--- gforth/blocks.fs	1994/08/10 17:22:35	1.1
+++ gforth/blocks.fs	1999/03/29 22:52:27	1.23
@@ -1,89 +1,215 @@
-\ A simple immplementation of the blocks wordset. 
+\ A less simple implementation of the blocks wordset. 
 
-\ This implementation uses only a single buffer and will therefore be a
-\ little slow. An efficient implementation would use mmap on OSs that
+\ Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
+
+\ This file is part of Gforth.
+
+\ Gforth 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 General Public License
+\ along with this program; if not, write to the Free Software
+\ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+
+\ A more efficient implementation would use mmap on OSs that
 \ provide it and many buffers on OSs that do not provide mmap.
 
+\ Now, the replacement algorithm is "direct mapped"; change to LRU
+\ if too slow. Using more buffers helps, too.
+
 \ I think I avoid the assumption 1 char = 1 here, but I have not tested this
 
-1024 constant chars/block \ mandated by the standard
+\ 1024 constant chars/block \ mandated by the standard
+
+require struct.fs
+
+struct
+    cell%		field buffer-block   \ the block number
+    cell%		field buffer-fid     \ the block's fid
+    cell%		field buffer-dirty   \ the block dirty flag
+    char% chars/block * field block-buffer   \ the data
+    cell% 0 *		field next-buffer
+end-struct buffer-struct
+
+Variable block-buffers
+Variable last-block
+
+$20 Value buffers
+
+User block-fid
 
-create block-buffer chars/block chars allot
+: block-cold ( -- )
+    block-fid off  last-block off
+    buffer-struct buffers * %alloc dup block-buffers ! ( addr )
+    buffer-struct %size buffers * erase ;
 
-variable buffer-block 0 buffer-block ! \ the block currently in the buffer
-variable block-fid 0 block-fid ! \ the file id of the current block file
-variable buffer-dirty buffer-dirty off
+' block-cold INIT8 chained
 
+block-cold
 
-: get-block-fid ( -- fid )
+Defer flush-blocks
+
+: open-blocks ( addr u -- ) \ gforth
+    \g Use the file, whose name is given by @var{addr u}, as the blocks file.
+    2dup open-fpath-file 0<>
+    if
+	r/w bin create-file throw
+    else
+	rot close-file throw  2dup file-status throw bin open-file throw
+	>r 2drop r>
+    then
+    block-fid @ IF  flush-blocks block-fid @ close-file throw  THEN
+    block-fid ! ;
+
+: use ( "file" -- ) \ gforth
+    \g Use @var{file} as the blocks file.
+    name open-blocks ;
+
+\ the file is opened as binary file, since it either will contain text
+\ without newlines or binary data
+: get-block-fid ( -- fid ) \ gforth
     block-fid @ 0=
     if
-	s" blocks.fb" r/w open-file 0<>
-	if
-	    s" blocks.fb" r/w create-file .s throw
-	then
-	block-fid !
+	s" blocks.fb" open-blocks
     then
     block-fid @ ;
 
-: block-position ( u -- )
-    \ positions the block file to the start of block u
-    1- chars/block chars um* get-block-fid reposition-file .s throw ;
-
-: update ( -- )
-    buffer-dirty on ;
-
-: save-buffers ( -- )
-    buffer-dirty @
+: block-position ( u -- ) \ block
+    \G Position the block file to the start of block @var{u}.
+    1- chars/block chars um* get-block-fid reposition-file throw ;
+
+: update ( -- ) \ block
+    last-block @ ?dup IF  buffer-dirty on  THEN ;
+
+: save-buffer ( buffer -- ) \ gforth
+    >r
+    r@ buffer-dirty @ r@ buffer-block @ 0<> and
     if
-	buffer-block @ block-position
-	block-buffer chars/block get-block-fid write-file throw
-	buffer-dirty off
-    endif ;
-
-: empty-buffers ( -- )
-    0 buffer-block ! ;
+	r@ buffer-block @ block-position
+	r@ block-buffer chars/block  r@ buffer-fid @  write-file throw
+	r@ buffer-dirty off
+    endif
+    rdrop ;
+
+: empty-buffer ( buffer -- ) \ gforth
+    buffer-block off ;
+
+: save-buffers  ( -- ) \ block
+    block-buffers @
+    buffers 0 ?DO  dup save-buffer  next-buffer  LOOP  drop ;
+
+: empty-buffers ( -- ) \ block
+    block-buffers @
+    buffers 0 ?DO  dup empty-buffer  next-buffer  LOOP  drop ;
 
-: flush ( -- )
+: flush ( -- ) \ block
     save-buffers
     empty-buffers ;
 
-: block ( u -- a-addr )
+' flush IS flush-blocks
+
+: get-buffer ( n -- a-addr ) \ gforth
+    buffers mod buffer-struct %size * block-buffers @ + ;
+
+: block ( u -- a-addr ) \ block- block
+  \G @var{u} identifies a block number. Assign a block buffer to @var{u},
+  \G make it the current block buffer and return its start
+  \G address, @var{a-addr}.
     dup 0= -35 and throw
-    dup buffer-block @ <>
+    dup get-buffer >r
+    dup r@ buffer-block @ <>
+    r@ buffer-fid @ block-fid @ <> or
     if
-	save-buffers
+	r@ save-buffer
 	dup block-position
-	block-buffer chars/block get-block-fid read-file .s throw
+	r@ block-buffer chars/block get-block-fid read-file throw
 	\ clear the rest of the buffer if the file is too short
-	block-buffer over chars + chars/block rot - blank
-	buffer-block !    
+	r@ block-buffer over chars + chars/block rot chars - blank
+	r@ buffer-block !
+	get-block-fid r@ buffer-fid !
     else
 	drop
     then
-    block-buffer ;
+    r> dup last-block ! block-buffer ;
 
-: buffer ( u -- a-addr )
+: buffer ( u -- a-addr ) \ block
     \ reading in the block is unnecessary, but simpler
     block ;
 
-variable scr 0 scr ! \ !! this should be a user var
+User scr ( -- a-addr ) \ block-ext
+    \G USER VARIABLE @var{a-addr} is the address of a cell containing
+    \G the block number of the block most recently processed by
+    \G @code{LIST}.
+    0 scr !
+
+: updated?  ( n -- f ) \ gforth
+    scr @ buffer
+    [ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
 
-: list ( u -- )
+: list ( u -- ) \ block
     \ calling block again and again looks inefficient but is necessary
     \ in a multitasking environment
     dup scr !
-    ." Screen " u. cr
+    ." Screen " u.
+    updated?  0= IF ." not "  THEN  ." modified     " cr
     16 0
     ?do
-	scr @ block i 64 * chars + 64 type cr
+	i 2 .r space scr @ block i 64 * chars + 64 type cr
     loop ;
 
-
-\ not yet implemented (with block semantics):
-
-\ evaluate
-\ load
-\ refill
-\ thru
-\ \
+: (source)  ( -- c-addr u )
+  blk @ ?dup
+  IF    block chars/block
+  ELSE  tib #tib @
+  THEN ;
+
+' (source) IS source ( -- c-addr u ) \ core
+\G @var{c-addr} is the address of the input buffer and @var{u} is the
+\G number of characters in it.
+
+: load ( i*x n -- j*x ) \ block
+  push-file
+  dup loadline ! blk ! >in off ['] interpret catch
+  pop-file throw ;
+
+: thru ( i*x n1 n2 -- j*x ) \ block
+  1+ swap ?DO  I load  LOOP ;
+
+: +load ( i*x n -- j*x ) \ block
+    blk @ + load ;
+
+: +thru ( i*x n1 n2 -- j*x ) \ block
+  1+ swap ?DO  I +load  LOOP ;
+
+: --> ( -- ) \ block- block
+    \G If this symbol is encountered whilst loading block @var{n},
+    \G discard the remainder of the block and load block @var{n+1}. Used
+    \G for chaining multiple blocks together as a single loadable unit.
+    refill drop ; immediate
+
+: block-included ( addr u -- ) \ gforth
+    block-fid @ >r block-fid off open-blocks
+    1 load block-fid @ close-file throw flush
+    r> block-fid ! ;
+
+\ thrown out because it may provide unpleasant surprises - anton
+\ : include ( "name" -- )
+\     name 2dup dup 3 - /string s" .fb" compare
+\     0= IF  block-included  ELSE  included  THEN ;
+
+get-current environment-wordlist set-current
+true constant block
+true constant block-ext
+set-current
+
+: bye ( -- ) \ tools-ext
+  \G Return control to the host operating system (if any).
+  ['] flush catch drop bye ;