Mercurial > repos > blastem
changeset 1887:bb3edb4ec605
Small optimization to read_map_scroll
author | Michael Pavone <pavone@retrodev.com> |
---|---|
date | Sat, 21 Sep 2019 20:20:03 -0700 |
parents | 183b86ba0212 |
children | bd60e74fd173 |
files | vdp.c |
diffstat | 1 files changed, 6 insertions(+), 23 deletions(-) [+] |
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--- a/vdp.c Sat Sep 21 11:17:40 2019 -0700 +++ b/vdp.c Sat Sep 21 20:20:03 2019 -0700 @@ -1148,32 +1148,15 @@ context->v_offset = vscroll & v_offset_mask; //printf("%s | line %d, vsram: %d, vscroll: %d, v_offset: %d\n",(vsram_off ? "B" : "A"), line, context->vsram[context->regs[REG_MODE_3] & 0x4 ? column : 0], vscroll, context->v_offset); vscroll >>= vscroll_shift; - uint16_t hscroll_mask; - uint16_t v_mul; - switch(context->regs[REG_SCROLL] & 0x3) - { - case 0: - hscroll_mask = 0x1F; - v_mul = 64; - break; - case 0x1: - hscroll_mask = 0x3F; - v_mul = 128; - break; - case 0x2: - //TODO: Verify this behavior - hscroll_mask = 0x1F; - v_mul = 0; - break; - case 0x3: - hscroll_mask = 0x7F; - v_mul = 256; - break; - } + //TODO: Verify the behavior for a setting of 2 + static const uint16_t hscroll_masks[] = {0x1F, 0x3F, 0x1F, 0x7F}; + static const uint16_t v_shifts[] = {6, 7, 0, 8}; + uint16_t hscroll_mask = hscroll_masks[context->regs[REG_SCROLL] & 0x3]; + uint16_t v_shift = v_shifts[context->regs[REG_SCROLL] & 0x3]; uint16_t hscroll, offset; for (int i = 0; i < 2; i++) { hscroll = (column - 2 + i - ((hscroll_val/8) & 0xFFFE)) & hscroll_mask; - offset = address + ((vscroll * v_mul + hscroll*2) & 0x1FFF); + offset = address + (((vscroll << v_shift) + hscroll*2) & 0x1FFF); //printf("%s | line: %d, col: %d, x: %d, hs_mask %X, scr reg: %X, tbl addr: %X\n", (vsram_off ? "B" : "A"), line, (column-2+i), hscroll, hscroll_mask, context->regs[REG_SCROLL], offset); uint16_t col_val = (context->vdpmem[offset] << 8) | context->vdpmem[offset+1]; if (i) {