\ block words


variable scr
variable recent-buffer
variable buffer-map
variable buffers-base
variable max-buffers
variable blockfile
variable max-blocks
variable bfname
create bfname0 bl string blockfile

: buffer-addr  ( n -- a ) 1024 * buffers-base @ + ;
: buffer-block  ( n -- a ) 2 cells * buffer-map @ + ;
: buffer-dirty  ( n -- a ) buffer-block cell+ ;

: open-blockfile  ( -- )
  blockfile @ 0= if bfname @ count r/w open-file ?fcheck 
  blockfile ! then ;

: update  ( -- ) recent-buffer @ buffer-dirty on ;

: save-buffer  ( n -- ) dup buffer-block @ 1024 *
  blockfile @ reposition-file ?fcheck dup buffer-addr 1024
  blockfile @ write-file ?fcheck buffer-dirty off ;

: flush  ( -- ) blockfile @ if max-buffers @ 0 do i 
  buffer-dirty @ if i save-buffer then loop then ;

: empty-buffers  ( -- ) buffer-map @ max-buffers @ 2 cells * 
  erase ;

: next-buffer  ( n1 -- n2 ) 1+ max-buffers @ mod ;

: buffer  ( n -- a ) max-buffers @ 0 do recent-buffer @ i +
  next-buffer dup buffer-dirty @ 0= if dup recent-buffer ! dup 
  >r buffer-block ! r> buffer-addr unloop exit then drop loop 
  recent-buffer @ next-buffer dup save-buffer dup recent-buffer 
  ! dup >r buffer-block ! r> buffer-addr ;

: block  ( n -- a ) open-blockfile
  max-buffers @ 0 do dup i buffer-block @ = if drop
  i buffer-addr i recent-buffer ! unloop exit then loop dup 
  1024 * blockfile @ reposition-file ?fcheck buffer dup 1024 
  blockfile @ read-file ?fcheck drop ;

: load  ( n -- ) >r save-input r@ blk ! r> block >r
  >in off 1024 >limit ! r> sourcebuf ! interpret restore-input 
  0= if space s" unable to restore input" type cr abort then
  blk @ ?dup if block sourcebuf ! then ;

: thru  ( n1 n2 -- ) 1+ swap do i load loop ;
: .row  ( n -- ) 2 .r [char] │ emit ;

: .blkhdr  ( n -- ) s"   ╭BLOCK: " type 4 u.r 
  s" ─────────────────────────────────────────────────────╮" type cr ;

: list  ( n -- ) base @ >r decimal dup scr ! dup .blkhdr 
  block 16 0 do i .row dup 64 type [char] │ emit cr 64 
  + loop drop r> base ! 
  s"   ╰────────────────────────────────────────────────────────────────╯" 
  type cr ;

: .buffers  ( -- ) base @ cr                                    
  ."   Buffer  Block  Dirty  Address" cr                        
  ."   ─────────────────────────────" cr                        
  max-buffers @ 0 do decimal                                    
   6 spaces i 2 .r 3 spaces i buffer-block @ 4 .r               
  4 spaces i buffer-dirty @ if [char] X else [char] - then      
  emit 3 spaces hex i buffer-addr 8 .r cr                       
  loop base ! ;                                                 
                                                                

\ initialization

16 max-buffers !
heaptop @ max-buffers @ 1024 * - buffers-base !
bfname0 bfname ! 1024 max-blocks !
buffers-base @ max-buffers @ 2 cells * - buffer-map !