replace magic numbers with constants

3 files changed, 21 insertions, 13 deletions

diff --git a/chip8.c b/chip8.c
index b6d52eb..9933096 100644
--- a/chip8.c
+++ b/chip8.c
@@ -3,7 +3,7 @@
 uint16_t opcode;		// 2 byte opcode
 uint8_t key[KEY_SIZE]; 		// hex key input
 uint32_t video[WIDTH*HEIGHT]; 	// video memory TODO: video should be 8 bit not 32
-uint8_t V[16];			// registers - 0x0 to 0xF
+uint8_t V[REGISTER_COUNT];	// registers - 0x0 to 0xF
 uint16_t I;			// special I register, stores addresses
 uint16_t PC;			// program counter
 uint8_t SP;			// stack pointer
@@ -48,7 +48,7 @@ load_rom(char *rom)
 	}
 
 	/* read a maximum of MAX_ROM_SIZE bytes into memory starting after the reserved memory */
-	fread(&memory[0x200], 1, MAX_ROM_SIZE, romfile);
+	fread(&memory[PROGRAM_START], 1, MAX_ROM_SIZE, romfile);
 
 	fclose(romfile);
 	return ret;
@@ -58,13 +58,13 @@ void
 chip8_init()
 {
 	/* clear everything and set sane defaults */
-	memset(key, 0, sizeof(uint8_t) * 15);
+	memset(key, 0, sizeof(uint8_t) * KEY_SIZE);
 	memset(video, 0, (WIDTH*HEIGHT) * sizeof(uint32_t));
-	memset(V, 0, sizeof(uint8_t) * 16);
+	memset(V, 0, sizeof(uint8_t) * REGISTER_COUNT);
 	memset(stack, 0, (STACK_SIZE) * sizeof(uint16_t));
 	memset(memory, 0, sizeof(uint8_t) * MEMORY_SIZE);
 
-	PC = 0x200; 		// set program counter to where roms are stored
+	PC = PROGRAM_START; 	// set program counter to where roms are stored
 	opcode = 0;
 	I = 0;
 	SP = 0;
@@ -75,16 +75,16 @@ chip8_init()
 
 	/* 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
-	for (uint8_t i = 0; i < 80; i++)
+	for (uint8_t i = 0; i < FONT_BYTE_SIZE; i++)
 	{
-		memory[0x0 + i] = chip8_fontset[i];
+		memory[ + i] = chip8_fontset[i];
 	}
 
 	uint8_t sinv[] = {0xBA, 0x7C, 0xD6, 0xFE, 0x54, 0xAA};
 	// temp
-	for (uint8_t i = 0; i < 6; i++)
+	for (uint8_t i = 0; i <= FONT_WIDTH; i++)
 	{
-		memory[0x200+i] = sinv[i];
+		memory[PROGRAM_START+i] = sinv[i];
 	}
 }
 
@@ -103,7 +103,7 @@ chip8_draw_sprite(int startx, int starty, uint16_t mem, uint8_t size)
 		/* loop through each byte from mem to mem+size */
 		byte = memory[mem+byteoffset];
 		int bit = 0;
-		for (mask = 0x80; mask != 0; mask >>= 1)
+		for (mask = BYTE_MASK; mask != 0; mask >>= 1)
 		{
 			if (byte & mask)
 			{
@@ -113,7 +113,7 @@ chip8_draw_sprite(int startx, int starty, uint16_t mem, uint8_t size)
 					/* if the video bit is already set, we need to set the collision register */
 					V[0xF] = 1;
 				}
-				video[pixel] ^= 0xFFFFFF;
+				video[pixel] ^= PIXEL_COLOR;
 			}
 			bit++;
 		}
diff --git a/chip8.h b/chip8.h
index e16274d..6779567 100644
--- a/chip8.h
+++ b/chip8.h
@@ -12,8 +12,14 @@
 #define HEIGHT 32
 #define KEY_SIZE 15
 #define MEMORY_SIZE 4096
+#define REGISTER_COUNT 16
 #define STACK_SIZE 16
 #define MAX_ROM_SIZE 0x1000 - 0x200 // memory size - reserved memory
+#define PROGRAM_START 0x200
+#define FONT_WIDTH 5
+#define FONT_BYTE_SIZE 80
+#define BYTE_MASK 0x80
+#define PIXEL_COLOR 0xFFFFFF
 
 int load_rom();
 void chip8_init();
diff --git a/main.c b/main.c
index c6fb639..9a81c31 100644
--- a/main.c
+++ b/main.c
@@ -45,7 +45,6 @@ quit()
 	SDL_DestroyRenderer(renderer);
 	SDL_DestroyWindow(window);
 	SDL_Quit();
-
 }
 
 void
@@ -72,7 +71,7 @@ toggle_pixel(int x, int y)
 	// TODO: clean
 	uint32_t dos = video[WIDTH*y+x];
 	if (dos <= 0)
-		video[WIDTH*y+x] = (255<<16)|(255<<8)|255;
+		video[WIDTH*y+x] = PIXEL_COLOR;
 	else
 		video[WIDTH*y+x] = 0;
 }
@@ -207,7 +206,10 @@ int main(int argc, char *argv[])
 		chip8_cycle();
 
 		if (draw_flag)
+		{
 			update_video();
+			draw_flag = 0;
+		}
 
 		frame_time = SDL_GetTicks() - frame_start;
 		if (frame_delay > frame_time)