--- gforth/blocks.fs	1998/12/08 22:02:36	1.19
+++ gforth/blocks.fs	2011/05/20 13:54:37	1.58
@@ -1,12 +1,12 @@
 \ A less simple implementation of the blocks wordset. 
 
-\ Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
+\ Copyright (C) 1995,1996,1997,1998,2000,2003,2006,2007,2008 Free Software Foundation, Inc.
 
 \ This file is part of Gforth.
 
 \ Gforth is free software; you can redistribute it and/or
 \ modify it under the terms of the GNU General Public License
-\ as published by the Free Software Foundation; either version 2
+\ as published by the Free Software Foundation, either version 3
 \ of the License, or (at your option) any later version.
 
 \ This program is distributed in the hope that it will be useful,
@@ -15,8 +15,7 @@
 \ GNU General Public License for more details.
 
 \ You should have received a copy of the GNU General Public License
-\ along with this program; if not, write to the Free Software
-\ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+\ along with this program. If not, see http://www.gnu.org/licenses/.
 
 
 \ A more efficient implementation would use mmap on OSs that
@@ -44,80 +43,121 @@ Variable last-block
 
 $20 Value buffers
 
+\ limit block files to 2GB; gforth <0.6.0 erases larger block files on
+\ 32-bit systems
+$200000 Value block-limit
+
 User block-fid
+User block-offset ( -- addr ) \ gforth
+\G User variable containing the number of the first block (default
+\G since 0.5.0: 0).  Block files created with Gforth versions before
+\G 0.5.0 have the offset 1.  If you use these files you can: @code{1
+\G offset !}; or add 1 to every block number used; or prepend 1024
+\G characters to the file.
+0 block-offset !  \ store 1 here fore 0.4.0 compatibility
+
+' block-offset alias offset \ !! eliminate this?
 
 : block-cold ( -- )
     block-fid off  last-block off
     buffer-struct buffers * %alloc dup block-buffers ! ( addr )
     buffer-struct %size buffers * erase ;
 
-' block-cold INIT8 chained
+:noname ( -- )
+    defers 'cold
+    block-cold
+; is 'cold
 
 block-cold
 
-Defer flush-blocks
+Defer flush-blocks ( -- ) \ gforth
 
-: open-blocks ( addr u -- ) \ gforth
-    \g use the file, whose name is given by @var{addr u}, as blocks file 
-    2dup open-fpath-file 0<>
-    if
-	r/w bin create-file throw
-    else
+: open-blocks ( c-addr u -- ) \ gforth
+\g Use the file, whose name is given by @i{c-addr u}, as the blocks file.
+    try ( c-addr u )
+	2dup open-fpath-file throw
 	rot close-file throw  2dup file-status throw bin open-file throw
 	>r 2drop r>
+    endtry-iferror ( c-addr u ior )
+	>r 2dup file-status nip 0= r> and throw \ does it really not exist?
+	r/w bin create-file throw
     then
-    block-fid @ IF  flush-blocks block-fid @ close-file throw  THEN
+    block-fid @ IF
+	flush-blocks block-fid @ close-file throw
+    THEN
     block-fid ! ;
 
 : use ( "file" -- ) \ gforth
-    \g use @var{file} as blocks file
-    name open-blocks ;
+    \g Use @i{file} as the blocks file.
+    name name-too-short? open-blocks ;
 
 \ the file is opened as binary file, since it either will contain text
 \ without newlines or binary data
-: get-block-fid ( -- fid )
+: get-block-fid ( -- wfileid ) \ gforth
+    \G Return the file-id of the current blocks file. If no blocks
+    \G file has been opened, use @file{blocks.fb} as the default
+    \G blocks file.
     block-fid @ 0=
     if
 	s" blocks.fb" open-blocks
     then
     block-fid @ ;
 
-: block-position ( u -- )
-    \ positions the block file to the start of block u
-    1- chars/block chars um* get-block-fid reposition-file throw ;
+: block-position ( u -- ) \ block
+\G Position the block file to the start of block @i{u}.
+    dup block-limit u>= -35 and throw
+    offset @ - chars/block chars um* get-block-fid reposition-file throw ;
 
-: update ( -- )
+: update ( -- ) \ block
+    \G Mark the state of the current block buffer as assigned-dirty.
     last-block @ ?dup IF  buffer-dirty on  THEN ;
 
-: save-buffer ( buffer -- ) >r
-    r@ buffer-dirty @ r@ buffer-block @ 0<> and
+: save-buffer ( buffer -- ) \ gforth
+    >r
+    r@ buffer-dirty @
     if
 	r@ buffer-block @ block-position
 	r@ block-buffer chars/block  r@ buffer-fid @  write-file throw
-	r@ buffer-dirty off
+	r@ buffer-fid @ flush-file throw
+	r@ buffer-dirty off 
     endif
     rdrop ;
 
-: empty-buffer ( buffer -- )
-    buffer-block off ;
-
-: save-buffers  ( -- )    block-buffers @
-    buffers 0 ?DO  dup save-buffer  next-buffer  LOOP  drop ;
-
-: empty-buffers ( -- )    block-buffers @
-    buffers 0 ?DO  dup empty-buffer  next-buffer  LOOP  drop ;
+: empty-buffer ( buffer -- ) \ gforth
+    dup buffer-block on buffer-dirty off ;
 
-: flush ( -- )
+: save-buffers  ( -- ) \ block
+    \G Transfer the contents of each @code{update}d block buffer to
+    \G mass storage, then mark all block buffers as assigned-clean.
+    block-buffers @
+    buffers 0 ?DO dup save-buffer next-buffer LOOP drop ;
+
+: empty-buffers ( -- ) \ block-ext
+    \G Mark all block buffers as unassigned; if any had been marked as
+    \G assigned-dirty (by @code{update}), the changes to those blocks
+    \G will be lost.
+    block-buffers @
+    buffers 0 ?DO dup empty-buffer next-buffer LOOP drop ;
+
+: flush ( -- ) \ block
+    \G Perform the functions of @code{save-buffers} then
+    \G @code{empty-buffers}.
     save-buffers
     empty-buffers ;
 
 ' flush IS flush-blocks
 
-: get-buffer ( n -- a-addr )
-    buffers mod buffer-struct %size * block-buffers @ + ;
+: get-buffer ( u -- a-addr ) \ gforth
+    0 buffers um/mod drop buffer-struct %size * block-buffers @ + ;
 
-: block ( u -- a-addr )
-    dup 0= -35 and throw
+: block ( u -- a-addr ) \ block
+    \G If a block buffer is assigned for block @i{u}, return its
+    \G start address, @i{a-addr}. Otherwise, assign a block buffer
+    \G for block @i{u} (if the assigned block buffer has been
+    \G @code{update}d, transfer the contents to mass storage), read
+    \G the block into the block buffer and return its start address,
+    \G @i{a-addr}.
+    dup offset @ u< -35 and throw
     dup get-buffer >r
     dup r@ buffer-block @ <>
     r@ buffer-fid @ block-fid @ <> or
@@ -134,50 +174,111 @@ Defer flush-blocks
     then
     r> dup last-block ! block-buffer ;
 
-: buffer ( u -- a-addr )
+: buffer ( u -- a-addr ) \ block
+    \G If a block buffer is assigned for block @i{u}, return its
+    \G start address, @i{a-addr}. Otherwise, assign a block buffer
+    \G for block @i{u} (if the assigned block buffer has been
+    \G @code{update}d, transfer the contents to mass storage) and
+    \G return its start address, @i{a-addr}.  The subtle difference
+    \G between @code{buffer} and @code{block} mean that you should
+    \G only use @code{buffer} if you don't care about the previous
+    \G contents of block @i{u}. In Gforth, this simply calls
+    \G @code{block}.
     \ reading in the block is unnecessary, but simpler
     block ;
 
-User scr 0 scr !
-
-: updated?  ( n -- f )   scr @ buffer
+User scr ( -- a-addr ) \ block-ext s-c-r
+    \G @code{User} variable -- @i{a-addr} is the address of a cell containing
+    \G the block number of the block most recently processed by
+    \G @code{list}.
+0 scr !
+
+\ nac31Mar1999 moved "scr @" to list to make the stack comment correct
+: updated?  ( n -- f ) \ gforth
+    \G Return true if @code{updated} has been used to mark block @i{n}
+    \G as assigned-dirty.
+    buffer
     [ 0 buffer-dirty 0 block-buffer - ] Literal + @ ;
 
-: list ( u -- )
+: list ( u -- ) \ block-ext
+    \G Display block @i{u}. In Gforth, the block is displayed as 16
+    \G numbered lines, each of 64 characters.
     \ calling block again and again looks inefficient but is necessary
     \ in a multitasking environment
     dup scr !
     ." Screen " u.
-    updated?  0= IF ." not "  THEN  ." modified     " cr
+    scr @ updated?  0= IF ." not "  THEN  ." modified     " cr
     16 0
     ?do
 	i 2 .r space scr @ block i 64 * chars + 64 type cr
     loop ;
 
-: (source)  ( -- addr len )
+[IFDEF] current-input
+:noname  2 <> -12 and throw >in ! blk ! ;
+                              \ restore-input
+:noname  blk @ >in @ 2 ;      \ save-input
+:noname  2 ;                  \ source-id "*a block*"
+:noname  1 blk +! 1 loadline +! >in off true ;      \ refill
+:noname  blk @ block chars/block ;  \ source
+
+Create block-input   A, A, A, A, A,
+
+: load  ( i*x u -- j*x ) \ block
+    \g Text-interpret block @i{u}.  Block 0 cannot be @code{load}ed.
+    dup 0= -35 and throw
+    block-input 0 new-tib dup loadline ! blk !  s" * a block*" loadfilename 2!
+    ['] interpret catch pop-file throw ;
+[ELSE]
+: (source)  ( -- c-addr u )
   blk @ ?dup
   IF    block chars/block
   ELSE  tib #tib @
   THEN ;
 
-' (source) IS source
-
-: load ( i*x n -- j*x )
-  push-file
-  dup loadline ! blk ! >in off ['] interpret catch
-  pop-file throw ;
-
-: thru ( i*x n1 n2 -- j*x )
-  1+ swap ?DO  I load  LOOP ;
+' (source) IS source ( -- c-addr u ) \ core
+\G @i{c-addr} is the address of the input buffer and @i{u} is the
+\G number of characters in it.
 
-: +load ( i*x n -- j*x )  blk @ + load ;
-
-: +thru ( i*x n1 n2 -- j*x )
-  1+ swap ?DO  I +load  LOOP ;
-
-: --> ( -- )  refill drop ; immediate
-
-: block-included ( addr u -- )
+: load ( i*x u -- j*x ) \ block
+    \g Text-interpret block @i{u}.  Block 0 cannot be @code{load}ed.
+    dup 0= -35 and throw
+    s" * a block*" loadfilename>r
+    push-file
+    dup loadline ! blk ! >in off ['] interpret catch
+    pop-file
+    r>loadfilename
+    throw ;
+[THEN]
+
+: thru ( i*x n1 n2 -- j*x ) \ block-ext
+    \G @code{load} the blocks @i{n1} through @i{n2} in sequence.
+    1+ swap ?DO  I load  LOOP ;
+
+: +load ( i*x n -- j*x ) \ gforth
+    \G Used within a block to load the block specified as the
+    \G current block + @i{n}.
+    blk @ + load ;
+
+: +thru ( i*x n1 n2 -- j*x ) \ gforth
+    \G Used within a block to load the range of blocks specified as the
+    \G current block + @i{n1} thru the current block + @i{n2}.
+    1+ swap ?DO  I +load  LOOP ;
+
+: --> ( -- ) \ gforthman- gforth chain
+    \G If this symbol is encountered whilst loading block @i{n},
+    \G discard the remainder of the block and load block @i{n+1}. Used
+    \G for chaining multiple blocks together as a single loadable
+    \G unit.  Not recommended, because it destroys the independence of
+    \G loading.  Use @code{thru} (which is standard) or @code{+thru}
+    \G instead.
+    refill drop ; immediate
+
+: block-included ( a-addr u -- ) \ gforth
+    \G Use within a block that is to be processed by @code{load}. Save
+    \G the current blocks file specification, open the blocks file
+    \G specified by @i{a-addr u} and @code{load} block 1 from that
+    \G file (which may in turn chain or load other blocks). Finally,
+    \G close the blocks file and restore the original blocks file.
     block-fid @ >r block-fid off open-blocks
     1 load block-fid @ close-file throw flush
     r> block-fid ! ;
@@ -188,8 +289,10 @@ User scr 0 scr !
 \     0= IF  block-included  ELSE  included  THEN ;
 
 get-current environment-wordlist set-current
-true constant block
+true constant block \ environment- environment
 true constant block-ext
 set-current
 
-: bye  ['] flush catch drop bye ;
+: bye ( -- ) \ tools-ext
+  \G Return control to the host operating system (if any).
+  ['] flush catch drop bye ;