From 971e51eebbf088f1ac590da1fc57e803eb1ee8cf Mon Sep 17 00:00:00 2001
From: Peter Fors <peter.fors@mindkiller.com>
Date: Wed, 2 Apr 2025 13:17:35 +0200
Subject: add mapper #66 (GXROM)

---
 mapper.c       | 51 ++++++++++++++++++++++++++++++++-------------------
 mapper.h       |  2 ++
 mapper_gxrom.c | 27 +++++++++++++++++++++++++++
 mapper_gxrom.h |  5 +++++
 mknes.c        |  6 ++++--
 mknes.h        |  2 +-
 6 files changed, 71 insertions(+), 22 deletions(-)
 create mode 100644 mapper.h
 create mode 100644 mapper_gxrom.c
 create mode 100644 mapper_gxrom.h

diff --git a/mapper.c b/mapper.c
index 0b595ff..4fb8346 100644
--- a/mapper.c
+++ b/mapper.c
@@ -3,27 +3,40 @@
 #include "mapper_nrom.c"
 // #include "mapper_mmc1.c"
 // #include "mapper_uxrom.c"
+#include "mapper_gxrom.c"
 
-static void mapper_setup(struct nes_state *state) {
-	printf("Mapper: %d\n", state->ines.mapper);
-	switch(state->ines.mapper) {
-		case 0:
-			state->mapper.read  = mapper_nrom_read;
-			state->mapper.write = mapper_nrom_write;
-			state->mapper.tick  = mapper_nrom_tick;
-			state->mapper.init  = mapper_nrom_init;
-			state->mapper.init(state);
-			break;
+struct mapper_entry {
+	int id;
+	uint8_t (*read)(struct nes_state *state, uint32_t addr);
+	void (*write)(struct nes_state *state, uint32_t addr, uint8_t value);
+	void (*tick)(struct nes_state *state);
+	void (*init)(struct nes_state *state);
+};
 
-		default:
-			// fallback: NROM-compatible
-			state->mapper.read  = mapper_nrom_read;
-			state->mapper.write = mapper_nrom_write;
-			state->mapper.tick  = mapper_nrom_tick;
-			state->mapper.init  = mapper_nrom_init;
+static struct mapper_entry mapper_table[] = {
+	{ 0,  mapper_nrom_read,  mapper_nrom_write,  mapper_nrom_tick,  mapper_nrom_init },
+	{ 66, mapper_66_read,    mapper_66_write,    mapper_66_tick,    mapper_66_init },
+	// { 1, mapper_mmc1_read, ... }, etc
+};
+
+static void mapper_setup(struct nes_state *state) {
+	uint32_t mapper = state->ines.mapper;
+	for(uint32_t i = 0; i < sizeof(mapper_table)/sizeof(mapper_table[0]); i++) {
+		if(mapper_table[i].id == mapper) {
+printf("%d\n", mapper);
+			state->mapper.read  = mapper_table[i].read;
+			state->mapper.write = mapper_table[i].write;
+			state->mapper.tick  = mapper_table[i].tick;
+			state->mapper.init  = mapper_table[i].init;
 			state->mapper.init(state);
-			break;
+			return;
+		}
 	}
-}
-
 
+	printf("Unsupported mapper %d, falling back to NROM\n", mapper);
+	state->mapper.read  = mapper_nrom_read;
+	state->mapper.write = mapper_nrom_write;
+	state->mapper.tick  = mapper_nrom_tick;
+	state->mapper.init  = mapper_nrom_init;
+	state->mapper.init(state);
+}
diff --git a/mapper.h b/mapper.h
new file mode 100644
index 0000000..eb6c158
--- /dev/null
+++ b/mapper.h
@@ -0,0 +1,2 @@
+
+#include "mapper_gxrom.h"
diff --git a/mapper_gxrom.c b/mapper_gxrom.c
new file mode 100644
index 0000000..e03f9d2
--- /dev/null
+++ b/mapper_gxrom.c
@@ -0,0 +1,27 @@
+
+static void mapper_66_init(struct nes_state *state) {
+	state->map.gxrom.prg_offset = 0;
+	state->map.gxrom.chr_offset = 0;
+}
+
+static uint8_t mapper_66_read(struct nes_state *state, uint32_t addr) {
+	if(addr >= 0x8000) {
+		uint32_t base = state->map.gxrom.prg_offset;
+		return state->rom[base + (addr - 0x8000)];
+	}
+	return 0;
+}
+
+static void mapper_66_write(struct nes_state *state, uint32_t addr, uint8_t value) {
+	if(addr >= 0x8000) {
+		uint32_t prg_bank = (value >> 4) & 3;
+		uint32_t chr_bank = (value >> 0) & 3;
+
+		state->map.gxrom.prg_offset = prg_bank * 0x8000;
+		state->map.gxrom.chr_offset = chr_bank * 0x2000;
+	}
+}
+
+static void mapper_66_tick(struct nes_state *state) {
+	// No IRQ or timing logic needed
+}
diff --git a/mapper_gxrom.h b/mapper_gxrom.h
new file mode 100644
index 0000000..757ec16
--- /dev/null
+++ b/mapper_gxrom.h
@@ -0,0 +1,5 @@
+
+struct gxrom_mapper {
+	uint32_t prg_offset;
+	uint32_t chr_offset;
+};
diff --git a/mknes.c b/mknes.c
index 6150ba4..d94c868 100644
--- a/mknes.c
+++ b/mknes.c
@@ -2,6 +2,8 @@
 
 #include "base.c"
 
+#include "mapper.h"
+
 #include "mknes.h"
 // #include "apu.c"
 #include "ppu.c"
@@ -68,12 +70,12 @@ static void init_callback(void) {
 	ppu_reset(&nstate);
 	// ines2_load(&nstate, "data/nrom/10-Yard Fight (USA, Europe).nes");
 	// ines2_load(&nstate, "data/nrom/Balloon Fight (USA).nes");
-	// ines2_load(&nstate, "data/nrom/Excitebike (Japan, USA).nes");
+	ines2_load(&nstate, "data/nrom/Excitebike (Japan, USA).nes");
 	// ines2_load(&nstate, "data/nrom/Ice Climber (USA, Europe, Korea).nes");
 	// ines2_load(&nstate, "data/nrom/Kung Fu (Japan, USA).nes");
 	// ines2_load(&nstate, "data/nrom/Super Mario Bros. (World) (HVC-SM).nes");
 	// ines2_load(&nstate, "data/nrom/Urban Champion (World).nes");
-	ines2_load(&nstate, "data/nrom/Wrecking Crew (World).nes");
+	// ines2_load(&nstate, "data/nrom/Wrecking Crew (World).nes");
 	// ines2_load(&nstate, "data/nrom/scanline.nes");
 	// ines2_load(&nstate, "data/nrom/Sayoonara!.NES");
 	// ines2_load(&nstate, "data/nrom/raster_demos/RasterChromaLuma.NES");
diff --git a/mknes.h b/mknes.h
index 8ed7554..90bb58c 100644
--- a/mknes.h
+++ b/mknes.h
@@ -127,7 +127,7 @@ struct mapper {
 };
 
 union mapper_data {
-	// struct nrom_mapper nrom;
+	struct gxrom_mapper gxrom;
 	// struct mmc1_mapper mmc1;
 	// ... others
 };
-- 
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