- Added support for reading, and writing outside the

  emulator's memory.

  All reads outside of the emulator's memory give back
  $/0xFF bytes, while all writes outside of the
  emulator's memory are ignored.

- Implemented malloc(), and free() in the SuB Suite.

  In order to do this, I had to add support for a heap,
  which I did by reserving the first 3 banks of the
  address space (the first 192K), and by adding a
  routine that finds the end of the RAM.

  In this case, I set the starting address for the
  routine at bank 3 (bank 4 with one indexing), but,
  the routine's starting address isn't hardcoded, and
  thus, any starting address can be passed as an
  argument.

  The routine uses the fact that we can now read/write
  outside the emulator's memory, and also uses the
  fact that writing outside the emulator's memory will
  be ignored, and that reading outside the emulator's
  memory will always read $/0xFF bytes, and uses that
  to signal that it's reached the end of the RAM.

- Added a test program for getting the size of RAM
  starting at address $/0x20000.

1 files changed, 47 insertions, 41 deletions

diff --git a/sux.h b/sux.h
index 8dbc064..509a6bc 100644
--- a/sux.h
+++ b/sux.h
@@ -77,56 +77,62 @@ static void *memcopy(void *restrict dst, const void *restrict src, unsigned int
 
 
 static inline uint64_t read_value(struct sux *cpu, uint64_t reg, uint64_t address, uint8_t size, uint8_t inc_clk, uint8_t check_io) {
-	#if (IO || debug) && !branch
-	#if keypoll
-	pthread_mutex_lock(&mutex);
-	#endif
-	if (check_io) {
-		io(address, 1);
-	}
-	#if keypoll
-	pthread_mutex_unlock(&mutex);
-	#endif
-	#endif
 	#if getclk
 	cpu->clk += inc_clk;
 	#endif
 	size = (size > 7) ? 7 : size;
-	#if 1
-	if (size < 7) {
-		uint64_t mask = (-(uint64_t)1 >> ((7 - size) * 8));
-		return (reg & ~mask) | (*(uint64_t *)(addr+address) & mask);
+	uint64_t mask = (-(uint64_t)1 >> ((7 - size) * 8));
+	if (address < mem_size) {
+		#if (IO || debug) && !branch
+		#if keypoll
+		pthread_mutex_lock(&mutex);
+		#endif
+		if (check_io) {
+			io(address, 1);
+		}
+		#if keypoll
+		pthread_mutex_unlock(&mutex);
+		#endif
+		#endif
+		#if 1
+		if (size < 7) {
+			return (reg & ~mask) | (*(uint64_t *)(addr+address) & mask);
+		} else {
+			return *(uint64_t *)(addr+address);
+		}
+		#else
+		return *(uint64_t *)memcopy(&reg, addr+address, size+1);
+		#endif
 	} else {
-		return *(uint64_t *)(addr+address);
+		return (size < 7) ? (reg & ~mask) | (mask) : mask;
 	}
-	#else
-	return *(uint64_t *)memcopy(&reg, addr+address, size+1);
-	#endif
 }
 
 static inline void write_value(struct sux *cpu, uint64_t value, uint64_t address, uint8_t size, uint8_t inc_clk, uint8_t check_io) {
-	size = (size > 7) ? 7 : size;
-	#if 1
-	if (size < 7) {
-		uint64_t mask = (-(uint64_t)1 >> ((7 - size) * 8));
-		*(uint64_t *)(addr+address) = (*(uint64_t *)(addr+address) & ~mask) | (value & mask);
-	} else {
-		*(uint64_t *)(addr+address) = value;
+	if (address < mem_size) {
+		size = (size > 7) ? 7 : size;
+		#if 1
+		if (size < 7) {
+			uint64_t mask = (-(uint64_t)1 >> ((7 - size) * 8));
+			*(uint64_t *)(addr+address) = (*(uint64_t *)(addr+address) & ~mask) | (value & mask);
+		} else {
+			*(uint64_t *)(addr+address) = value;
+		}
+		#else
+		memcopy(addr+address, &value, size+1);
+		#endif
+		#if (IO || debug) && !branch
+		#if keypoll
+		pthread_mutex_lock(&mutex);
+		#endif
+		if (check_io) {
+			io(address, 0);
+		}
+		#if keypoll
+		pthread_mutex_unlock(&mutex);
+		#endif
+		#endif
 	}
-	#else
-	memcopy(addr+address, &value, size+1);
-	#endif
-	#if (IO || debug) && !branch
-	#if keypoll
-	pthread_mutex_lock(&mutex);
-	#endif
-	if (check_io) {
-		io(address, 0);
-	}
-	#if keypoll
-	pthread_mutex_unlock(&mutex);
-	#endif
-	#endif
 	#if getclk
 	cpu->clk += inc_clk;
 	#endif
@@ -276,7 +282,7 @@ static inline uint64_t sbc(struct sux *cpu, uint64_t reg, uint64_t value, uint8_
 	setflag(sum == 0, Z);
 	setflag(sum >> 63, N);
 	setflag(((reg^value) >> 63) && ((reg^sum) >> 63), V);
-	setflag((sum > value), C);
+	setflag((sum < value), C);
 	return sum;
 }