Annotation of gforth/blocks.fs, revision 1.28

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
1.26      pazsan     48: User offset   0 offset !  \ store 1 here fore 0.4.0 compatibility
1.1       anton      49: 
1.17      anton      50: : block-cold ( -- )
1.16      jwilke     51:     block-fid off  last-block off
1.17      anton      52:     buffer-struct buffers * %alloc dup block-buffers ! ( addr )
                     53:     buffer-struct %size buffers * erase ;
1.1       anton      54: 
1.16      jwilke     55: ' block-cold INIT8 chained
1.5       pazsan     56: 
                     57: block-cold
                     58: 
1.24      crook      59: Defer flush-blocks ( -- ) \ gforth
1.5       pazsan     60: 
1.24      crook      61: : open-blocks ( c-addr u -- ) \ gforth
                     62:     \g Use the file, whose name is given by @i{c-addr u}, as the blocks file.
1.18      pazsan     63:     2dup open-fpath-file 0<>
1.5       pazsan     64:     if
1.18      pazsan     65:        r/w bin create-file throw
1.5       pazsan     66:     else
1.8       pazsan     67:        rot close-file throw  2dup file-status throw bin open-file throw
                     68:        >r 2drop r>
1.5       pazsan     69:     then
1.12      anton      70:     block-fid @ IF  flush-blocks block-fid @ close-file throw  THEN
1.5       pazsan     71:     block-fid ! ;
1.8       pazsan     72: 
1.10      anton      73: : use ( "file" -- ) \ gforth
1.24      crook      74:     \g Use @i{file} as the blocks file.
1.11      anton      75:     name open-blocks ;
1.1       anton      76: 
1.3       anton      77: \ the file is opened as binary file, since it either will contain text
                     78: \ without newlines or binary data
1.24      crook      79: : get-block-fid ( -- wfileid ) \ gforth
                     80:     \G Return the file-id of the current blocks file. If no blocks
                     81:     \G file has been opened, use @file{blocks.fb} as the default
                     82:     \G blocks file.
1.1       anton      83:     block-fid @ 0=
                     84:     if
1.11      anton      85:        s" blocks.fb" open-blocks
1.1       anton      86:     then
                     87:     block-fid @ ;
                     88: 
1.20      pazsan     89: : block-position ( u -- ) \ block
1.24      crook      90:     \G Position the block file to the start of block @i{u}.
1.26      pazsan     91:     offset @ - chars/block chars um* get-block-fid reposition-file throw ;
1.1       anton      92: 
1.20      pazsan     93: : update ( -- ) \ block
1.24      crook      94:     \G Mark the current block buffer as dirty.
1.5       pazsan     95:     last-block @ ?dup IF  buffer-dirty on  THEN ;
1.1       anton      96: 
1.20      pazsan     97: : save-buffer ( buffer -- ) \ gforth
                     98:     >r
1.5       pazsan     99:     r@ buffer-dirty @ r@ buffer-block @ 0<> and
1.1       anton     100:     if
1.5       pazsan    101:        r@ buffer-block @ block-position
                    102:        r@ block-buffer chars/block  r@ buffer-fid @  write-file throw
                    103:        r@ buffer-dirty off
                    104:     endif
                    105:     rdrop ;
                    106: 
1.20      pazsan    107: : empty-buffer ( buffer -- ) \ gforth
1.5       pazsan    108:     buffer-block off ;
                    109: 
1.20      pazsan    110: : save-buffers  ( -- ) \ block
1.24      crook     111:     \G Transfer the contents of each @code{update}d block buffer to
                    112:     \G mass storage, then mark all block buffers as unassigned.
1.20      pazsan    113:     block-buffers @
1.24      crook     114:     buffers 0 ?DO dup save-buffer next-buffer LOOP drop ;
1.1       anton     115: 
1.24      crook     116: : empty-buffers ( -- ) \ block-ext
                    117:     \G Mark all block buffers as unassigned; if any had been marked as
                    118:     \G assigned-dirty (by @code{update}), the changes to those blocks
                    119:     \G will be lost.
1.20      pazsan    120:     block-buffers @
1.24      crook     121:     buffers 0 ?DO dup empty-buffer next-buffer LOOP drop ;
1.1       anton     122: 
1.20      pazsan    123: : flush ( -- ) \ block
1.24      crook     124:     \G Perform the functions of @code{save-buffers} then
                    125:     \G @code{empty-buffers}.
1.1       anton     126:     save-buffers
                    127:     empty-buffers ;
                    128: 
1.12      anton     129: ' flush IS flush-blocks
1.5       pazsan    130: 
1.26      pazsan    131: : get-buffer ( u -- a-addr ) \ gforth
                    132:     0 buffers um/mod drop buffer-struct %size * block-buffers @ + ;
1.5       pazsan    133: 
1.28    ! crook     134: : block ( u -- a-addr ) \ gforthman- block
1.24      crook     135:     \G If a block buffer is assigned for block @i{u}, return its
                    136:     \G start address, @i{a-addr}. Otherwise, assign a block buffer
                    137:     \G for block @i{u} (if the assigned block buffer has been
                    138:     \G @code{update}d, transfer the contents to mass storage), read
                    139:     \G the block into the block buffer and return its start address,
                    140:     \G @i{a-addr}.
1.26      pazsan    141:     dup offset @ u< -35 and throw
1.5       pazsan    142:     dup get-buffer >r
                    143:     dup r@ buffer-block @ <>
1.9       pazsan    144:     r@ buffer-fid @ block-fid @ <> or
1.1       anton     145:     if
1.5       pazsan    146:        r@ save-buffer
1.1       anton     147:        dup block-position
1.5       pazsan    148:        r@ block-buffer chars/block get-block-fid read-file throw
1.1       anton     149:        \ clear the rest of the buffer if the file is too short
1.5       pazsan    150:        r@ block-buffer over chars + chars/block rot chars - blank
                    151:        r@ buffer-block !
                    152:        get-block-fid r@ buffer-fid !
1.1       anton     153:     else
                    154:        drop
                    155:     then
1.5       pazsan    156:     r> dup last-block ! block-buffer ;
1.1       anton     157: 
1.20      pazsan    158: : buffer ( u -- a-addr ) \ block
1.24      crook     159:     \G If a block buffer is assigned for block @i{u}, return its
                    160:     \G start address, @i{a-addr}. Otherwise, assign a block buffer
                    161:     \G for block @i{u} (if the assigned block buffer has been
                    162:     \G @code{update}d, transfer the contents to mass storage) and
                    163:     \G return its start address, @i{a-addr}.  The subtle difference
                    164:     \G between @code{buffer} and @code{block} mean that you should
                    165:     \G only use @code{buffer} if you don't care about the previous
                    166:     \G contents of block @i{u}. In Gforth, this simply calls
                    167:     \G @code{block}.
1.1       anton     168:     \ reading in the block is unnecessary, but simpler
                    169:     block ;
                    170: 
1.28    ! crook     171: User scr ( -- a-addr ) \ block-ext s-c-r
1.27      crook     172:     \G @code{User} variable -- @i{a-addr} is the address of a cell containing
1.21      crook     173:     \G the block number of the block most recently processed by
1.24      crook     174:     \G @code{list}.
                    175: 0 scr !
1.1       anton     176: 
1.24      crook     177: \ nac31Mar1999 moved "scr @" to list to make the stack comment correct
1.20      pazsan    178: : updated?  ( n -- f ) \ gforth
1.24      crook     179:     \G Return true if block @i{n} has been marked as dirty.
                    180:     buffer
1.5       pazsan    181:     [ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
                    182: 
1.24      crook     183: : list ( u -- ) \ block-ext
                    184:     \G Display block @i{u}. In Gforth, the block is displayed as 16
                    185:     \G numbered lines, each of 64 characters.
1.1       anton     186:     \ calling block again and again looks inefficient but is necessary
                    187:     \ in a multitasking environment
                    188:     dup scr !
1.5       pazsan    189:     ." Screen " u.
1.24      crook     190:     scr @ updated?  0= IF ." not "  THEN  ." modified     " cr
1.1       anton     191:     16 0
                    192:     ?do
1.4       anton     193:        i 2 .r space scr @ block i 64 * chars + 64 type cr
1.1       anton     194:     loop ;
                    195: 
1.23      crook     196: : (source)  ( -- c-addr u )
1.2       pazsan    197:   blk @ ?dup
                    198:   IF    block chars/block
                    199:   ELSE  tib #tib @
                    200:   THEN ;
                    201: 
1.23      crook     202: ' (source) IS source ( -- c-addr u ) \ core
1.24      crook     203: \G @i{c-addr} is the address of the input buffer and @i{u} is the
1.23      crook     204: \G number of characters in it.
1.2       pazsan    205: 
1.20      pazsan    206: : load ( i*x n -- j*x ) \ block
1.24      crook     207:     \G Save the current input source specification. Store @i{n} in
                    208:     \G @code{BLK}, set @code{>IN} to 0 and interpret. When the parse
                    209:     \G area is exhausted, restore the input source specification.
                    210:     push-file
                    211:     dup loadline ! blk ! >in off ['] interpret catch
                    212:     pop-file throw ;
                    213: 
                    214: : thru ( i*x n1 n2 -- j*x ) \ block-ext
                    215:     \G @code{load} the blocks @i{n1} through @i{n2} in sequence.
                    216:     1+ swap ?DO  I load  LOOP ;
                    217: 
                    218: : +load ( i*x n -- j*x ) \ gforth
                    219:     \G Used within a block to load the block specified as the
                    220:     \G current block + @i{n}.
1.20      pazsan    221:     blk @ + load ;
1.2       pazsan    222: 
1.24      crook     223: : +thru ( i*x n1 n2 -- j*x ) \ gforth
                    224:     \G Used within a block to load the range of blocks specified as the
                    225:     \G current block + @i{n1} thru the current block + @i{n2}.
                    226:     1+ swap ?DO  I +load  LOOP ;
                    227: 
1.28    ! crook     228: : --> ( -- ) \ gforthman- gforth chain
1.24      crook     229:     \G If this symbol is encountered whilst loading block @i{n},
                    230:     \G discard the remainder of the block and load block @i{n+1}. Used
1.25      anton     231:     \G for chaining multiple blocks together as a single loadable
                    232:     \G unit.  Not recommended, because it destroys the independence of
                    233:     \G loading.  Use @code{thru} (which is standard) or @code{+thru}
                    234:     \G instead.
1.20      pazsan    235:     refill drop ; immediate
1.5       pazsan    236: 
1.24      crook     237: : block-included ( a-addr u -- ) \ gforth
                    238:     \G Use within a block that is to be processed by @code{load}. Save
                    239:     \G the current blocks file specification, open the blocks file
                    240:     \G specified by @i{a-addr u} and @code{load} block 1 from that
                    241:     \G file (which may in turn chain or load other blocks). Finally,
                    242:     \G close the blocks file and restore the original blocks file.
1.11      anton     243:     block-fid @ >r block-fid off open-blocks
1.5       pazsan    244:     1 load block-fid @ close-file throw flush
                    245:     r> block-fid ! ;
                    246: 
1.13      anton     247: \ thrown out because it may provide unpleasant surprises - anton
                    248: \ : include ( "name" -- )
                    249: \     name 2dup dup 3 - /string s" .fb" compare
                    250: \     0= IF  block-included  ELSE  included  THEN ;
1.5       pazsan    251: 
1.4       anton     252: get-current environment-wordlist set-current
                    253: true constant block
                    254: true constant block-ext
                    255: set-current
1.5       pazsan    256: 
1.21      crook     257: : bye ( -- ) \ tools-ext
                    258:   \G Return control to the host operating system (if any).
                    259:   ['] flush catch drop bye ;

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