From c0e42f132291542d8c275efea5fc09ede4f83ee9 Mon Sep 17 00:00:00 2001
From: Andrew Alderwick <andrew@alderwick.co.uk>
Date: Mon, 20 Sep 2021 22:32:42 +0100
Subject: [PATCH] Switched to faster unsigned ints for PPU memory

---
 src/devices/ppu.c | 17 ++++++++---------
 src/devices/ppu.h | 12 ++++++++----
 src/uxnemu.c      |  5 +++--
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/devices/ppu.c b/src/devices/ppu.c
index f5d50dc..0ddfa91 100644
--- a/src/devices/ppu.c
+++ b/src/devices/ppu.c
@@ -23,22 +23,22 @@ static void
 ppu_clear(Ppu *p)
 {
 	int i;
-	for(i = 0; i < p->width / 2 * p->height; ++i)
+	for(i = 0; i < p->stride * p->height; ++i)
 		p->dat[i] = 0;
 }
 
-int
+unsigned int
 ppu_pixel(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 color)
 {
-	unsigned int i = (x + y * p->width) / 2, shift = (x % 2) * 4;
-	int ret = p->dat[i];
+	unsigned int i = x / PPW + y * p->stride, shift = x % PPW * 4;
+	unsigned int ret = p->dat[i];
 	if(fg) shift += 2;
 	p->dat[i] &= ~(3 << shift);
 	p->dat[i] |= color << shift;
 	return ret ^ p->dat[i];
 }
 
-int
+unsigned int
 ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)
 {
 	Uint16 v, h;
@@ -56,7 +56,7 @@ ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 f
 	return ret;
 }
 
-int
+unsigned int
 ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy)
 {
 	Uint16 v, h;
@@ -81,11 +81,10 @@ ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 f
 int
 ppu_set_size(Ppu *p, Uint16 width, Uint16 height)
 {
-	/* round width up to nearest multiple of 2 */
-	width += width % 2;
 	p->width = width;
+	p->stride = (width + PPW - 1) / PPW;
 	p->height = height;
-	p->dat = realloc(p->dat, p->width / 2 * p->height);
+	p->dat = realloc(p->dat, p->stride * p->height * sizeof(unsigned int));
 	if(p->dat == NULL) return 0;
 	ppu_clear(p);
 	return 1;
diff --git a/src/devices/ppu.h b/src/devices/ppu.h
index 3c056f0..abb241a 100644
--- a/src/devices/ppu.h
+++ b/src/devices/ppu.h
@@ -13,16 +13,20 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 WITH REGARD TO THIS SOFTWARE.
 */
 
+/* pixels per word in ppu.dat */
+
+#define PPW (sizeof(unsigned int) * 2)
+
 typedef unsigned char Uint8;
 typedef unsigned short Uint16;
 typedef unsigned int Uint32;
 
 typedef struct Ppu {
 	Uint16 width, height;
-	Uint8 *dat;
+	unsigned int *dat, stride;
 } Ppu;
 
 int ppu_set_size(Ppu *p, Uint16 width, Uint16 height);
-int ppu_pixel(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 color);
-int ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
-int ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
+unsigned int ppu_pixel(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 color);
+unsigned int ppu_1bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
+unsigned int ppu_2bpp(Ppu *p, int fg, Uint16 x, Uint16 y, Uint8 *sprite, Uint8 color, Uint8 flipx, Uint8 flipy);
diff --git a/src/uxnemu.c b/src/uxnemu.c
index 0aad157..1c88ef1 100644
--- a/src/uxnemu.c
+++ b/src/uxnemu.c
@@ -38,7 +38,8 @@ static Apu apu[POLYPHONY];
 static Device *devsystem, *devscreen, *devmouse, *devctrl, *devaudio0, *devconsole;
 static Uint32 *ppu_screen, stdin_event, audio0_event, palette[4];
 
-static Uint8 zoom = 1, reqdraw = 0;
+static Uint8 zoom = 1;
+static unsigned int reqdraw = 0;
 
 static Uint8 font[][8] = {
 	{0x00, 0x7c, 0x82, 0x82, 0x82, 0x82, 0x82, 0x7c},
@@ -114,7 +115,7 @@ inspect(Ppu *p, Uint8 *stack, Uint8 wptr, Uint8 rptr, Uint8 *memory)
 static Uint8
 get_pixel(int x, int y)
 {
-	unsigned int i = (x + y * ppu.width) / 2, shift = (x % 2) * 4;
+	unsigned int i = x / PPW + y * ppu.stride, shift = x % PPW * 4;
 	return (ppu.dat[i] >> shift) & 0xf;
 }