collapseos/forth/link.fs

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( depends: cmp
Relink a dictionary by applying offsets to all word
references in words of the "compiled" type.
A typical usage of this unit would be to, right after a
bootstrap-from-icore-from-source operation, to copy the
dictionary from '< H@ to CURRENT, and then call RLDICT on
that new range, with "ol" set to ' H@.
)
( Skip atom, considering special atom types. )
( a -- a+n )
: ASKIP
DUP @ ( a n )
( ?br or br or NUMBER )
DUP <>{ 0x70 &= 0x58 |= 0x20 |= <>}
IF DROP 4 + EXIT THEN
( regular word )
0x22 = NOT IF 2 + EXIT THEN
( it's a lit, skip to null char )
( a )
1 + ( we skip by 2, but the loop below is pre-inc... )
BEGIN 1 + DUP C@ NOT UNTIL
( a+1 )
;
( Get word header length from wordref. That is, name length
+ 3. a is a wordref )
( a -- n )
: WHLEN
1 - C@ ( name len field )
0x7f AND ( remove IMMEDIATE flag )
3 + ( fixed header len )
;
( Get word addr, starting at name's address )
: '< ' DUP WHLEN - ;
( Relink atom at a, applying offset o with limit ol.
Returns a, appropriately skipped.
)
( a o ol -- a+n )
: RLATOM
ROT ( o ol a )
DUP @ ( o ol a n )
ROT ( o a n ol )
< IF ( under limit, do nothing )
SWAP DROP ( a )
ELSE
( o a )
SWAP OVER @ ( a o n )
-^ ( a n-o )
OVER ! ( a )
THEN
ASKIP
;
( Relink a word with specified offset. If it's not of the type
"compiled word", ignore. If it is, advance in word until a2
is met, and for each word that is above ol, reduce that
reference by o.
Arguments: a1: wordref a2: word end addr o: offset to apply
ol: offset limit. don't apply on refs under it.
)
( ol o a1 a2 -- )
: RLWORD
SWAP DUP @ ( ol o a2 a1 n )
( 0e == compiledWord )
0x0e = NOT IF
( unwind all args )
2DROP 2DROP
EXIT
THEN
( we have a compiled word, proceed )
( ol o a2 a1 )
2 + ( ol o a2 a1+2 )
BEGIN ( ol o a2 a1 )
2OVER ( ol o a2 a1 ol o )
SWAP ( ol o a2 a1 o ol )
RLATOM ( ol o a2 a+n )
2DUP = ( ol o a2 a+n f )
IF
( unwind )
2DROP 2DROP
EXIT
THEN
AGAIN
;
( Get word's prev offset )
( a -- a )
: PREV
3 - DUP @ ( a o )
- ( a-o )
;
( Copy dict from target wordref, including header, up to HERE.
We're going to compact the space between that word and its
prev word. To do this, we're copying this whole memory area
in HERE and then iterate through that copied area and call
RLWORD on each word. That results in a dict that can be
concatenated to target's prev entry in a more compact way.
This copy of data doesn't allocate anything, so H@ doesn't
move. Moreover, we reserve 4 bytes at H@ to write our target
and offset because otherwise, things get too complicated
with the PSP.
This word prints the top copied address, so when comes the
time to concat boot binary with this relinked dict, you
can use H@+4 to printed addr.
)
( target -- )
: COMPACT
( First of all, let's get our offset. It's easy, it's
target's prev field, which is already an offset, minus
its name length. We expect, in COMPACT, that a target's
prev word is a "hook word", that is, an empty word. )
( H@ == target )
DUP H@ !
DUP 1 - C@ 0x7f AND ( t namelen )
SWAP 3 - @ ( namelen po )
-^ ( o )
( H@+2 == offset )
H@ 2 + ! ( )
( We have our offset, now let's copy our memory chunk )
H@ @ DUP WHLEN - ( src )
DUP H@ -^ ( src u )
DUP ROT SWAP ( u src u )
H@ 4 + ( u src u dst )
SWAP ( u src dst u )
MOVE ( u )
( Now, let's iterate that dict down )
( wr == wordref we == word end )
( To get our wr and we, we use H@ and CURRENT, which we
offset by u+4. +4 before, remember, we're using 4 bytes
as variable space. )
4 + ( u+4 )
DUP H@ + ( u we )
DUP .X LF
SWAP CURRENT @ + ( we wr )
BEGIN ( we wr )
DUP ROT ( wr wr we )
( call RLWORD. we need a sig: ol o wr we )
H@ @ ( wr wr we ol )
H@ 2 + @ ( wr wr we ol o )
2SWAP ( wr ol o wr we )
RLWORD ( wr )
( wr becomes wr's prev and we is wr-header )
DUP ( wr wr )
PREV ( oldwr newwr )
SWAP ( wr oldwr )
DUP WHLEN - ( wr we )
SWAP ( we wr )
( Are we finished? We're finished if wr-4 <= H@ )
DUP 4 - H@ <=
UNTIL
;