collapseos/forth/link.fs
Virgil Dupras f3c92684a0 link: improve reliability by never relinking last word
It's not possible to reliably determine its end and with some memory
initialization scenarios, it makes RLDICT fail.
2020-04-18 16:51:48 -04:00

185 lines
6.1 KiB
Forth

( depends: cmp, parse
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, identify the
root word of the source part, probably "H@", and run
" ' thatword RLDICT ". Then, take the resulting relinked
binary, concatenate it to the boot binary, and write to
boot media.
LIMITATIONS
This unit can't automatically detect all offsets needing
relinking. This is a list of situations that aren't handled:
Cells: It's not possible to know for sure whether a cellWord
contains an address or a number. They are therefore not
automatically relinked. You have to manually relink each of
them with RLCELL. In the case of a DOES> word, PFA+2, which
is always an offset, is automatically relinked, but not
PFA+0.
)
( Skip atom, considering special atom types. )
( a -- a+n )
: ASKIP
DUP @ ( a n )
( ?br or br or NUMBER )
DUP <>{ 0x67 &= 0x53 |= 0x20 |= 0x24 |= <>}
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
( skip null char )
1+
;
( 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 )
DUP 0x24 = IF
( 0x24 is an addrWord, which should be offsetted in
the same way that a regular word would. To achieve
this, we skip ASKIP and instead of skipping 4 bytes
like a numberWord, we skip only 2, which means that
our number will be treated like a regular wordref.
)
DROP
2+ ( o ol a+2 )
ROT ROT 2DROP ( a )
EXIT
THEN
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 C@ ( ol o a2 a1 n )
( 0e == compiledWord, 2b == doesWord )
DUP <>{ 0x0e &= 0x2b |= <>} NOT IF
( unwind all args )
2DROP 2DROP
EXIT
THEN
( we have a compiled word or doesWord, proceed )
( doesWord is processed exactly like a compiledWord, but
starts 2 bytes further. )
( ol o a2 a1 n )
0x2b = IF 2+ THEN
( ol o a2 a1 )
1+ ( ol o a2 a1+1 )
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 < IF ABORT THEN ( Something is very wrong )
2DUP = ( ol o a2 a+n f )
IF
( unwind )
2DROP 2DROP
EXIT
THEN
AGAIN
;
( TODO implement RLCELL )
( 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.
The output of this word is 3 numbers: top copied address,
top copied CURRENT, and then the beginning of the copied dict
at the end to indicate that we're finished processing.
Note that the last word is always skipped because it's not
possible to reliably detect its end. If you need that last
word, define a dummy word before calling RLDICT.
)
( target -- )
: RLDICT
( 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 RLDICT 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@ @ WORD( ( 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 CURRENT @ WORD( + ( u we )
DUP .X CRLF
SWAP CURRENT @ PREV + ( we wr )
DUP .X CRLF
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 )
WORD( ( wr we )
SWAP ( we wr )
( Are we finished? We're finished if wr-4 <= H@ )
DUP 4 - H@ <=
UNTIL
H@ 4 + .X CRLF
;
( Relink a regular Forth full interpreter. )
: RLCORE
LIT< H@ (find) DROP RLDICT
;