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Length: 2515 (0x9d3)
Types: TextFile
Notes: UNIX file
Names: »scroll.s«
└─⟦f27320a65⟧ Bits:30001972 Commodore 900 hard disk image with partial source code
└─⟦926b8033d⟧ UNIX V7 Filesystem
└─ ⟦this⟧ »u/demo/slide/scroll.s«
.globl scroll_, scantab_, aldir_, linerase_, nulls_ SEG0 = 0x3a000000 / first screen segment SEG1 = 0x3b000000 / second screen segment YMAX = 800 / scan lines per screen YSPLIT = 512 / scan line that crossed into SEG1 YSCROLL = 25 / scrolling increment MAXLINE = 32 / YMAX / YSCROLL WPERSL = 64 / words per scan line BPERSL = WPERSL * 2 / bytes per scan line SS = 0x3F3F / system stack OS = 0x3e3e / rr2 pointer to scan line data / rr4 reference pointer to screen / r6 a word offset into the screen / r7 word count / rr8 source pointer / rr10 destination pointer scroll_: pushl (rr14), rr10 pushl (rr14), rr8 push (rr14), r7 push (rr14), r6 pushl (rr14), rr4 pushl (rr14), rr2 ldl rr2, $scantab_+YSCROLL*2 ldl rr4, $SEG0 + YSCROLL*BPERSL ld r8, r4 ld r10, r4 jr 1f 0: add r5, $BPERSL jr c, 2f 1: ld r6, (rr2) ld OS|[-YSCROLL*2](r3), r6 inc r3, $2 xor r7, r7 orb rl7, rl6 jr z, 0b ldb rl6, rh6 xorb rh6, rh6 add r6, r6 ld r9, r5 add r9, r6 ld r11, r9 sub r11, $YSCROLL*BPERSL ldir (rr10), (rr8), r7 jr 0b 2: ldl rr4, $SEG0+0x10000-YSCROLL*BPERSL ldl rr8, $SEG1 jr 1f 0: add r5, $BPERSL jr c, 2f 1: ld r6, (rr2) ld OS|[-YSCROLL*2](r3), r6 inc r3, $2 xor r7, r7 orb rl7, rl6 jr z, 0b ldb rl6, rh6 xorb rh6, rh6 add r6, r6 ld r11, r5 add r11, r6 ld r9, r11 add r9, $YSCROLL*BPERSL ldir (rr10), (rr8), r7 jr 0b 2: ldl rr4, $SEG1+YSCROLL*BPERSL ld r10, r4 jr 1f 0: add r5, $BPERSL cp r3, $scantab_+YMAX*2 jr z, 2f 1: ld r6, (rr2) ld OS|[-YSCROLL*2](r3), r6 inc r3, $2 xor r7, r7 orb rl7, rl6 jr z, 0b ldb rl6, rh6 xorb rh6, rh6 add r6, r6 ld r9, r5 add r9, r6 ld r11, r9 sub r11, $YSCROLL*BPERSL ldir (rr10), (rr8), r7 jr 0b 2: ldl rr8, $nulls_ ld r11, $[[MAXLINE-1]*YSCROLL-YSPLIT]*BPERSL ld r7, $YSCROLL*WPERSL ldir (rr10), (rr8), r7 popl rr2, (rr14) popl rr4, (rr14) pop r6, (rr14) pop r7, (rr14) popl rr8, (rr14) popl rr10, (rr14) ret aldir_: dec r15, $12 ldm (rr14), r8, $6 ld r13, r15 ldl rr10, SS|16(r13) ldl rr8, SS|20(r13) ld r12, SS|24(r13) ldir (rr10), (rr8), r12 ldm r8, (rr14), $6 inc r15, $12 ret //////// / / erase text line / linerase( line) / YSCROLL scan lines are filled with nulls, starting at text line `line'. / linerase_: ld r1, SS|4(r15) mult rr0, $YSCROLL ldl rr4, $SEG0 cp r1, $YSPLIT jr c, 1f ldl rr4, $SEG1 sub r1, $YSPLIT 1: mult rr0, $BPERSL ld r5, r1 ldl rr2, $nulls_ ld r0, $YSCROLL*WPERSL ldir (rr4), (rr2), r0 ret .bssd nulls_: .blkw YSCROLL * WPERSL