From 7d60741c1393ebc0c572891cfeb19a25c4579ed6 Mon Sep 17 00:00:00 2001
From: Daniel Jones <admin@danieljon.es>
Date: Mon, 17 Aug 2020 15:16:02 +0930
Subject: sprite drawing basic implementation

begin implementing sprite drawing, currently draws the chip8 fontset well, no idead about other sprites yet
---
 chip8.c | 38 +++++++++++++++++++++++++++++++++++++-
 chip8.h |  3 ++-
 main.c  | 25 +++++++++++++++++++++++--
 3 files changed, 62 insertions(+), 4 deletions(-)

diff --git a/chip8.c b/chip8.c
index 2ce911f..db2efd2 100644
--- a/chip8.c
+++ b/chip8.c
@@ -71,7 +71,7 @@ chip8_init()
 	draw_flag = 1;		// draw by default i guess
 	delay_timer = 0;
 	sound_timer = 0;
-	srand(time(NULL));	// seed rng
+	srand(time(NULL));
 
 	/* load font into memory at 0x00: we have 0x00 to 0x1FF free for anything we want */
 	//TODO: add whole alphabet, then can write a rom to write strings or something
@@ -80,3 +80,39 @@ chip8_init()
 		memory[0x0 + i] = chip8_fontset[i];
 	}
 }
+
+void
+chip8_draw_sprite(int startx, int starty, uint8_t mem, uint8_t size)
+{
+	/*
+	 * draw sprite located at loc of height size at startx,starty
+	 */
+
+	uint8_t byte = 0;
+	uint8_t mask = 0x1;
+	uint8_t destbit = 0x0;
+	for (uint8_t byteoffset = 0; byteoffset < size; byteoffset++)
+	{
+		/* loop through each byte from mem to mem+size */
+		byte = memory[mem+byteoffset];
+		int bit = 0;
+		for (mask = 0x80; mask != 0; mask >>= 1)
+		{
+			if (byte&mask)
+			{
+				destbit = 1;
+				video[WIDTH*starty+(startx+bit)] = 0xFFFFFF;
+			}
+			else
+			{
+				destbit = 0;
+				video[WIDTH*starty+(startx+bit)] = 0x0;
+			}
+			printf("%d", destbit);
+			bit++;
+		}
+		starty++;
+		puts("");
+	}
+	puts("---");
+}
diff --git a/chip8.h b/chip8.h
index 4faa6e4..6018d40 100644
--- a/chip8.h
+++ b/chip8.h
@@ -13,9 +13,10 @@
 #define KEY_SIZE 15
 #define MEMORY_SIZE 4096
 #define STACK_SIZE 16
-#define MAX_ROM_SIZE 0x1000 - 0x200 // memory size - reseved memory
+#define MAX_ROM_SIZE 0x1000 - 0x200 // memory size - reserved memory
 
 int load_rom();
 void chip8_init();
+void chip8_draw_sprite(int startx, int starty, uint8_t mem, uint8_t size);
 
 #endif
diff --git a/main.c b/main.c
index a3b9539..d549b25 100644
--- a/main.c
+++ b/main.c
@@ -9,6 +9,7 @@
  * http://www.multigesture.net/articles/how-to-write-an-emulator-chip-8-interpreter/
  * http://mattmik.com/files/chip8/mastering/chip8.html (lots of info)
  * http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#0.1
+ * http://www.emulator101.com/chip-8-sprites.html
  */
 
 #define VIDEO_SCALE 10
@@ -24,6 +25,7 @@ void quit();
 void usage(char *);
 
 extern uint32_t video[WIDTH*HEIGHT];
+extern int draw_flag;
 
 void
 usage(char *program)
@@ -54,7 +56,7 @@ void
 update_video()
 {
 	static int count = 0;
-	printf("frame %d\n", count++);
+	//printf("frame %d\n", count++);
 	/*
 	for (uint32_t i = 0 ;i < WIDTH*HEIGHT; i++)
 	{
@@ -66,7 +68,6 @@ update_video()
 	video[2] = (255<<16);
 	*/
 
-	toggle_pixel(0, 0);
 	SDL_UpdateTexture(texture, NULL, video, sizeof(video[0])*WIDTH);
 	SDL_RenderClear(renderer);
 	SDL_RenderCopy(renderer, texture, NULL, NULL);
@@ -106,7 +107,27 @@ int main(int argc, char *argv[])
 	const int frame_delay = 1000/fps;
 	uint32_t  frame_start;
 	uint32_t frame_time;
+
 	int do_quit = 0;
+	chip8_draw_sprite(0, 0, 0xD*5, 0x5);
+	chip8_draw_sprite(5, 0, 0xE*5, 0x5);
+	chip8_draw_sprite(10, 0, 0xA*5, 0x5);
+	chip8_draw_sprite(15, 0, 0xD*5, 0x5);
+	chip8_draw_sprite(20, 0, 0xB*5, 0x5);
+	chip8_draw_sprite(25, 0, 0xE*5, 0x5);
+	chip8_draw_sprite(30, 0, 0xE*5, 0x5);
+	chip8_draw_sprite(35, 0, 0xf*5, 0x5);
+
+	chip8_draw_sprite(0,  9, 0xD*5, 0x5);
+	chip8_draw_sprite(5,  9, 0xE*5, 0x5);
+	chip8_draw_sprite(10, 9, 0xA*5, 0x5);
+	chip8_draw_sprite(15, 9, 0xD*5, 0x5);
+	chip8_draw_sprite(20, 9, 0xB*5, 0x5);
+	chip8_draw_sprite(25, 9, 0xE*5, 0x5);
+	chip8_draw_sprite(30, 9, 0xE*5, 0x5);
+	chip8_draw_sprite(35, 9, 0xf*5, 0x5);
+
+
 	while(!do_quit)
 	{
 		frame_start = SDL_GetTicks();
-- 
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