From 54e4676a0be40e4fdc56bd4427695ae3935113af Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Sun, 8 Nov 1992 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1992-11-08

---
 pc/l.s        |  41 +++++++++++++-
 pc/vga.c      | 146 +++++++++++++++++++++++++++++++++++---------------
 port/devbit.c |   6 +--
 3 files changed, 145 insertions(+), 48 deletions(-)

diff --git a/pc/l.s b/pc/l.s
index 9492a7ba1f98e50496e6435f18daf49aec85a5c1..87374d4bdd2f6204f78203f6f3e79e18f4039987 100644
--- a/pc/l.s
+++ b/pc/l.s
@@ -635,7 +635,9 @@ TEXT	config(SB),$0
 	RET
 
 /*
- *  copy bytes to screen memory for ldepth 0 screen
+ *  copy bitmap changes to screen memory for ldepth 0 screen
+ *  reverse the bits since the screen is big-endian
+ *  and the bitmaps are little.
  */
 TEXT	l0update(SB),$0
 	XORL	AX,AX
@@ -644,7 +646,42 @@ TEXT	l0update(SB),$0
 	MOVL	to+4(FP),DX
 l00:
 	MOVB	-1(BX)(CX*1),AL
-	MOVB	cswizzle(SB)(AX*1),AL
+	MOVB	bitrevtab(SB)(AX*1),AL
 	MOVB	AL,-1(DX)(CX*1)
 	LOOP	l00
 	RET
+
+#define SRX	0x3C4		/* index to sequence registers */
+#define	SR	0x3C5		/* sequence registers */
+#define Smmask	0x02		/*  map mask */
+
+/*
+ *  same as l0update but for ldepth 1 (2 bit plane) screens
+ */
+TEXT	l1update(SB),$0
+	MOVL	from+0(FP),SI
+	MOVL	to+4(FP),DI
+	MOVL	len+8(FP),CX
+l10:
+	XORL	DX,DX
+	MOVB	-2(SI)(CX*2),DL		/* high order nibbles */
+	MOVW	l1revsep(SB)(DX*2),BX
+	SHLW	$4,BX
+	MOVB	-1(SI)(CX*2),DL		/* low order nibbles */
+	ORW	l1revsep(SB)(DX*2),BX
+	MOVB	$(Smmask),AL		/* write hi order bits to bit planes 0 & 2 */
+	MOVW	$(SRX),DX
+	OUTB
+	MOVB	$0xA,AL
+	MOVW	$(SR),DX
+	OUTB
+	MOVB	BH,-1(DI)(CX*1)
+	MOVB	$(Smmask),AL		/* write lo order bits to bit planes 1 & 3 */
+	MOVW	$(SRX),DX
+	OUTB
+	MOVB	$0x5,AL
+	MOVW	$(SR),DX
+	OUTB
+	MOVB	BL,-1(DI)(CX*1)
+	LOOP	l10
+	RET
diff --git a/pc/vga.c b/pc/vga.c
index 8038d8776365802dd2f719c7f25119e501cd26ba..a31944d6b4c0007370923d2818aed171f9d60f33 100644
--- a/pc/vga.c
+++ b/pc/vga.c
@@ -327,6 +327,59 @@ mbbpt(Point p)
 		mbb.max.y = p.y+1;
 }
 
+/*
+ *  copy litte endian soft screen to big endian hard screen
+ */
+void
+screenupdate(void)
+{
+	uchar *sp, *hp;
+	int y, len, incs, inch;
+	Rectangle r;
+
+	r = mbb;
+	mbb = NULLMBB;
+
+	if(Dy(r) < 0)
+		return;
+
+	if(r.min.x < 0)
+		r.min.x = 0;
+	if(r.min.y < 0)
+		r.min.y = 0;
+	if(r.max.x > gscreen.r.max.x)
+		r.max.x = gscreen.r.max.x;
+	if(r.max.y > gscreen.r.max.y)
+		r.max.y = gscreen.r.max.y;
+
+	sp = (uchar*)gaddr(&gscreen, r.min);
+	hp = (uchar*)gaddr(&vgascreen, r.min);
+	len = (r.max.x + 31)/32 - r.min.x/32;
+	len *= BY2WD;
+	if(len <= 0)
+		return;
+
+	incs = gscreen.width * BY2WD;
+	inch = vgascreen.width * BY2WD;
+
+	switch(gscreen.ldepth){
+	case 0:
+		for (y = r.min.y; y < r.max.y; y++){
+			l0update(sp, hp, len);
+			sp += incs;
+			hp += inch;
+		}
+		break;
+	case 1:
+		for (y = r.min.y; y < r.max.y; y++){
+			l1update(sp, hp, len);
+			sp += incs;
+			hp += inch;
+		}
+		break;
+	}
+}
+
 void
 screenputnl(void)
 {
@@ -394,49 +447,6 @@ screenbits(void)
 }
 
 
-/*
- *  copy litte endian soft screen to big endian hard screen
- */
-void
-screenupdate(void)
-{
-	uchar *sp, *hp, *se;
-	int y, len, inc;
-	Rectangle r;
-
-	r = mbb;
-	mbb = NULLMBB;
-
-	if(Dy(r) < 0)
-		return;
-
-	if(r.min.x < 0)
-		r.min.x = 0;
-	if(r.min.y < 0)
-		r.min.y = 0;
-	if(r.max.x > gscreen.r.max.x)
-		r.max.x = gscreen.r.max.x;
-	if(r.max.y > gscreen.r.max.y)
-		r.max.y = gscreen.r.max.y;
-
-	sp = (uchar*)gaddr(&gscreen, r.min);
-	hp = (uchar*)gaddr(&vgascreen, r.min);
-
-	len = (r.max.x * (1<<gscreen.ldepth) + 31)/32
-		- (r.min.x * (1<<gscreen.ldepth))/32;
-	len *= BY2WD;
-	if(len <= 0)
-		return;
-
-	inc = gscreen.width * BY2WD - len;
-
-	for (y = r.min.y; y < r.max.y; y++){
-		l0update(sp, hp, len);
-		sp += inc+len;
-		hp += inc+len;
-	}
-}
-
 void
 mousescreenupdate(void)
 {
@@ -512,3 +522,53 @@ bigcursor(void)
 	bitreverse(arrow.set, 2*16);
 	bitreverse(arrow.clr, 2*16);
 }
+
+/*
+ *  Table for separating and reversing bits in a ldepth 1 bitmap.
+ *  This aids in coverting a little endian ldepth 1 bitmap into the
+ *  2 big-endian ldepth 0 bitmaps used for the VGA bit planes.
+ *
+ *	if the bits in uchar x are labeled
+ *		76543210
+ *	then l1revsep[x] yields a ushort with bits
+ *		____0246____1357
+ *	where _ represents a bit whose value is 0.
+ *
+ *  This table is used by l1update() in l.s.  l1update is implemented
+ *  in assembler for speed (yech).
+ *
+ */
+ushort l1revsep[] = {
+	0x0000,	0x0800,	0x0008,	0x0808,	0x0400,	0x0c00,	0x0408,	0x0c08,
+	0x0004,	0x0804,	0x000c,	0x080c,	0x0404,	0x0c04,	0x040c,	0x0c0c,
+	0x0200,	0x0a00,	0x0208,	0x0a08,	0x0600,	0x0e00,	0x0608,	0x0e08,
+	0x0204,	0x0a04,	0x020c,	0x0a0c,	0x0604,	0x0e04,	0x060c,	0x0e0c,
+	0x0002,	0x0802,	0x000a,	0x080a,	0x0402,	0x0c02,	0x040a,	0x0c0a,
+	0x0006,	0x0806,	0x000e,	0x080e,	0x0406,	0x0c06,	0x040e,	0x0c0e,
+	0x0202,	0x0a02,	0x020a,	0x0a0a,	0x0602,	0x0e02,	0x060a,	0x0e0a,
+	0x0206,	0x0a06,	0x020e,	0x0a0e,	0x0606,	0x0e06,	0x060e,	0x0e0e,
+	0x0100,	0x0900,	0x0108,	0x0908,	0x0500,	0x0d00,	0x0508,	0x0d08,
+	0x0104,	0x0904,	0x010c,	0x090c,	0x0504,	0x0d04,	0x050c,	0x0d0c,
+	0x0300,	0x0b00,	0x0308,	0x0b08,	0x0700,	0x0f00,	0x0708,	0x0f08,
+	0x0304,	0x0b04,	0x030c,	0x0b0c,	0x0704,	0x0f04,	0x070c,	0x0f0c,
+	0x0102,	0x0902,	0x010a,	0x090a,	0x0502,	0x0d02,	0x050a,	0x0d0a,
+	0x0106,	0x0906,	0x010e,	0x090e,	0x0506,	0x0d06,	0x050e,	0x0d0e,
+	0x0302,	0x0b02,	0x030a,	0x0b0a,	0x0702,	0x0f02,	0x070a,	0x0f0a,
+	0x0306,	0x0b06,	0x030e,	0x0b0e,	0x0706,	0x0f06,	0x070e,	0x0f0e,
+	0x0001,	0x0801,	0x0009,	0x0809,	0x0401,	0x0c01,	0x0409,	0x0c09,
+	0x0005,	0x0805,	0x000d,	0x080d,	0x0405,	0x0c05,	0x040d,	0x0c0d,
+	0x0201,	0x0a01,	0x0209,	0x0a09,	0x0601,	0x0e01,	0x0609,	0x0e09,
+	0x0205,	0x0a05,	0x020d,	0x0a0d,	0x0605,	0x0e05,	0x060d,	0x0e0d,
+	0x0003,	0x0803,	0x000b,	0x080b,	0x0403,	0x0c03,	0x040b,	0x0c0b,
+	0x0007,	0x0807,	0x000f,	0x080f,	0x0407,	0x0c07,	0x040f,	0x0c0f,
+	0x0203,	0x0a03,	0x020b,	0x0a0b,	0x0603,	0x0e03,	0x060b,	0x0e0b,
+	0x0207,	0x0a07,	0x020f,	0x0a0f,	0x0607,	0x0e07,	0x060f,	0x0e0f,
+	0x0101,	0x0901,	0x0109,	0x0909,	0x0501,	0x0d01,	0x0509,	0x0d09,
+	0x0105,	0x0905,	0x010d,	0x090d,	0x0505,	0x0d05,	0x050d,	0x0d0d,
+	0x0301,	0x0b01,	0x0309,	0x0b09,	0x0701,	0x0f01,	0x0709,	0x0f09,
+	0x0305,	0x0b05,	0x030d,	0x0b0d,	0x0705,	0x0f05,	0x070d,	0x0f0d,
+	0x0103,	0x0903,	0x010b,	0x090b,	0x0503,	0x0d03,	0x050b,	0x0d0b,
+	0x0107,	0x0907,	0x010f,	0x090f,	0x0507,	0x0d07,	0x050f,	0x0d0f,
+	0x0303,	0x0b03,	0x030b,	0x0b0b,	0x0703,	0x0f03,	0x070b,	0x0f0b,
+	0x0307,	0x0b07,	0x030f,	0x0b0f,	0x0707,	0x0f07,	0x070f,	0x0f0f,
+};
diff --git a/port/devbit.c b/port/devbit.c
index 8c5078d3b734ff9e56fb44aa2121a5fe18e8beaa..dc9a13c3ed9d6daedc4fac1f6dd1224d1e5efbcf 100644
--- a/port/devbit.c
+++ b/port/devbit.c
@@ -2104,9 +2104,9 @@ mousechanged(void *m)
 }
 
 /*
- *  swizzle a bitmap
+ *  reverse the bits in a bitmap (converting between little & big endian)
  */
-uchar cswizzle[] = {
+uchar bitrevtab[] = {
 	0x00,	0x80,	0x40,	0xc0,	0x20,	0xa0,	0x60,	0xe0,
 	0x10,	0x90,	0x50,	0xd0,	0x30,	0xb0,	0x70,	0xf0,
 	0x08,	0x88,	0x48,	0xc8,	0x28,	0xa8,	0x68,	0xe8,
@@ -2148,5 +2148,5 @@ bitreverse(uchar *p, int l)
 
 	e = p + l;
 	for(; p < e; p++)
-		*p = cswizzle[*p];
+		*p = bitrevtab[*p];
 }