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