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Annotation of gforth/blocks.fs, revision 1.6

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