From 93fd16dcd4c66ed003363d6e7f0c70bd3d2de92c Mon Sep 17 00:00:00 2001
From: Peter Fors <peter.fors@mindkiller.com>
Date: Thu, 29 May 2025 21:41:13 +0200
Subject: rewrite of memory_read()

---
 memory.c | 16 +++++++++-------
 ppu.c    |  4 ++--
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/memory.c b/memory.c
index 096189b..1eaf489 100644
--- a/memory.c
+++ b/memory.c
@@ -6,26 +6,28 @@ static inline uint8_t memory_read(struct nes_state *state, uint32_t offset) {
 	ppu_tick(state);
 	// apu_tick(state);
 
+	uint8_t result = 0;
+
 	if(offset >= 0x8000) {	// MOST
-		return state->mapper_function.prg_rom_read(state, offset);
+		result = state->mapper_function.prg_rom_read(state, offset);
 
-	} else if((offset < 0x2000)) {	// SECOND
-		return state->ram[offset & 0x07ff];
+	} else if(offset < 0x2000) {	// SECOND
+		result = state->ram[offset & 0x07ff];
 
 	} else if(offset < 0x4000) {	// THIRD
-		return ppu_read(state, offset);
+		result = ppu_read(state, offset);
 
 	} else if(offset >= 0x6000) {
-		return state->mapper_function.prg_ram_read(state, offset);
+		result = state->mapper_function.prg_ram_read(state, offset);
 
 	} else if(offset == 0x4016 || offset == 0x4017) {
 		uint32_t index = offset & 1;
 		uint8_t value = (state->ppu.input_latch[index] >> state->ppu.input_bit[index]) & 1;
 		state->ppu.input_bit[index]++;
-		return value | 0x40;	// Bit 6 open bus high, bit 7 low
+		result = value | 0x40;	// Bit 6 open bus high, bit 7 low
 	}
 
-	return 0;
+	return result;
 }
 
 __attribute__((hot))
diff --git a/ppu.c b/ppu.c
index 8280265..570f3dd 100644
--- a/ppu.c
+++ b/ppu.c
@@ -28,7 +28,7 @@ __attribute__((hot))
 static inline void ppu_evaluate_sprites(struct nes_state *state) {
 	struct ppu_state *restrict ppu = &state->ppu;
 	uint8_t sprite_height = (ppu->reg_ctrl & 0x20) ? 16 : 8;
-	uint8_t n = 0;
+	uint32_t n = 0;
 
 	uint8_t * restrict src = ppu->oam;
 	uint8_t * restrict dst = ppu->secondary_oam;
@@ -47,7 +47,7 @@ static inline void ppu_evaluate_sprites(struct nes_state *state) {
 				dst += 4;
 				n++;
 			} else {
-				ppu->reg_status |= 0x20;
+				ppu->reg_status |= 0x20;		// NOTE(peter): sprite overflow
 				break;
 			}
 		}
-- 
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