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https://github.com/holub/mame
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158 lines
2.8 KiB
C
158 lines
2.8 KiB
C
/* .APT tape images */
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#include "formats/apf_apt.h"
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#define WAVEENTRY_LOW -32768
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#define WAVEENTRY_HIGH 32767
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#define WAVEENTRY_NULL 0
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/* frequency of wave */
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#define APF_WAV_FREQUENCY 11050
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#define APF_APT_BIT_0_LENGTH ((int)(APF_WAV_FREQUENCY*0.0005))
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#define APF_APT_BIT_1_LENGTH ((int)(APF_WAV_FREQUENCY*0.001))
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struct apf_t
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{
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int cassette_length;
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};
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static apf_t apf;
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/* 500 microsecond of bit 0 and 1000 microsecond of bit 1 */
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static INT16 *apf_emit_level(INT16 *p, int count, INT16 wave_state)
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{
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int i;
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for (i=0; i<count; i++)
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{
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*(p++) = wave_state;
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}
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return p;
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}
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/* 4 periods at 1200Hz */
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static INT16* apf_output_bit(INT16 *p, UINT8 b)
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{
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if (b)
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{
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p = apf_emit_level(p, (APF_APT_BIT_1_LENGTH>>1), WAVEENTRY_HIGH);
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p = apf_emit_level(p, (APF_APT_BIT_1_LENGTH>>1), WAVEENTRY_LOW);
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}
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else
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{
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p = apf_emit_level(p, (APF_APT_BIT_0_LENGTH>>1), WAVEENTRY_HIGH);
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p = apf_emit_level(p, (APF_APT_BIT_0_LENGTH>>1), WAVEENTRY_LOW);
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}
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return p;
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}
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static int apf_get_bit_size_in_samples(UINT8 b)
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{
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if (b)
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{
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return APF_APT_BIT_1_LENGTH;
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}
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return APF_APT_BIT_0_LENGTH;
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}
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/*************************************************************************************/
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/* each bit in the data represents a "1" or "0" waveform */
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static int apf_cassette_calculate_size_in_samples(const UINT8 *bytes, int length)
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{
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unsigned i;
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int size;
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int b;
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UINT8 data;
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size = 0;
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apf.cassette_length = length;
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for (i=0; i<length; i++)
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{
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data = bytes[i];
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for (b=0; b<8; b++)
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{
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size += apf_get_bit_size_in_samples((data>>7) & 0x01);
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data = data<<1;
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}
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}
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return size;
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}
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/*************************************************************************************/
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static int apf_cassette_fill_wave(INT16 *buffer, int length, UINT8 *bytes)
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{
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int i;
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INT16 *p;
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UINT8 data;
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int b;
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p = buffer;
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for (i=0; i<apf.cassette_length; i++)
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{
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data = bytes[i];
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for (b=0; b<8; b++)
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{
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p = apf_output_bit(p,(data>>7) & 0x01);
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data = data<<1;
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}
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}
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return p - buffer;
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}
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static const struct CassetteLegacyWaveFiller apf_legacy_fill_wave =
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{
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apf_cassette_fill_wave, /* fill_wave */
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-1, /* chunk_size */
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0, /* chunk_samples */
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apf_cassette_calculate_size_in_samples, /* chunk_sample_calc */
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APF_WAV_FREQUENCY, /* sample_frequency */
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0, /* header_samples */
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0 /* trailer_samples */
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};
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static casserr_t apf_apt_identify(cassette_image *cassette, struct CassetteOptions *opts)
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{
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return cassette_legacy_identify(cassette, opts, &apf_legacy_fill_wave);
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}
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static casserr_t apf_apt_load(cassette_image *cassette)
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{
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return cassette_legacy_construct(cassette, &apf_legacy_fill_wave);
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}
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static const struct CassetteFormat apf_apt_format =
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{
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"apt",
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apf_apt_identify,
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apf_apt_load,
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NULL
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};
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CASSETTE_FORMATLIST_START(apf_cassette_formats)
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CASSETTE_FORMAT(apf_apt_format)
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CASSETTE_FORMATLIST_END
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