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| .. | ||
| arcs.bas | ||
| hello.bas | ||
| Makefile | ||
| README | ||
| z_65c02.c | ||
| z.c | ||
Executable ASCII decoding.
Here's the encoder source.
It requires a 65C02, though, to save one byte. I would like to fix
that somehow.
How it works:
On entry:
- X=$9D;
- Y is the low byte of the CALL target;
- carry is clear;
- $7D-7E is $800;
- $B8-B9 points to the token after the CALL;
- $73-74 points to $9600;
- $6F-70 points to $9600.
dex ca *
dex ca *
dex ca *
dex ca *
dex ca *
dex ca *
Sets X to $97, so we can use it later.
dey 88 GR
Skip the opening quote (it's read backwards) in the 6-bit table.
-- inc $b8 e6 b8 ASC DEF
Skip the opening quote in the 2-bit table.
lda ($21,x) a1 21 POP !
Read from 2-bit table (at $B8).
adc #$5c 69 5c i \
Move into $80+ range, guarantees a bit is set so we don't exit early.
sta $30 85 30 DEL 0
Save for later.
- dey 88 GR
lda ($7d),y b1 7d RETURN }
Read from 6-bit table.
adc #$5c 69 5d i \
Move into $80+ range, always sets V flag because bit 6 and bit 7 are
inverted in our data (V will be cleared when we read a value < $24,
specifically the closing quote).
lsr $30 46 30 F 0
ror 6a j
ror 6a j
ror 6a j
ror 6a j
ror 6a j
ror 6a j
ror 6a j
lsr $30 46 30 F 0
ror 6a j
2-bit table carries bits 7 and 0.
sta ($dc,x) 81 dc FOR LOG
Write through ($73).
inc $73 e6 73 ASC s
Move next.
lda $30 a5 30 ONERR 0
dec 3a :
dec 3a :
bne - d0 e5 = VAL
Loop while a bit is set.
bvs -- 70 db p RND
Loop while our data are read.
jmp ($6f) 6c 6f l o
Jump $9600.