I64d",IntegerOfTerm(t));
 #else
-      snprintf(tmp,BUF_SIZE,"%ld",IntegerOfTerm(t));
+      snprintf(tmp,SWI_BUF_SIZE,"%ld",IntegerOfTerm(t));
 #endif
     }
   } else if (IsPairTerm(t))  {
     if (!(flags & (CVT_LIST|CVT_WRITE|CVT_WRITE_CANONICAL|CVT_ALL))) { 
       return cv_error(flags);
     }
-    if (CvtToStringTerm(t,tmp,tmp+BUF_SIZE) == 0) {
+    if (CvtToStringTerm(t,tmp,tmp+SWI_BUF_SIZE) == 0) {
       if (flags & (CVT_WRITE|CVT_WRITE_CANONICAL)) {
 	if (!CvtToGenericTerm(t, tmp, flags, sp))
 	  return 0;
@@ -628,13 +620,13 @@ X_API int PL_get_chars(term_t l, char **sp, unsigned flags)
     if (IsBigIntTerm(t)) {
       if (!(flags & (CVT_INTEGER|CVT_NUMBER|CVT_ATOMIC|CVT_WRITE|CVT_WRITE_CANONICAL|CVT_ALL)))
 	return cv_error(flags);
-      Yap_gmp_to_string(t, tmp, BUF_SIZE-1, 10);
+      Yap_gmp_to_string(t, tmp, SWI_BUF_SIZE-1, 10);
     } else if (IsBlobStringTerm(t)) {
       if (!(flags & (CVT_STRING|CVT_WRITE|CVT_WRITE_CANONICAL|CVT_ALL))) {
 	return cv_error(flags);
       } else {
 	char *s = Yap_BlobStringOfTerm(t);
-	strncat(tmp, s, BUF_SIZE-1);
+	strncat(tmp, s, SWI_BUF_SIZE-1);
       } 
     } else {
       if (!(flags & (CVT_WRITE|CVT_WRITE_CANONICAL))) {
@@ -683,9 +675,10 @@ X_API int PL_get_wchars(term_t l, size_t *len, wchar_t **wsp, unsigned flags)
     sz = wcslen(wbuf);
     *len = sz;
   } else {
-    if (!PL_get_nchars(l, len, &sp, nflags))
+    if (!PL_get_nchars(l, &sz, &sp, nflags))
       return 0;
-    sz = *len;
+    if (len)
+      *len = sz;
   }
   room = (sz+1)*sizeof(wchar_t);
   if (flags & BUF_MALLOC) {
@@ -694,7 +687,7 @@ X_API int PL_get_wchars(term_t l, size_t *len, wchar_t **wsp, unsigned flags)
     *wsp = (wchar_t *)alloc_ring_buf();
     buf = (wchar_t *)ensure_space((char **)wsp, room, flags);
   } else {
-    *wsp = (wchar_t *)buffers[0];
+    *wsp = (wchar_t *)SWI_buffers[0];
     buf = (wchar_t *)ensure_space((char **)wsp, room, flags);
   }
   if (!buf) {
@@ -706,9 +699,9 @@ X_API int PL_get_wchars(term_t l, size_t *len, wchar_t **wsp, unsigned flags)
     wcsncpy(buf, wbuf, sz);
   } else {
     sp0 = sp;
+    buf[sz] = '\0';
     for (i=0; i< sz; i++)
       *buf++ = *sp++;
-    buf[sz] = '\0';
     free(sp0);
   }
   return 1;
@@ -1133,7 +1126,7 @@ X_API int PL_cons_functor(term_t d, functor_t f,...)
 {
   va_list ap;
   int arity, i;
-  Term *tmp = (Term *)buffers[0];
+  Term *tmp = (Term *)SWI_buffers[0];
   Functor ff = SWIFunctorToFunctor(f);
 
   if (IsAtomTerm((Term)ff)) {
@@ -1141,7 +1134,7 @@ X_API int PL_cons_functor(term_t d, functor_t f,...)
     return TRUE;
   }
   arity = ArityOfFunctor(ff);
-  if (arity > TMP_BUF_SIZE/sizeof(YAP_CELL)) {
+  if (arity > SWI_TMP_BUF_SIZE/sizeof(YAP_CELL)) {
     fprintf(stderr,"PL_cons_functor: arity too large (%d)\n", arity); 
     return FALSE;
   }
@@ -3240,6 +3233,7 @@ PL_YAP_InitSWIIO(struct SWI_IO *swio)
   SWIPutc = swio->put_c;
   SWIWideGetc = swio->get_w;
   SWIWidePutc = swio->put_w;
+  SWIFlush = swio->flush_s;
   SWIClose = swio->close_s;
 }
 
@@ -3259,14 +3253,6 @@ void Yap_swi_install(void);
 void
 Yap_swi_install(void)
 {
-  int i;
-
-  buffers[0] = malloc(BUF_SIZE);
-  buffers_sz[0] = BUF_SIZE;
-  for (i=1; i <= BUF_RINGS; i++) {
-    buffers[i] = NULL;
-    buffers_sz[i] = 0;
-  }
   YAP_UserCPredicate("ctime", SWI_ctime, 2);
 }
 
diff --git a/misc/GLOBALS b/misc/GLOBALS
index 3cc824da7..8d1d2e35b 100644
--- a/misc/GLOBALS
+++ b/misc/GLOBALS
@@ -163,6 +163,10 @@ char*				putc_curp_		putc_curp		=NULL
 char*				putc_cur_buf_		putc_cur_buf		=NULL
 char*				putc_cur_lim_		putc_cur_lim		=NULL
 UInt				putc_cur_flags_		putc_cur_flags		=0L
+char*				SWI_buffers_[1+SWI_BUF_RINGS] SWI_buffers	InitSWIBuffers(wid)
+size_t				SWI_buffers_sz_[1+SWI_BUF_RINGS] SWI_buffers_sz	void
+int				SWI_buf_index_		SWI_buf_index		=0
+
 
 struct open_query_struct*	_execution		execution		=NULL
 
@@ -205,6 +209,7 @@ SWI_PutFunction		swi_putc		SWIPutc		=NULL
 SWI_GetWideFunction	swi_wgetc		SWIWideGetc	=NULL
 SWI_PutWideFunction	swi_wputc		SWIWidePutc	=NULL
 SWI_CloseFunction	swi_close		SWIClose	=NULL
+SWI_FlushFunction	swi_flush		SWIFlush	=NULL
 
 // stack overflow expansion/gc control
 int		allow_local_expansion	Yap_AllowLocalExpansion =TRUE
diff --git a/packages/PLStream/pl-file.c b/packages/PLStream/pl-file.c
index 5298edf04..6ab14d059 100755
--- a/packages/PLStream/pl-file.c
+++ b/packages/PLStream/pl-file.c
@@ -4322,6 +4322,7 @@ init_yap_extras()
   swiio.put_c = Sputc;
   swiio.get_w = Sgetcode;
   swiio.put_w = Sputcode;
+  swiio.flush_s = Sflush;
   swiio.close_s = Sclose;
   PL_YAP_InitSWIIO(&swiio);
   initCharTypes();
diff --git a/packages/PLStream/pl-incl.h b/packages/PLStream/pl-incl.h
index 9bfbc5937..aa7b99cca 100755
--- a/packages/PLStream/pl-incl.h
+++ b/packages/PLStream/pl-incl.h
@@ -128,6 +128,12 @@ typedef struct {
   { Table       table;                  /* global (read-only) features */
   } prolog_flag;
 
+#if THREADS
+  struct
+  { int		    	enabled;	/* threads are enabled */
+  } thread;
+#endif
+
   struct
   { Table		tmp_files;	/* Known temporary files */
     CanonicalDir	_canonical_dirlist;
@@ -387,8 +393,70 @@ extern PL_local_data_t lds;
 
 
 /* Support PL_LOCK in the interface */
-#define PL_LOCK(X)
-#define PL_UNLOCK(X)
+#if THREADS
+
+typedef pthread_mutex_t simpleMutex;
+
+#define simpleMutexInit(p)	pthread_mutex_init(p, NULL)
+#define simpleMutexDelete(p)	pthread_mutex_destroy(p)
+#define simpleMutexLock(p)	pthread_mutex_lock(p)
+#define simpleMutexUnlock(p)	pthread_mutex_unlock(p)
+
+extern counting_mutex _PL_mutexes[];	/* Prolog mutexes */
+
+#define L_MISC		0
+#define L_ALLOC		1
+#define L_ATOM		2
+#define L_FLAG	        3
+#define L_FUNCTOR	4
+#define L_RECORD	5
+#define L_THREAD	6
+#define L_PREDICATE	7
+#define L_MODULE	8
+#define L_TABLE		9
+#define L_BREAK	       10
+#define L_FILE	       11
+#define L_PLFLAG      12
+#define L_OP	       13
+#define L_INIT	       14
+#define L_TERM	       15
+#define L_GC	       16
+#define L_AGC	       17
+#define L_FOREIGN      18
+#define L_OS	       19
+
+#define IF_MT(id, g) if ( id == L_THREAD || GD->thread.enabled ) g
+
+#ifdef O_CONTENTION_STATISTICS
+#define countingMutexLock(cm) \
+	do \
+	{ if ( pthread_mutex_trylock(&(cm)->mutex) == EBUSY ) \
+	  { (cm)->collisions++; \
+	    pthread_mutex_lock(&(cm)->mutex); \
+	  } \
+	  (cm)->count++; \
+	} while(0)
+#else
+#define countingMutexLock(cm) \
+	do \
+	{ simpleMutexLock(&(cm)->mutex); \
+	  (cm)->count++; \
+	} while(0)
+#endif
+#define countingMutexUnlock(cm) \
+	do \
+	{ (cm)->unlocked++; \
+	  assert((cm)->unlocked <= (cm)->count); \
+	  simpleMutexUnlock(&(cm)->mutex); \
+	} while(0)
+
+#define PL_LOCK(id)   IF_MT(id, countingMutexLock(&_PL_mutexes[id]))
+#define PL_UNLOCK(id) IF_MT(id, countingMutexUnlock(&_PL_mutexes[id]))
+
+#else
+#define PL_LOCK(X)		
+#define PL_UNLOCK(X)		
+#endif
 
 
 #ifndef TRUE
@@ -658,6 +726,9 @@ void initFiles(void);
 int RemoveFile(const char *path);
 int PL_get_file_name(term_t n, char **namep, int flags);
 
+/**** stuff from pl-utf8.c ****/
+size_t utf8_strlen(const char *s, size_t len);
+
 /* empty stub */
 void setPrologFlag(const char *name, int flags, ...);
 void PL_set_prolog_flag(const char *name, int flags, ...);
diff --git a/packages/PLStream/pl-yap.c b/packages/PLStream/pl-yap.c
index e3aff0132..7e98fdb0a 100644
--- a/packages/PLStream/pl-yap.c
+++ b/packages/PLStream/pl-yap.c
@@ -133,7 +133,9 @@ callProlog(module_t module, term_t goal, int flags, term_t *ex)
   }
 }
 
-int
+extern X_API int PL_write_term(IOSTREAM *s, term_t term, int precedence, int flags);
+
+X_API int 
 PL_write_term(IOSTREAM *s, term_t term, int precedence, int flags)
 {
   int nflags = 0;
@@ -709,10 +711,41 @@ PL_dispatch(int fd, int wait)
   return TRUE;
 }
 
-extern  size_t PL_utf8_strlen(const char *s, size_t len);
+extern size_t PL_utf8_strlen(const char *s, size_t len);
 
 X_API size_t
 PL_utf8_strlen(const char *s, size_t len)
 { return utf8_strlen(s, len);
 }
 
+#define COUNT_MUTEX_INITIALIZER(name) \
+ { PTHREAD_MUTEX_INITIALIZER, \
+   name, \
+   0L \
+ }
+
+#if THREADS
+counting_mutex _PL_mutexes[] =
+{ COUNT_MUTEX_INITIALIZER("L_MISC"),
+  COUNT_MUTEX_INITIALIZER("L_ALLOC"),
+  COUNT_MUTEX_INITIALIZER("L_ATOM"),
+  COUNT_MUTEX_INITIALIZER("L_FLAG"),
+  COUNT_MUTEX_INITIALIZER("L_FUNCTOR"),
+  COUNT_MUTEX_INITIALIZER("L_RECORD"),
+  COUNT_MUTEX_INITIALIZER("L_THREAD"),
+  COUNT_MUTEX_INITIALIZER("L_PREDICATE"),
+  COUNT_MUTEX_INITIALIZER("L_MODULE"),
+  COUNT_MUTEX_INITIALIZER("L_TABLE"),
+  COUNT_MUTEX_INITIALIZER("L_BREAK"),
+  COUNT_MUTEX_INITIALIZER("L_FILE"),
+  COUNT_MUTEX_INITIALIZER("L_PLFLAG"),
+  COUNT_MUTEX_INITIALIZER("L_OP"),
+  COUNT_MUTEX_INITIALIZER("L_INIT"),
+  COUNT_MUTEX_INITIALIZER("L_TERM"),
+  COUNT_MUTEX_INITIALIZER("L_GC"),
+  COUNT_MUTEX_INITIALIZER("L_AGC"),
+  COUNT_MUTEX_INITIALIZER("L_FOREIGN"),
+  COUNT_MUTEX_INITIALIZER("L_OS")
+};
+
+#endif
diff --git a/packages/PLStream/pl-yap.h b/packages/PLStream/pl-yap.h
index 6bb76e9ef..2d8198c21 100644
--- a/packages/PLStream/pl-yap.h
+++ b/packages/PLStream/pl-yap.h
@@ -97,7 +97,7 @@ YAP_Int YAP_PLArityOfSWIFunctor(functor_t f);
 #define valReal(w) YAP_FloatOfTerm((w))
 #define valFloat(w) YAP_FloatOfTerm((w))
 #define AtomLength(w) YAP_AtomNameLength(w)
-#define atomValue(atom) AtomOfTerm(atom)
+#define atomValue(atom) YAP_AtomOfTerm(atom)
 #define argTermP(w,i) ((Word)((YAP_ArgsOfTerm(w)+(i))))
 #define deRef(t) (t = YAP_Deref(t))
 #define canBind(t) FALSE
diff --git a/packages/zlib/test_zlib.pl b/packages/zlib/test_zlib.pl
index b9e6b6943..bc59c8c75 100644
--- a/packages/zlib/test_zlib.pl
+++ b/packages/zlib/test_zlib.pl
@@ -27,7 +27,7 @@ test(gunzip,
      ]) :-
 	gzopen('plunit-tmp.gz', read, ZIn),
 	call_cleanup(read_stream_to_codes(ZIn, Codes0), close(ZIn)),
-	read_file_to_codes('test_zlib.pl', Codes1),
+	this_read_file_to_codes('test_zlib.pl', Codes1),
 	Codes0 == Codes1.
 
 %	gzip: Can gunzip read our compressed file
@@ -35,11 +35,11 @@ test(gunzip,
 test(gzip,
      [ cleanup(delete_file('plunit-tmp.gz'))
      ]) :-
-	read_file_to_codes('test_zlib.pl', Codes),
+	this_read_file_to_codes('test_zlib.pl', Codes),
 	gzopen('plunit-tmp.gz', write, ZOut),
 	format(ZOut, '~s', [Codes]),
 	close(ZOut),
-	read_file_to_codes(pipe('gunzip < plunit-tmp.gz'), Codes1),
+	this_read_file_to_codes(pipe('gunzip < plunit-tmp.gz'), Codes1),
 	Codes == Codes1.
 
 %	deflate: test read/write of deflate format
@@ -47,12 +47,12 @@ test(gzip,
 test(deflate,
      [ cleanup(delete_file('plunit-tmp.z'))
      ]) :-
-	read_file_to_codes('test_zlib.pl', Codes),
-	open('plunit-tmp.z', write, Out),
+	this_read_file_to_codes('test_zlib.pl', Codes),
+	system:swi_open('plunit-tmp.z', write, Out),
 	zopen(Out, ZOut, []),
 	format(ZOut, '~s', [Codes]),
 	close(ZOut),
-	open('plunit-tmp.z', read, In),
+	system:swi_open('plunit-tmp.z', read, In),
 	zopen(In, ZIn, []),
 	read_stream_to_codes(ZIn, Codes1),
 	close(ZIn),
@@ -198,7 +198,7 @@ get_data(ZIn, N) :-
 		 *	       UTIL		*
 		 *******************************/
 
-read_file_to_codes(File, Codes) :-
-	open(File, read, In),
+this_read_file_to_codes(File, Codes) :-
+	system:swi_open(File, read, In),
 	call_cleanup(read_stream_to_codes(In, Codes), close(In)).