GBA: Ability to use an external source for the RTC

src/gba/gba-gpio.c

@@ -242,7 +242,14 @@ unsigned _rtcOutput(struct GBACartridgeGPIO* gpio) {
 }
 
 void _rtcUpdateClock(struct GBACartridgeGPIO* gpio) {
-	time_t t = time(0);
+	time_t t;
+	struct GBARTCSource* rtc = gpio->p->rtcSource;
+	if (rtc) {
+		rtc->sample(rtc);
+		t = rtc->unixTime(rtc);
+	} else {
+		t = time(0);
+	}
 	struct tm date;
 #ifdef _WIN32
 	date = *localtime(&t);

src/gba/gba-sensors.h

@@ -23,4 +23,10 @@ struct GBALuminanceSource {
 	uint8_t (*readLuminance)(struct GBALuminanceSource*);
 };
 
+struct GBARTCSource {
+	void (*sample)(struct GBARTCSource*);
+
+	time_t (*unixTime)(struct GBARTCSource*);
+};
+
 #endif

src/gba/gba.c

@@ -156,6 +156,8 @@ static void GBAInit(struct ARMCore* cpu, struct ARMComponent* component) {
 	gba->springIRQ = 0;
 	gba->keySource = 0;
 	gba->rotationSource = 0;
+	gba->luminanceSource = 0;
+	gba->rtcSource = 0;
 	gba->rumble = 0;
 	gba->rr = 0;
 

src/gba/gba.h

@@ -116,6 +116,7 @@ struct GBA {
 	uint32_t busyLoop;
 	struct GBARotationSource* rotationSource;
 	struct GBALuminanceSource* luminanceSource;
+	struct GBARTCSource* rtcSource;
 	struct GBARumble* rumble;
 
 	struct GBARRContext* rr;