trs80m3: Added support for high-speed CAS files.

src/lib/formats/trs_cas.cpp

@@ -15,7 +15,7 @@ Support for TRS80 .cas cassette images
 #define SMPHI   32767
 
 
-static int cas_size; // FIXME: global variable prevents multiple instances
+static int cas_size = 0; // FIXME: global variable prevents multiple instances
 
 
 /*******************************************************************
@@ -41,10 +41,7 @@ static inline int trs80l2_cas_cycle(int16_t *buffer, int sample_pos, bool bit)
 static int trs80l2_handle_cas(int16_t *buffer, const uint8_t *casdata)
 {
 	int data_pos = 0, sample_count = 0;
-	bool a5sw = false;
+	bool sw = false;
-
-	data_pos = 0;
-	sample_count = 0;
 
 	while( data_pos < cas_size )
 	{
@@ -61,9 +58,9 @@ static int trs80l2_handle_cas(int16_t *buffer, const uint8_t *casdata)
 			data <<= 1;
 		}
 
-		if (!a5sw && (casdata[data_pos] == 0xA5))
+		if (!sw && (casdata[data_pos] == 0xA5))
 		{
-			a5sw = true;
+			sw = true;
 			// Need 1ms silence here while rom is busy
 			sample_count += trs80l2_cas_cycle( buffer, sample_count, false );
 		}
@@ -77,12 +74,91 @@ static int trs80l2_handle_cas(int16_t *buffer, const uint8_t *casdata)
 	return sample_count;
 }
 
+static inline int trs80m3_cas_cycle(int16_t *buffer, int sample_pos, bool bit)
+{
+	uint8_t i, counts = bit ? 8 : 16;
+
+	if ( buffer )
+	{
+		for (i = 0; i < counts; i++)
+			buffer[ sample_pos++ ] = SMPHI;
+		for (i = 0; i < counts; i++)
+			buffer[ sample_pos++ ] = SMPLO;
+	}
+	return counts*2;
+}
+
+
+static int trs80m3_handle_cas(int16_t *buffer, const uint8_t *casdata)
+{
+	int data_pos = 0, sample_count = 0;
+	uint8_t sw = 0, bitout = 0, byteout = 0;
+
+	// Make sure this is a trs80m3 tape
+	// Should have ~256 0x55 then one 0x7f
+	while ((cas_size > data_pos) && (casdata[data_pos] == 0x55))
+		data_pos++;
+	if (casdata[data_pos] != 0x7f)
+		return 0;
+
+	data_pos = 0;
+	while( data_pos < cas_size )
+	{
+		uint8_t data = casdata[data_pos];
+
+		for (uint8_t i = 0; i < 8; i++ )
+		{
+			sample_count += trs80m3_cas_cycle( buffer, sample_count, data >> 7 );
+
+			// This paragraph unscrambles and prints the SYSTEM name.
+			// If the first character is U, type SYSTEM, then the next 6 characters; otherwise use CLOAD.
+			if ((sw == 1) && buffer)
+			{
+				if (bitout)
+				{
+					byteout = (byteout << 1) | (data >> 7);
+					if (bitout == 8)
+					{
+						if (byteout == 0)
+							sw = 2;
+						printf("%c",byteout);
+						byteout = 0;
+						bitout = 0;
+					}
+					else
+						bitout++;
+				}
+				else bitout++;
+			}
+
+			data <<= 1;
+		}
+
+		if (!sw && (casdata[data_pos] == 0x7F))
+		{
+			sw = 1;
+			// This 1ms of silence isn't absolutely necessary, but the system writes it, so we may as emulate it.
+			sample_count += trs80l2_cas_cycle( buffer, sample_count, false );
+		}
+
+		data_pos++;
+	}
+
+	// Specification requires a short silence to indicate EOF
+	sample_count += trs80l2_cas_cycle( buffer, sample_count, false );
+	sample_count += trs80l2_cas_cycle( buffer, sample_count, false );
+	return sample_count;
+}
+
 
 /*******************************************************************
    Generate samples for the tape image
 ********************************************************************/
 static int trs80l2_cas_fill_wave(int16_t *buffer, int sample_count, uint8_t *bytes)
 {
+	if (cas_size && (bytes[0] == 0x55))
+		return trs80m3_handle_cas( buffer, bytes );
+	else
 		return trs80l2_handle_cas( buffer, bytes );
 }
 
@@ -94,6 +170,9 @@ static int trs80l2_cas_to_wav_size(const uint8_t *casdata, int caslen)
 {
 	cas_size = caslen;
 
+	if (cas_size && (casdata[0] == 0x55))
+		return trs80m3_handle_cas( nullptr, casdata );
+	else
 		return trs80l2_handle_cas( nullptr, casdata );
 }