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Diffstat (limited to 'comptitle.s.in')
| -rw-r--r-- | comptitle.s.in | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/comptitle.s.in b/comptitle.s.in new file mode 100644 index 0000000..7862b3d --- /dev/null +++ b/comptitle.s.in @@ -0,0 +1,116 @@ + +; cl65 -o comptitle.xex -t none comptitle.s + +; comptitle.s.in is used by titlecomp.pl, to generate comptitle.s. +; __VARIABLE__ stuff is filled in by titlecomp.pl, q.v. +; DON'T bother to edit comptitle.s (edit the .in file instead)! + + .include "atari.inc" + + ; size of uncompressed image, in bytes (but, needs to be + ; a multiple of $100). +;imgsize = __SIZE__ +imgsize = $1700 + + ; these both need to be page-aligned. destination also needs + ; to be aligned on a 4K boundary. +start = $2000 +destination = $9000 + +srcptr = FR0 +dstptr = FR0+2 +pagecount = FR0+4 +tmp = FR0+5 + + .word $ffff + .word start + .word end-1 + + .org start + +compdata: + .incbin "comptitle.dat" + +; table runs __FIRSTCODE__ to __LASTCODE__ +table: + __TABLE__ + + ; decompression code starts here +init: + lda #>imgsize + sta pagecount + lda #>compdata + sta srcptr+1 + lda #>destination + sta dstptr+1 + lda #0 + sta srcptr + sta dstptr + tay + +copyloop: + lda (srcptr),y + bpl storebyte ; 0-127 always represent themselves + cmp #__LASTCODE__+1 + bcs storebyte ; anything above the last code represents itself + sta tmp + sec + sbc #__FIRSTCODE__ + bcc notcode ; anything below the 1st code represents itself + tax + lda table,x + beq notcode + + ; got a zero-run code. A = number of bytes of zeroes to store. + jmp storezerorun + +notcode: + lda tmp + +storebyte: + sty tmp + ldy #0 + sta (dstptr),y + jsr incdest + beq done +nohi: + ldy tmp + +storedone: + iny + bne copyloop + inc srcptr+1 + bne copyloop ; always branch (since srcptr never wraps around to 0) + +done: + rts + +storezerorun: + sty tmp + tay + dey + lda #0 +szloop: + sta (dstptr),y + jsr incdest + beq done +nohi2: + dey + bpl szloop + + ldy tmp + jmp storedone + +incdest: + inc dstptr + bne iddone + inc dstptr+1 + dec pagecount +iddone: + rts + +end: + .word INITAD + .word INITAD+1 + .word init + |