Annotation of gforth/blocks.fs, revision 1.31

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
1.30      anton      48: User block-offset ( -- addr ) \ gforth
                     49: \G User variable containing the number of the first block (default
                     50: \G since 0.5.0: 0).  Block files created with Gforth versions before
                     51: \G 0.5.0 have the offset 1.  If you use these files you can: @code{1
                     52: \G offset !}; or add 1 to every block number used; or prepend 1024
                     53: \G characters to the file.
                     54: 0 block-offset !  \ store 1 here fore 0.4.0 compatibility
                     55: 
                     56: ' block-offset alias offset \ !! eliminate this?
1.1       anton      57: 
1.17      anton      58: : block-cold ( -- )
1.16      jwilke     59:     block-fid off  last-block off
1.17      anton      60:     buffer-struct buffers * %alloc dup block-buffers ! ( addr )
                     61:     buffer-struct %size buffers * erase ;
1.1       anton      62: 
1.16      jwilke     63: ' block-cold INIT8 chained
1.5       pazsan     64: 
                     65: block-cold
                     66: 
1.24      crook      67: Defer flush-blocks ( -- ) \ gforth
1.5       pazsan     68: 
1.24      crook      69: : open-blocks ( c-addr u -- ) \ gforth
                     70:     \g Use the file, whose name is given by @i{c-addr u}, as the blocks file.
1.18      pazsan     71:     2dup open-fpath-file 0<>
1.5       pazsan     72:     if
1.18      pazsan     73:        r/w bin create-file throw
1.5       pazsan     74:     else
1.8       pazsan     75:        rot close-file throw  2dup file-status throw bin open-file throw
                     76:        >r 2drop r>
1.5       pazsan     77:     then
1.12      anton      78:     block-fid @ IF  flush-blocks block-fid @ close-file throw  THEN
1.5       pazsan     79:     block-fid ! ;
1.8       pazsan     80: 
1.10      anton      81: : use ( "file" -- ) \ gforth
1.24      crook      82:     \g Use @i{file} as the blocks file.
1.11      anton      83:     name open-blocks ;
1.1       anton      84: 
1.3       anton      85: \ the file is opened as binary file, since it either will contain text
                     86: \ without newlines or binary data
1.24      crook      87: : get-block-fid ( -- wfileid ) \ gforth
                     88:     \G Return the file-id of the current blocks file. If no blocks
                     89:     \G file has been opened, use @file{blocks.fb} as the default
                     90:     \G blocks file.
1.1       anton      91:     block-fid @ 0=
                     92:     if
1.11      anton      93:        s" blocks.fb" open-blocks
1.1       anton      94:     then
                     95:     block-fid @ ;
                     96: 
1.20      pazsan     97: : block-position ( u -- ) \ block
1.24      crook      98:     \G Position the block file to the start of block @i{u}.
1.26      pazsan     99:     offset @ - chars/block chars um* get-block-fid reposition-file throw ;
1.1       anton     100: 
1.20      pazsan    101: : update ( -- ) \ block
1.29      crook     102:     \G Mark the state of the current block buffer as assigned-dirty.
1.5       pazsan    103:     last-block @ ?dup IF  buffer-dirty on  THEN ;
1.1       anton     104: 
1.20      pazsan    105: : save-buffer ( buffer -- ) \ gforth
                    106:     >r
1.5       pazsan    107:     r@ buffer-dirty @ r@ buffer-block @ 0<> and
1.1       anton     108:     if
1.5       pazsan    109:        r@ buffer-block @ block-position
                    110:        r@ block-buffer chars/block  r@ buffer-fid @  write-file throw
                    111:        r@ buffer-dirty off
                    112:     endif
                    113:     rdrop ;
                    114: 
1.20      pazsan    115: : empty-buffer ( buffer -- ) \ gforth
1.5       pazsan    116:     buffer-block off ;
                    117: 
1.20      pazsan    118: : save-buffers  ( -- ) \ block
1.24      crook     119:     \G Transfer the contents of each @code{update}d block buffer to
1.30      anton     120:     \G mass storage, then mark all block buffers as assigned-clean.
1.20      pazsan    121:     block-buffers @
1.24      crook     122:     buffers 0 ?DO dup save-buffer next-buffer LOOP drop ;
1.1       anton     123: 
1.24      crook     124: : empty-buffers ( -- ) \ block-ext
                    125:     \G Mark all block buffers as unassigned; if any had been marked as
                    126:     \G assigned-dirty (by @code{update}), the changes to those blocks
                    127:     \G will be lost.
1.20      pazsan    128:     block-buffers @
1.24      crook     129:     buffers 0 ?DO dup empty-buffer next-buffer LOOP drop ;
1.1       anton     130: 
1.20      pazsan    131: : flush ( -- ) \ block
1.24      crook     132:     \G Perform the functions of @code{save-buffers} then
                    133:     \G @code{empty-buffers}.
1.1       anton     134:     save-buffers
                    135:     empty-buffers ;
                    136: 
1.12      anton     137: ' flush IS flush-blocks
1.5       pazsan    138: 
1.26      pazsan    139: : get-buffer ( u -- a-addr ) \ gforth
                    140:     0 buffers um/mod drop buffer-struct %size * block-buffers @ + ;
1.5       pazsan    141: 
1.28      crook     142: : block ( u -- a-addr ) \ gforthman- block
1.24      crook     143:     \G If a block buffer is assigned for block @i{u}, return its
                    144:     \G start address, @i{a-addr}. Otherwise, assign a block buffer
                    145:     \G for block @i{u} (if the assigned block buffer has been
                    146:     \G @code{update}d, transfer the contents to mass storage), read
                    147:     \G the block into the block buffer and return its start address,
                    148:     \G @i{a-addr}.
1.26      pazsan    149:     dup offset @ u< -35 and throw
1.5       pazsan    150:     dup get-buffer >r
                    151:     dup r@ buffer-block @ <>
1.9       pazsan    152:     r@ buffer-fid @ block-fid @ <> or
1.1       anton     153:     if
1.5       pazsan    154:        r@ save-buffer
1.1       anton     155:        dup block-position
1.5       pazsan    156:        r@ block-buffer chars/block get-block-fid read-file throw
1.1       anton     157:        \ clear the rest of the buffer if the file is too short
1.5       pazsan    158:        r@ block-buffer over chars + chars/block rot chars - blank
                    159:        r@ buffer-block !
                    160:        get-block-fid r@ buffer-fid !
1.1       anton     161:     else
                    162:        drop
                    163:     then
1.5       pazsan    164:     r> dup last-block ! block-buffer ;
1.1       anton     165: 
1.20      pazsan    166: : buffer ( u -- a-addr ) \ block
1.24      crook     167:     \G If a block buffer is assigned for block @i{u}, return its
                    168:     \G start address, @i{a-addr}. Otherwise, assign a block buffer
                    169:     \G for block @i{u} (if the assigned block buffer has been
                    170:     \G @code{update}d, transfer the contents to mass storage) and
                    171:     \G return its start address, @i{a-addr}.  The subtle difference
                    172:     \G between @code{buffer} and @code{block} mean that you should
                    173:     \G only use @code{buffer} if you don't care about the previous
                    174:     \G contents of block @i{u}. In Gforth, this simply calls
                    175:     \G @code{block}.
1.1       anton     176:     \ reading in the block is unnecessary, but simpler
                    177:     block ;
                    178: 
1.28      crook     179: User scr ( -- a-addr ) \ block-ext s-c-r
1.27      crook     180:     \G @code{User} variable -- @i{a-addr} is the address of a cell containing
1.21      crook     181:     \G the block number of the block most recently processed by
1.24      crook     182:     \G @code{list}.
                    183: 0 scr !
1.1       anton     184: 
1.24      crook     185: \ nac31Mar1999 moved "scr @" to list to make the stack comment correct
1.20      pazsan    186: : updated?  ( n -- f ) \ gforth
1.29      crook     187:     \G Return true if @code{updated} has been used to mark block @i{n}
                    188:     \G as assigned-dirty.
1.24      crook     189:     buffer
1.5       pazsan    190:     [ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
                    191: 
1.24      crook     192: : list ( u -- ) \ block-ext
                    193:     \G Display block @i{u}. In Gforth, the block is displayed as 16
                    194:     \G numbered lines, each of 64 characters.
1.1       anton     195:     \ calling block again and again looks inefficient but is necessary
                    196:     \ in a multitasking environment
                    197:     dup scr !
1.5       pazsan    198:     ." Screen " u.
1.24      crook     199:     scr @ updated?  0= IF ." not "  THEN  ." modified     " cr
1.1       anton     200:     16 0
                    201:     ?do
1.4       anton     202:        i 2 .r space scr @ block i 64 * chars + 64 type cr
1.1       anton     203:     loop ;
                    204: 
1.23      crook     205: : (source)  ( -- c-addr u )
1.2       pazsan    206:   blk @ ?dup
                    207:   IF    block chars/block
                    208:   ELSE  tib #tib @
                    209:   THEN ;
                    210: 
1.23      crook     211: ' (source) IS source ( -- c-addr u ) \ core
1.24      crook     212: \G @i{c-addr} is the address of the input buffer and @i{u} is the
1.23      crook     213: \G number of characters in it.
1.2       pazsan    214: 
1.20      pazsan    215: : load ( i*x n -- j*x ) \ block
1.24      crook     216:     \G Save the current input source specification. Store @i{n} in
                    217:     \G @code{BLK}, set @code{>IN} to 0 and interpret. When the parse
                    218:     \G area is exhausted, restore the input source specification.
1.31    ! anton     219:     loadfilename# @ >r
        !           220:     2 loadfilename# ! \ "\a block/"
1.24      crook     221:     push-file
                    222:     dup loadline ! blk ! >in off ['] interpret catch
1.31    ! anton     223:     pop-file
        !           224:     r> loadfilename# !
        !           225:     throw ;
1.24      crook     226: 
                    227: : thru ( i*x n1 n2 -- j*x ) \ block-ext
                    228:     \G @code{load} the blocks @i{n1} through @i{n2} in sequence.
                    229:     1+ swap ?DO  I load  LOOP ;
                    230: 
                    231: : +load ( i*x n -- j*x ) \ gforth
                    232:     \G Used within a block to load the block specified as the
                    233:     \G current block + @i{n}.
1.20      pazsan    234:     blk @ + load ;
1.2       pazsan    235: 
1.24      crook     236: : +thru ( i*x n1 n2 -- j*x ) \ gforth
                    237:     \G Used within a block to load the range of blocks specified as the
                    238:     \G current block + @i{n1} thru the current block + @i{n2}.
                    239:     1+ swap ?DO  I +load  LOOP ;
                    240: 
1.28      crook     241: : --> ( -- ) \ gforthman- gforth chain
1.24      crook     242:     \G If this symbol is encountered whilst loading block @i{n},
                    243:     \G discard the remainder of the block and load block @i{n+1}. Used
1.25      anton     244:     \G for chaining multiple blocks together as a single loadable
                    245:     \G unit.  Not recommended, because it destroys the independence of
                    246:     \G loading.  Use @code{thru} (which is standard) or @code{+thru}
                    247:     \G instead.
1.20      pazsan    248:     refill drop ; immediate
1.5       pazsan    249: 
1.24      crook     250: : block-included ( a-addr u -- ) \ gforth
                    251:     \G Use within a block that is to be processed by @code{load}. Save
                    252:     \G the current blocks file specification, open the blocks file
                    253:     \G specified by @i{a-addr u} and @code{load} block 1 from that
                    254:     \G file (which may in turn chain or load other blocks). Finally,
                    255:     \G close the blocks file and restore the original blocks file.
1.11      anton     256:     block-fid @ >r block-fid off open-blocks
1.5       pazsan    257:     1 load block-fid @ close-file throw flush
                    258:     r> block-fid ! ;
                    259: 
1.13      anton     260: \ thrown out because it may provide unpleasant surprises - anton
                    261: \ : include ( "name" -- )
                    262: \     name 2dup dup 3 - /string s" .fb" compare
                    263: \     0= IF  block-included  ELSE  included  THEN ;
1.5       pazsan    264: 
1.4       anton     265: get-current environment-wordlist set-current
                    266: true constant block
                    267: true constant block-ext
                    268: set-current
1.5       pazsan    269: 
1.21      crook     270: : bye ( -- ) \ tools-ext
                    271:   \G Return control to the host operating system (if any).
                    272:   ['] flush catch drop bye ;

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