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Annotation of gforth/blocks.fs, revision 1.7

1.5       pazsan      1: \ A less simple implementation of the blocks wordset. 
1.1       anton       2: 
1.7     ! anton       3: \ Copyright (C) 1995 Free Software Foundation, Inc.
        !             4: 
        !             5: \ This file is part of Gforth.
        !             6: 
        !             7: \ Gforth is free software; you can redistribute it and/or
        !             8: \ modify it under the terms of the GNU General Public License
        !             9: \ as published by the Free Software Foundation; either version 2
        !            10: \ of the License, or (at your option) any later version.
        !            11: 
        !            12: \ This program is distributed in the hope that it will be useful,
        !            13: \ but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            14: \ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            15: \ GNU General Public License for more details.
        !            16: 
        !            17: \ You should have received a copy of the GNU General Public License
        !            18: \ along with this program; if not, write to the Free Software
        !            19: \ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            20: 
        !            21: 
        !            22: \ A more efficient implementation would use mmap on OSs that
1.1       anton      23: \ provide it and many buffers on OSs that do not provide mmap.
                     24: 
1.5       pazsan     25: \ Now, the replacement algorithm is "direct mapped"; change to LRU
                     26: \ if too slow. Using more buffers helps, too.
                     27: 
1.1       anton      28: \ I think I avoid the assumption 1 char = 1 here, but I have not tested this
                     29: 
1.2       pazsan     30: \ 1024 constant chars/block \ mandated by the standard
1.1       anton      31: 
1.5       pazsan     32: require struct.fs
                     33: 
                     34: struct
                     35:     1           cells: field buffer-block   \ the block number
                     36:     1           cells: field buffer-fid     \ the block's fid
                     37:     1           cells: field buffer-dirty   \ the block dirty flag
                     38:     chars/block chars: field block-buffer   \ the data
                     39:     0           cells: field next-buffer
                     40: end-struct buffer-struct
                     41: 
                     42: Variable block-buffers
                     43: Variable last-block
                     44: 
                     45: $20 Value buffers
                     46: 
                     47: User block-fid
1.1       anton      48: 
1.5       pazsan     49: : block-cold
                     50:     defers 'cold  block-fid off  last-block off
                     51:     buffers buffer-struct drop * allocate throw dup block-buffers !
                     52:     buffers buffer-struct drop * erase ;
1.1       anton      53: 
1.5       pazsan     54: ' block-cold IS 'cold
                     55: 
                     56: block-cold
                     57: 
                     58: Defer flush-file
                     59: 
                     60: : use-file ( addr u -- )
                     61:     2dup r/w bin open-file 0<>
                     62:     if
                     63:        drop r/w bin create-file throw
                     64:     else
                     65:        nip nip
                     66:     then
1.6       pazsan     67:     block-fid @ IF  flush-file block-fid @ close-file throw  THEN
1.5       pazsan     68:     block-fid ! ;
1.1       anton      69: 
1.3       anton      70: \ the file is opened as binary file, since it either will contain text
                     71: \ without newlines or binary data
1.1       anton      72: : get-block-fid ( -- fid )
                     73:     block-fid @ 0=
                     74:     if
1.5       pazsan     75:        s" blocks.fb" use-file
1.1       anton      76:     then
                     77:     block-fid @ ;
                     78: 
                     79: : block-position ( u -- )
                     80:     \ positions the block file to the start of block u
1.3       anton      81:     1- chars/block chars um* get-block-fid reposition-file throw ;
1.1       anton      82: 
                     83: : update ( -- )
1.5       pazsan     84:     last-block @ ?dup IF  buffer-dirty on  THEN ;
1.1       anton      85: 
1.5       pazsan     86: : save-buffer ( buffer -- ) >r
                     87:     r@ buffer-dirty @ r@ buffer-block @ 0<> and
1.1       anton      88:     if
1.5       pazsan     89:        r@ buffer-block @ block-position
                     90:        r@ block-buffer chars/block  r@ buffer-fid @  write-file throw
                     91:        r@ buffer-dirty off
                     92:     endif
                     93:     rdrop ;
                     94: 
                     95: : empty-buffer ( buffer -- )
                     96:     buffer-block off ;
                     97: 
                     98: : save-buffers  ( -- )    block-buffers @
                     99:     buffers 0 ?DO  dup save-buffer  next-buffer  LOOP  drop ;
1.1       anton     100: 
1.5       pazsan    101: : empty-buffers ( -- )    block-buffers @
                    102:     buffers 0 ?DO  dup empty-buffer  next-buffer  LOOP  drop ;
1.1       anton     103: 
                    104: : flush ( -- )
                    105:     save-buffers
                    106:     empty-buffers ;
                    107: 
1.5       pazsan    108: ' flush IS flush-file
                    109: 
                    110: : get-buffer ( n -- a-addr )
                    111:     buffers mod buffer-struct drop * block-buffers @ + ;
                    112: 
1.1       anton     113: : block ( u -- a-addr )
                    114:     dup 0= -35 and throw
1.5       pazsan    115:     dup get-buffer >r
                    116:     dup r@ buffer-block @ <>
                    117:     r@ buffer-fid @ block-fid @ <> and
1.1       anton     118:     if
1.5       pazsan    119:        r@ save-buffer
1.1       anton     120:        dup block-position
1.5       pazsan    121:        r@ block-buffer chars/block get-block-fid read-file throw
1.1       anton     122:        \ clear the rest of the buffer if the file is too short
1.5       pazsan    123:        r@ block-buffer over chars + chars/block rot chars - blank
                    124:        r@ buffer-block !
                    125:        get-block-fid r@ buffer-fid !
1.1       anton     126:     else
                    127:        drop
                    128:     then
1.5       pazsan    129:     r> dup last-block ! block-buffer ;
1.1       anton     130: 
                    131: : buffer ( u -- a-addr )
                    132:     \ reading in the block is unnecessary, but simpler
                    133:     block ;
                    134: 
1.2       pazsan    135: User scr 0 scr !
1.1       anton     136: 
1.5       pazsan    137: : updated?  ( n -- f )   scr @ buffer
                    138:     [ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
                    139: 
1.1       anton     140: : list ( u -- )
                    141:     \ calling block again and again looks inefficient but is necessary
                    142:     \ in a multitasking environment
                    143:     dup scr !
1.5       pazsan    144:     ." Screen " u.
                    145:     updated?  0= IF ." not "  THEN  ." modified     " cr
1.1       anton     146:     16 0
                    147:     ?do
1.4       anton     148:        i 2 .r space scr @ block i 64 * chars + 64 type cr
1.1       anton     149:     loop ;
                    150: 
1.2       pazsan    151: : (source)  ( -- addr len )
                    152:   blk @ ?dup
                    153:   IF    block chars/block
                    154:   ELSE  tib #tib @
                    155:   THEN ;
                    156: 
                    157: ' (source) IS source
                    158: 
                    159: : load ( i*x n -- j*x )
                    160:   push-file
                    161:   dup loadline ! blk ! >in off ( ['] ) interpret ( catch )
                    162:   pop-file ( throw ) ;
1.1       anton     163: 
1.2       pazsan    164: : thru ( i*x n1 n2 -- j*x )
                    165:   1+ swap 0 ?DO  I load  LOOP ;
1.1       anton     166: 
1.2       pazsan    167: : +load ( i*x n -- j*x )  blk @ + load ;
                    168: 
                    169: : +thru ( i*x n1 n2 -- j*x )
                    170:   1+ swap 0 ?DO  I +load  LOOP ;
1.4       anton     171: 
1.5       pazsan    172: : --> ( -- )  refill drop ; immediate
                    173: 
                    174: : block-included ( addr u -- )
                    175:     block-fid @ >r block-fid off use-file
                    176:     1 load block-fid @ close-file throw flush
                    177:     r> block-fid ! ;
                    178: 
                    179: : include ( "name" -- )
                    180:     name 2dup dup 3 - /string s" .fb" compare
                    181:     0= IF  block-included  ELSE  included  THEN ;
                    182: 
1.4       anton     183: get-current environment-wordlist set-current
                    184: true constant block
                    185: true constant block-ext
                    186: set-current
1.5       pazsan    187: 
                    188: : bye  ['] flush catch drop bye ;