1 files changed, 90 insertions, 0 deletions
diff --git a/ines2.c b/ines2.c
new file mode 100644
index 0000000..450c22e
--- /dev/null
+++ b/ines2.c
@@ -0,0 +1,90 @@
+
+
+
+// iNES header fields
+#define INES_HEADER_SIZE	16
+#define INES_PRG_SIZE_LSB	4
+#define INES_CHR_SIZE_LSB	5
+#define INES_FLAGS6		6
+#define INES_FLAGS7		7
+#define INES_PRG_CHR_MSB	9
+#define INES_CHR_EXP		8
+#define INES_PRG_EXP		9
+
+// Size units
+#define PRG_ROM_UNIT		16384
+#define CHR_ROM_UNIT		8192
+#define TRAINER_SIZE		512
+
+// Flag masks
+#define FLAG6_TRAINER		0x04
+#define FLAG6_FOUR_SCREEN	0x08
+#define FLAG6_VERTICAL_MIRROR	0x01
+
+// Mirroring modes
+#define MIRROR_HORIZONTAL	0
+#define MIRROR_VERTICAL		1
+#define MIRROR_FOUR_SCREEN	2
+
+
+static int load_ines2(struct nes_state *state, const char *path) {
+	FILE *f = fopen(path, "rb");
+	if(!f) {
+		return -1;
+	}
+
+	uint8_t header[INES_HEADER_SIZE];
+	fread(header, 1, INES_HEADER_SIZE, f);
+
+	uint8_t prg_lsb = header[INES_PRG_SIZE_LSB];
+	uint8_t chr_lsb = header[INES_CHR_SIZE_LSB];
+	uint8_t prg_msb = header[INES_PRG_CHR_MSB] & 0x0f;
+	uint8_t chr_msb = (header[INES_PRG_CHR_MSB] & 0xf0) >> 4;
+
+	uint32_t prg_size = (prg_msb << 8 | prg_lsb) * PRG_ROM_UNIT;
+	uint32_t chr_size = (chr_msb << 8 | chr_lsb) * CHR_ROM_UNIT;
+
+	// NES 2.0 exponential format (only if lower byte is 0x0f)
+	if(prg_lsb == 0x0f) {
+		prg_size = 1 << header[INES_PRG_EXP];
+	}
+	if(chr_lsb == 0x0f) {
+		chr_size = 1 << header[INES_CHR_EXP];
+	}
+
+	// Extract mapper
+	uint8_t mapper_low  = (header[INES_FLAGS6] >> 4);
+	uint8_t mapper_high = (header[INES_FLAGS7] & 0xf0);
+	uint8_t mapper_ext  = (header[INES_PRG_CHR_MSB] & 0x0f) << 8;
+	state->ines.mapper = mapper_low | mapper_high | mapper_ext;
+
+	// Extract mirroring
+	if(header[INES_FLAGS6] & FLAG6_FOUR_SCREEN) {
+		state->ines.mirroring = MIRROR_FOUR_SCREEN;
+	} else if(header[INES_FLAGS6] & FLAG6_VERTICAL_MIRROR) {
+		state->ines.mirroring = MIRROR_VERTICAL;
+	} else {
+		state->ines.mirroring = MIRROR_HORIZONTAL;
+	}
+
+	state->ines.prg_size = prg_size;
+	state->ines.chr_size = chr_size;
+
+	// Skip trainer if present
+	if(header[INES_FLAGS6] & FLAG6_TRAINER) {
+		fseek(f, TRAINER_SIZE, SEEK_CUR);
+	}
+
+	// Read PRG
+	fread(state->rom, 1, prg_size, f);
+
+	// Read CHR if present
+	if(chr_size > 0) {
+		fread(state->chrrom, 1, chr_size, f);
+	}
+
+	fclose(f);
+	return 0;
+}
+
+