tridoraemu,docs: emulate vgafb shifter/maskgen and new iomem layout

tridoraemu/framebuffer.go

@@ -10,11 +10,16 @@ import (
 const VmemWords = 32768
 const PaletteSlots = 16
 const FB_RA = 0
-const FB_WA = 1
-const FB_IO = 2
-const FB_PS = 3
-const FB_PD = 4
-const FB_CTL= 5
+const FB_WA = 4
+const FB_IO = 8
+const FB_PS = 12
+const FB_PD = 16
+const FB_CTL= 20
+const FB_SHIFTER = 24
+const FB_SHIFTCOUNT = 28
+const FB_SHIFTERM = 32
+const FB_SHIFTERSP = 36
+const FB_MASKGEN = 40
 
 const PixelMask = 0b11110000000000000000000000000000
 const PixelPerWord = 8
@@ -33,6 +38,9 @@ type Framebuffer struct {
 	vmem [VmemWords]word
 	readCount int
         paletteChanged bool
+	shiftAssistData word
+	shiftAssistCount int
+	maskGenData word
 }
 
 func (f *Framebuffer) initialize() {
@@ -53,6 +61,11 @@ func (f *Framebuffer) read(byteaddr word) (word, error) {
 	case FB_PS: result = f.paletteSlot
 	case FB_PD: result = f.readPalette()
 	case FB_CTL: result = f.readCtl()
+	case FB_SHIFTER: result = f.readShiftAssist()
+	case FB_SHIFTCOUNT: result = 0xFFFFFFF
+	case FB_SHIFTERM: result = f.readShifterM()
+	case FB_SHIFTERSP: result = f.readShifterSp()
+	case FB_MASKGEN: result = f.readMaskGen()
 	default:
 	}
 	return result, nil
@@ -67,6 +80,11 @@ func (f *Framebuffer) write(value word, byteaddr word) (error) {
 	case FB_PS: f.paletteSlot = value
 	case FB_PD: f.writePalette(value)
 	case FB_CTL: f.writeCtl(value)
+	case FB_SHIFTER: f.writeShiftAssist(value)
+	case FB_SHIFTCOUNT: f.writeShiftCount(value)
+	case FB_SHIFTERM:
+	case FB_SHIFTERSP:
+	case FB_MASKGEN: f.writeMaskGen(value)
 	default:
 	}
 
@@ -152,3 +170,47 @@ func (f *Framebuffer) readCtl() word {
 
 func (f *Framebuffer) writeCtl(value word) {
 }
+
+func (f *Framebuffer) writeShiftAssist(value word) {
+	f.shiftAssistData = value
+	f.shiftAssistCount = 0
+}
+
+func (f *Framebuffer) readShiftAssist() word {
+	return f.shiftAssistData >> (f.shiftAssistCount * 4)
+}
+
+func (f *Framebuffer) writeShiftCount(value word) {
+	f.shiftAssistCount = int(value & 0x7)
+}
+
+func (f *Framebuffer) readShifterM() word {
+	return convertToMask(f.readShiftAssist())
+}
+
+func pixelToMask(pixels word, mask word) word {
+	if (pixels & mask) != 0 { return  mask } else { return 0 }
+}
+
+func convertToMask(pixels word) word {
+	return  pixelToMask(pixels, 0xF0000000) |
+		pixelToMask(pixels, 0x0F000000) |
+		pixelToMask(pixels, 0x00F00000) |
+		pixelToMask(pixels, 0x000F0000) |
+		pixelToMask(pixels, 0x0000F000) |
+		pixelToMask(pixels, 0x00000F00) |
+		pixelToMask(pixels, 0x000000F0) |
+		pixelToMask(pixels, 0x0000000F)
+}
+
+func (f *Framebuffer) readShifterSp() word {
+	return word(f.shiftAssistData << ((8-f.shiftAssistCount)*4))
+}
+
+func (f *Framebuffer) writeMaskGen(value word) {
+	f.maskGenData = value
+}
+
+func (f *Framebuffer) readMaskGen() word {
+	return convertToMask(f.maskGenData)
+}