mame/src/lib/formats/vt_cas.cpp

// license:GPL-2.0+
// copyright-holders:Juergen Buchmueller
#include <assert.h>

#include "formats/vt_cas.h"

/*********************************************************************
    vtech 1/2 agnostic
*********************************************************************/

#define SILENCE 8000

static int generic_fill_wave(INT16 *buffer, int length, UINT8 *code, int bitsamples, int bytesamples, int lo, INT16 *(*fill_wave_byte)(INT16 *buffer, int byte))
{
	static int nullbyte;

	if( code == CODE_HEADER )
	{
		int i;

		if( length < SILENCE )
			return -1;
		for( i = 0; i < SILENCE; i++ )
			*buffer++ = 0;

		nullbyte = 0;

		return SILENCE;
	}

	if( code == CODE_TRAILER )
	{
		int i;

		/* silence at the end */
		for( i = 0; i < length; i++ )
			*buffer++ = 0;
		return length;
	}

	if( length < bytesamples )
		return -1;

	buffer = fill_wave_byte(buffer, *code);

	if( !nullbyte && *code == 0 )
	{
		int i;
		for( i = 0; i < 2*bitsamples; i++ )
			*buffer++ = lo;
		nullbyte = 1;
		return bytesamples + 2 * bitsamples;
	}

	return bytesamples;
}


/*********************************************************************
    vtech 1
*********************************************************************/

#define V1_LO   -32768
#define V1_HI   +32767

#define V1_BITSAMPLES   6
#define V1_BYTESAMPLES  8*V1_BITSAMPLES

static INT16 *vtech1_fill_wave_byte(INT16 *buffer, int byte)
{
	int i;

	for( i = 7; i >= 0; i-- )
	{
		*buffer++ = V1_HI;  /* initial cycle */
		*buffer++ = V1_LO;
		if( (byte >> i) & 1 )
		{
			*buffer++ = V1_HI; /* two more cycles */
			*buffer++ = V1_LO;
			*buffer++ = V1_HI;
			*buffer++ = V1_LO;
		}
		else
		{
			*buffer++ = V1_HI; /* one slow cycle */
			*buffer++ = V1_HI;
			*buffer++ = V1_LO;
			*buffer++ = V1_LO;
		}
	}
	return buffer;
}

static int vtech1_cassette_fill_wave(INT16 *buffer, int length, UINT8 *code)
{
	return generic_fill_wave(buffer, length, code, V1_BITSAMPLES, V1_BYTESAMPLES, V1_LO, vtech1_fill_wave_byte);
}

static const struct CassetteLegacyWaveFiller vtech1_legacy_fill_wave =
{
	vtech1_cassette_fill_wave,  /* fill_wave */
	1,                          /* chunk_size */
	V1_BYTESAMPLES,             /* chunk_samples */
	nullptr,                       /* chunk_sample_calc */
	600*V1_BITSAMPLES,          /* sample_frequency */
	600*V1_BITSAMPLES,          /* header_samples */
	600*V1_BITSAMPLES           /* trailer_samples */
};

static casserr_t vtech1_cas_identify(cassette_image *cassette, struct CassetteOptions *opts)
{
	return cassette_legacy_identify(cassette, opts, &vtech1_legacy_fill_wave);
}

static casserr_t vtech1_cas_load(cassette_image *cassette)
{
	return cassette_legacy_construct(cassette, &vtech1_legacy_fill_wave);
}

static const struct CassetteFormat vtech1_cas_format =
{
	"cas",
	vtech1_cas_identify,
	vtech1_cas_load,
	nullptr
};

CASSETTE_FORMATLIST_START(vtech1_cassette_formats)
	CASSETTE_FORMAT(vtech1_cas_format)
CASSETTE_FORMATLIST_END

/*********************************************************************
    vtech 2
*********************************************************************/

#define VT2_LO  -20000
#define VT2_HI  +20000

#define VT2_BITSAMPLES  18
#define VT2_BYTESAMPLES 8*VT2_BITSAMPLES

static const INT16 vtech2_bit0[VT2_BITSAMPLES] =
{
	/* short cycle, long cycles */
	VT2_HI,VT2_HI,VT2_HI,VT2_LO,VT2_LO,VT2_LO,
	VT2_HI,VT2_HI,VT2_HI,VT2_HI,VT2_HI,VT2_HI,
	VT2_LO,VT2_LO,VT2_LO,VT2_LO,VT2_LO,VT2_LO
};

static const INT16 vtech2_bit1[VT2_BITSAMPLES] =
{
	/* three short cycle */
	VT2_HI,VT2_HI,VT2_HI,VT2_LO,VT2_LO,VT2_LO,
	VT2_HI,VT2_HI,VT2_HI,VT2_LO,VT2_LO,VT2_LO,
	VT2_HI,VT2_HI,VT2_HI,VT2_LO,VT2_LO,VT2_LO
};


static INT16 *vtech2_fill_wave_bit(INT16 *buffer, int bit)
{
	int i;
	if( bit )
	{
		for( i = 0; i < VT2_BITSAMPLES; i++ )
			*buffer++ = vtech2_bit1[i];
	}
	else
	{
		for( i = 0; i < VT2_BITSAMPLES; i++ )
			*buffer++ = vtech2_bit0[i];
	}
	return buffer;
}


static INT16 *vtech2_fill_wave_byte(INT16 *buffer, int byte)
{
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 7) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 6) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 5) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 4) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 3) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 2) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 1) & 1);
	buffer = vtech2_fill_wave_bit(buffer, (byte >> 0) & 1);
	return buffer;
}

static int vtech2_cassette_fill_wave(INT16 *buffer, int length, UINT8 *code)
{
	return generic_fill_wave(buffer, length, code, VT2_BITSAMPLES, VT2_BYTESAMPLES, VT2_LO, vtech2_fill_wave_byte);
}

static const struct CassetteLegacyWaveFiller vtech2_legacy_fill_wave =
{
	vtech2_cassette_fill_wave,  /* fill_wave */
	1,                          /* chunk_size */
	VT2_BYTESAMPLES,            /* chunk_samples */
	nullptr,                       /* chunk_sample_calc */
	600*VT2_BITSAMPLES,         /* sample_frequency */
	600*VT2_BITSAMPLES,         /* header_samples */
	600*VT2_BITSAMPLES          /* trailer_samples */
};

static casserr_t vtech2_cas_identify(cassette_image *cassette, struct CassetteOptions *opts)
{
	return cassette_legacy_identify(cassette, opts, &vtech2_legacy_fill_wave);
}

static casserr_t vtech2_cas_load(cassette_image *cassette)
{
	return cassette_legacy_construct(cassette, &vtech2_legacy_fill_wave);
}

static const struct CassetteFormat vtech2_cas_format =
{
	"cas",
	vtech2_cas_identify,
	vtech2_cas_load,
	nullptr
};

CASSETTE_FORMATLIST_START(vtech2_cassette_formats)
	CASSETTE_FORMAT(vtech2_cas_format)
CASSETTE_FORMATLIST_END