Annotation of gforth/blocks.fs, revision 1.24

1.5       pazsan      1: \ A less simple implementation of the blocks wordset. 
1.1       anton       2: 
1.19      anton       3: \ Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
1.7       anton       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
1.17      anton      35:     cell%              field buffer-block   \ the block number
                     36:     cell%              field buffer-fid     \ the block's fid
                     37:     cell%              field buffer-dirty   \ the block dirty flag
                     38:     char% chars/block * field block-buffer   \ the data
                     39:     cell% 0 *          field next-buffer
1.5       pazsan     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: 
1.17      anton      49: : block-cold ( -- )
1.16      jwilke     50:     block-fid off  last-block off
1.17      anton      51:     buffer-struct buffers * %alloc dup block-buffers ! ( addr )
                     52:     buffer-struct %size buffers * erase ;
1.1       anton      53: 
1.16      jwilke     54: ' block-cold INIT8 chained
1.5       pazsan     55: 
                     56: block-cold
                     57: 
1.24    ! crook      58: Defer flush-blocks ( -- ) \ gforth
1.5       pazsan     59: 
1.24    ! crook      60: : open-blocks ( c-addr u -- ) \ gforth
        !            61:     \g Use the file, whose name is given by @i{c-addr u}, as the blocks file.
1.18      pazsan     62:     2dup open-fpath-file 0<>
1.5       pazsan     63:     if
1.18      pazsan     64:        r/w bin create-file throw
1.5       pazsan     65:     else
1.8       pazsan     66:        rot close-file throw  2dup file-status throw bin open-file throw
                     67:        >r 2drop r>
1.5       pazsan     68:     then
1.12      anton      69:     block-fid @ IF  flush-blocks block-fid @ close-file throw  THEN
1.5       pazsan     70:     block-fid ! ;
1.8       pazsan     71: 
1.10      anton      72: : use ( "file" -- ) \ gforth
1.24    ! crook      73:     \g Use @i{file} as the blocks file.
1.11      anton      74:     name open-blocks ;
1.1       anton      75: 
1.3       anton      76: \ the file is opened as binary file, since it either will contain text
                     77: \ without newlines or binary data
1.24    ! crook      78: : get-block-fid ( -- wfileid ) \ gforth
        !            79:     \G Return the file-id of the current blocks file. If no blocks
        !            80:     \G file has been opened, use @file{blocks.fb} as the default
        !            81:     \G blocks file.
1.1       anton      82:     block-fid @ 0=
                     83:     if
1.11      anton      84:        s" blocks.fb" open-blocks
1.1       anton      85:     then
                     86:     block-fid @ ;
                     87: 
1.20      pazsan     88: : block-position ( u -- ) \ block
1.24    ! crook      89:     \G Position the block file to the start of block @i{u}.
1.3       anton      90:     1- chars/block chars um* get-block-fid reposition-file throw ;
1.1       anton      91: 
1.20      pazsan     92: : update ( -- ) \ block
1.24    ! crook      93:     \G Mark the current block buffer as dirty.
1.5       pazsan     94:     last-block @ ?dup IF  buffer-dirty on  THEN ;
1.1       anton      95: 
1.20      pazsan     96: : save-buffer ( buffer -- ) \ gforth
                     97:     >r
1.5       pazsan     98:     r@ buffer-dirty @ r@ buffer-block @ 0<> and
1.1       anton      99:     if
1.5       pazsan    100:        r@ buffer-block @ block-position
                    101:        r@ block-buffer chars/block  r@ buffer-fid @  write-file throw
                    102:        r@ buffer-dirty off
                    103:     endif
                    104:     rdrop ;
                    105: 
1.20      pazsan    106: : empty-buffer ( buffer -- ) \ gforth
1.5       pazsan    107:     buffer-block off ;
                    108: 
1.20      pazsan    109: : save-buffers  ( -- ) \ block
1.24    ! crook     110:     \G Transfer the contents of each @code{update}d block buffer to
        !           111:     \G mass storage, then mark all block buffers as unassigned.
1.20      pazsan    112:     block-buffers @
1.24    ! crook     113:     buffers 0 ?DO dup save-buffer next-buffer LOOP drop ;
1.1       anton     114: 
1.24    ! crook     115: : empty-buffers ( -- ) \ block-ext
        !           116:     \G Mark all block buffers as unassigned; if any had been marked as
        !           117:     \G assigned-dirty (by @code{update}), the changes to those blocks
        !           118:     \G will be lost.
1.20      pazsan    119:     block-buffers @
1.24    ! crook     120:     buffers 0 ?DO dup empty-buffer next-buffer LOOP drop ;
1.1       anton     121: 
1.20      pazsan    122: : flush ( -- ) \ block
1.24    ! crook     123:     \G Perform the functions of @code{save-buffers} then
        !           124:     \G @code{empty-buffers}.
1.1       anton     125:     save-buffers
                    126:     empty-buffers ;
                    127: 
1.12      anton     128: ' flush IS flush-blocks
1.5       pazsan    129: 
1.20      pazsan    130: : get-buffer ( n -- a-addr ) \ gforth
1.17      anton     131:     buffers mod buffer-struct %size * block-buffers @ + ;
1.5       pazsan    132: 
1.21      crook     133: : block ( u -- a-addr ) \ block- block
1.24    ! crook     134:     \G If a block buffer is assigned for block @i{u}, return its
        !           135:     \G start address, @i{a-addr}. Otherwise, assign a block buffer
        !           136:     \G for block @i{u} (if the assigned block buffer has been
        !           137:     \G @code{update}d, transfer the contents to mass storage), read
        !           138:     \G the block into the block buffer and return its start address,
        !           139:     \G @i{a-addr}.
1.1       anton     140:     dup 0= -35 and throw
1.5       pazsan    141:     dup get-buffer >r
                    142:     dup r@ buffer-block @ <>
1.9       pazsan    143:     r@ buffer-fid @ block-fid @ <> or
1.1       anton     144:     if
1.5       pazsan    145:        r@ save-buffer
1.1       anton     146:        dup block-position
1.5       pazsan    147:        r@ block-buffer chars/block get-block-fid read-file throw
1.1       anton     148:        \ clear the rest of the buffer if the file is too short
1.5       pazsan    149:        r@ block-buffer over chars + chars/block rot chars - blank
                    150:        r@ buffer-block !
                    151:        get-block-fid r@ buffer-fid !
1.1       anton     152:     else
                    153:        drop
                    154:     then
1.5       pazsan    155:     r> dup last-block ! block-buffer ;
1.1       anton     156: 
1.20      pazsan    157: : buffer ( u -- a-addr ) \ block
1.24    ! crook     158:     \G If a block buffer is assigned for block @i{u}, return its
        !           159:     \G start address, @i{a-addr}. Otherwise, assign a block buffer
        !           160:     \G for block @i{u} (if the assigned block buffer has been
        !           161:     \G @code{update}d, transfer the contents to mass storage) and
        !           162:     \G return its start address, @i{a-addr}.  The subtle difference
        !           163:     \G between @code{buffer} and @code{block} mean that you should
        !           164:     \G only use @code{buffer} if you don't care about the previous
        !           165:     \G contents of block @i{u}. In Gforth, this simply calls
        !           166:     \G @code{block}.
1.1       anton     167:     \ reading in the block is unnecessary, but simpler
                    168:     block ;
                    169: 
1.21      crook     170: User scr ( -- a-addr ) \ block-ext
1.24    ! crook     171:     \G USER VARIABLE: @i{a-addr} is the address of a cell containing
1.21      crook     172:     \G the block number of the block most recently processed by
1.24    ! crook     173:     \G @code{list}.
        !           174: 0 scr !
1.1       anton     175: 
1.24    ! crook     176: \ nac31Mar1999 moved "scr @" to list to make the stack comment correct
1.20      pazsan    177: : updated?  ( n -- f ) \ gforth
1.24    ! crook     178:     \G Return true if block @i{n} has been marked as dirty.
        !           179:     buffer
1.5       pazsan    180:     [ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
                    181: 
1.24    ! crook     182: : list ( u -- ) \ block-ext
        !           183:     \G Display block @i{u}. In Gforth, the block is displayed as 16
        !           184:     \G numbered lines, each of 64 characters.
1.1       anton     185:     \ calling block again and again looks inefficient but is necessary
                    186:     \ in a multitasking environment
                    187:     dup scr !
1.5       pazsan    188:     ." Screen " u.
1.24    ! crook     189:     scr @ updated?  0= IF ." not "  THEN  ." modified     " cr
1.1       anton     190:     16 0
                    191:     ?do
1.4       anton     192:        i 2 .r space scr @ block i 64 * chars + 64 type cr
1.1       anton     193:     loop ;
                    194: 
1.23      crook     195: : (source)  ( -- c-addr u )
1.2       pazsan    196:   blk @ ?dup
                    197:   IF    block chars/block
                    198:   ELSE  tib #tib @
                    199:   THEN ;
                    200: 
1.23      crook     201: ' (source) IS source ( -- c-addr u ) \ core
1.24    ! crook     202: \G @i{c-addr} is the address of the input buffer and @i{u} is the
1.23      crook     203: \G number of characters in it.
1.2       pazsan    204: 
1.20      pazsan    205: : load ( i*x n -- j*x ) \ block
1.24    ! crook     206:     \G Save the current input source specification. Store @i{n} in
        !           207:     \G @code{BLK}, set @code{>IN} to 0 and interpret. When the parse
        !           208:     \G area is exhausted, restore the input source specification.
        !           209:     push-file
        !           210:     dup loadline ! blk ! >in off ['] interpret catch
        !           211:     pop-file throw ;
        !           212: 
        !           213: : thru ( i*x n1 n2 -- j*x ) \ block-ext
        !           214:     \G @code{load} the blocks @i{n1} through @i{n2} in sequence.
        !           215:     1+ swap ?DO  I load  LOOP ;
        !           216: 
        !           217: : +load ( i*x n -- j*x ) \ gforth
        !           218:     \G Used within a block to load the block specified as the
        !           219:     \G current block + @i{n}.
1.20      pazsan    220:     blk @ + load ;
1.2       pazsan    221: 
1.24    ! crook     222: : +thru ( i*x n1 n2 -- j*x ) \ gforth
        !           223:     \G Used within a block to load the range of blocks specified as the
        !           224:     \G current block + @i{n1} thru the current block + @i{n2}.
        !           225:     1+ swap ?DO  I +load  LOOP ;
        !           226: 
        !           227: : --> ( -- ) \ block- block chain
        !           228:     \G If this symbol is encountered whilst loading block @i{n},
        !           229:     \G discard the remainder of the block and load block @i{n+1}. Used
1.21      crook     230:     \G for chaining multiple blocks together as a single loadable unit.
1.20      pazsan    231:     refill drop ; immediate
1.5       pazsan    232: 
1.24    ! crook     233: : block-included ( a-addr u -- ) \ gforth
        !           234:     \G Use within a block that is to be processed by @code{load}. Save
        !           235:     \G the current blocks file specification, open the blocks file
        !           236:     \G specified by @i{a-addr u} and @code{load} block 1 from that
        !           237:     \G file (which may in turn chain or load other blocks). Finally,
        !           238:     \G close the blocks file and restore the original blocks file.
1.11      anton     239:     block-fid @ >r block-fid off open-blocks
1.5       pazsan    240:     1 load block-fid @ close-file throw flush
                    241:     r> block-fid ! ;
                    242: 
1.13      anton     243: \ thrown out because it may provide unpleasant surprises - anton
                    244: \ : include ( "name" -- )
                    245: \     name 2dup dup 3 - /string s" .fb" compare
                    246: \     0= IF  block-included  ELSE  included  THEN ;
1.5       pazsan    247: 
1.4       anton     248: get-current environment-wordlist set-current
                    249: true constant block
                    250: true constant block-ext
                    251: set-current
1.5       pazsan    252: 
1.21      crook     253: : bye ( -- ) \ tools-ext
                    254:   \G Return control to the host operating system (if any).
                    255:   ['] flush catch drop bye ;

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