From c7adf21a4c52bd78428a93cdbaf25c52b03783ba Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Fri, 16 Feb 2024 22:22:10 +0100
Subject: Allow the user to reset the emulator

---
 src/TODO            |  1 -
 src/ahoy/config.h   |  4 ++--
 src/ahoy/emulator.c | 20 +++++++++++++-------
 src/ahoy/emulator.h |  1 +
 src/ahoy/gui.c      |  8 ++++----
 src/ahoy/main.c     |  5 ++---
 6 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/src/TODO b/src/TODO
index 87bc4da..bade6b3 100644
--- a/src/TODO
+++ b/src/TODO
@@ -12,7 +12,6 @@ ahoy:
 	— Savestates
 	— Scanlines
 	— Other cool visual effects
-	— Machine reset
 c8c:
 	— Implement the C8 compiler
 	— Write assembly to stdout, allowing for such constructions as
diff --git a/src/ahoy/config.h b/src/ahoy/config.h
index 106382f..6fa60c2 100644
--- a/src/ahoy/config.h
+++ b/src/ahoy/config.h
@@ -4,8 +4,8 @@
 #include <stdint.h>
 
 struct config {
-	/* Valid ranges are 0–UINT16_MAX.  >UINT16_MAX is for random seed. */
-	uint32_t seed;
+	bool seeded;
+	uint16_t seed;
 	unsigned cpu_hz;
 };
 
diff --git a/src/ahoy/emulator.c b/src/ahoy/emulator.c
index f774b54..3b6544b 100644
--- a/src/ahoy/emulator.c
+++ b/src/ahoy/emulator.c
@@ -43,24 +43,30 @@ static uint8_t mem[MEM_TOTAL] = {
 void
 emuinit(struct u8view prog, const char *fn)
 {
-	struct timespec tp;
-
 	filename = fn;
-
 	if (prog.len > MEM_FREE) {
 		diex("%s: binary of size %.1f KiB exceeds %d B maximum", filename,
 		     (double)prog.len / 1024, MEM_FREE);
 	}
+	memcpy(mem + MEM_RESERVED, prog.p, prog.len);
+	emureset();
+}
 
+void
+emureset(void)
+{
+	struct timespec tp;
+
+	memset(&c8, 0, sizeof(c8));
 	c8.PC = MEM_RESERVED;
-	memcpy(mem + c8.PC, prog.p, prog.len);
 
-	if (cfg.seed > UINT16_MAX) {
+	if (cfg.seeded)
+		srand(cfg.seed);
+	else {
 		if (clock_gettime(CLOCK_REALTIME, &tp) == -1)
 			die("clock_gettime");
 		srand((tp.tv_sec ^ tp.tv_nsec) & UINT16_MAX);
-	} else
-		srand(cfg.seed);
+	}
 }
 
 void
diff --git a/src/ahoy/emulator.h b/src/ahoy/emulator.h
index 24aa8ce..33618da 100644
--- a/src/ahoy/emulator.h
+++ b/src/ahoy/emulator.h
@@ -26,6 +26,7 @@ struct chip8 {
 
 void emuinit(struct u8view, const char *);
 void emutick(void);
+void emureset(void);
 
 extern struct chip8 c8;
 
diff --git a/src/ahoy/gui.c b/src/ahoy/gui.c
index a052a39..072d5b9 100644
--- a/src/ahoy/gui.c
+++ b/src/ahoy/gui.c
@@ -128,10 +128,10 @@ readkb(void)
 				gs = gs == GUI_RUNNING ? GUI_PAUSED : GUI_RUNNING;
 				break;
 
-			// case SDLK_EQUALS:
-			// 	init_chip8(chip8, *config, chip8->rom_name);
-			// 	break;
-			//
+			case SDLK_EQUALS:
+				emureset();
+				break;
+
 			// case SDLK_j:
 			// 	// 'j': Decrease color lerp rate
 			// 	if (config->color_lerp_rate > 0.1)
diff --git a/src/ahoy/main.c b/src/ahoy/main.c
index fc737e6..857185b 100644
--- a/src/ahoy/main.c
+++ b/src/ahoy/main.c
@@ -52,9 +52,7 @@ STRTOX(uint16_t, u16)
 [[noreturn]] static void usage(void);
 static void run(int, const char *);
 
-struct config cfg = {
-	.seed = UINT16_MAX + 1,
-};
+struct config cfg;
 static const char *argv0;
 
 void
@@ -114,6 +112,7 @@ main(int argc, char **argv)
 			break;
 		case 's':
 			NUMERIC_ARG(uint16_t, UINT16_MAX, PRIu16, strtou16, seed, "seed");
+			cfg.seeded = true;
 			break;
 		default:
 			usage();
-- 
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