\ A less simple implementation of the blocks wordset.
\ Copyright (C) 1995 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
1 cells: field buffer-block \ the block number
1 cells: field buffer-fid \ the block's fid
1 cells: field buffer-dirty \ the block dirty flag
chars/block chars: field block-buffer \ the data
0 cells: field next-buffer
$20 Value buffers
defers 'cold block-fid off last-block off
buffers buffer-struct drop * allocate throw dup block-buffers !
buffers buffer-struct drop * erase ;
' block-cold IS 'cold
: use-file ( addr u -- )
2dup r/w bin open-file 0<>
drop r/w bin create-file throw
block-fid @ IF flush-file block-fid @ close-file throw THEN
block-fid ! ;
\ the file is opened as binary file, since it either will contain text
\ without newlines or binary data
: get-block-fid ( -- fid )
block-fid @ 0=
s" blocks.fb" use-file
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 throw ;
: update ( -- )
last-block @ ?dup IF buffer-dirty on THEN ;
: save-buffer ( buffer -- ) >r
r@ buffer-dirty @ r@ buffer-block @ 0<> and
r@ buffer-block @ block-position
r@ block-buffer chars/block r@ buffer-fid @ write-file throw
r@ buffer-dirty off
: empty-buffer ( buffer -- )
buffer-block off ;
: save-buffers ( -- ) block-buffers @
buffers 0 ?DO dup save-buffer next-buffer LOOP drop ;
: empty-buffers ( -- ) block-buffers @
buffers 0 ?DO dup empty-buffer next-buffer LOOP drop ;
: flush ( -- )
' flush IS flush-file
: get-buffer ( n -- a-addr )
buffers mod buffer-struct drop * block-buffers @ + ;
: block ( u -- a-addr )
dup 0= -35 and throw
dup get-buffer >r
dup r@ buffer-block @ <>
r@ buffer-fid @ block-fid @ <> and
r@ block-buffer chars/block get-block-fid read-file throw
\ clear the rest of the buffer if the file is too short
r@ block-buffer over chars + chars/block rot chars - blank
r@ buffer-block !
get-block-fid r@ buffer-fid !
r> dup last-block ! block-buffer ;
: buffer ( u -- a-addr )
\ reading in the block is unnecessary, but simpler
User scr 0 scr !
: updated? ( n -- f ) scr @ buffer
[ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
: list ( u -- )
\ calling block again and again looks inefficient but is necessary
\ in a multitasking environment
dup scr !
." Screen " u.
updated? 0= IF ." not " THEN ." modified " cr
i 2 .r space scr @ block i 64 * chars + 64 type cr
: (source) ( -- addr len )
blk @ ?dup
IF block chars/block
ELSE tib #tib @
' (source) IS source
: load ( i*x n -- j*x )
dup loadline ! blk ! >in off ( ['] ) interpret ( catch )
pop-file ( throw ) ;
: thru ( i*x n1 n2 -- j*x )
1+ swap 0 ?DO I load LOOP ;
: +load ( i*x n -- j*x ) blk @ + load ;
: +thru ( i*x n1 n2 -- j*x )
1+ swap 0 ?DO I +load LOOP ;
: --> ( -- ) refill drop ; immediate
: block-included ( addr u -- )
block-fid @ >r block-fid off use-file
1 load block-fid @ close-file throw flush
r> block-fid ! ;
: 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
: bye ['] flush catch drop bye ;