beetle-pce-fast-libretro/mednafen/include/blip/Blip_Buffer.h

// Band-limited sound synthesis buffer
// Various changes and hacks for use in Mednafen.

// Blip_Buffer 0.4.1
#ifndef BLIP_BUFFER_H
#define BLIP_BUFFER_H

#include <limits.h>
#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif


// Internal
typedef int32_t blip_long;
typedef uint32_t blip_ulong;
typedef int64_t blip_s64;
typedef uint64_t blip_u64;

// Time unit at source clock rate
typedef blip_long blip_time_t;

// Output samples are 16-bit signed, with a range of -32768 to 32767
typedef short blip_sample_t;
enum { blip_sample_max = 32767 };

typedef const char* blargg_err_t;
typedef blip_u64 blip_resampled_time_t;
typedef blip_resampled_time_t resampled_time_t;
typedef blip_time_t blip_buf_t_;

typedef struct
{
   blip_u64 factor;
   blip_resampled_time_t offset;
   blip_buf_t_* buffer;
   blip_long buffer_size;
   blip_long reader_accum;
   int bass_shift;
   long sample_rate;
   long clock_rate;
   int bass_freq;
   int length;
   int modified;
} Blip_Buffer;

void Blip_Buffer_init(Blip_Buffer* bbuf);
void Blip_Buffer_deinit(Blip_Buffer* bbuf);

// Set output sample rate and buffer length in milliseconds (1/1000 sec, defaults
// to 1/4 second), then clear buffer. Returns NULL on success, otherwise if there
// isn't enough memory, returns error without affecting current buffer setup.
blargg_err_t Blip_Buffer_set_sample_rate(Blip_Buffer* bbuf,
      long samples_per_sec, int msec_length /*= 1000 / 4*/);

// End current time frame of specified duration and make its samples available
// (along with any still-unread samples) for reading with read_samples(). Begins
// a new time frame at the end of the current frame.
void Blip_Buffer_end_frame(Blip_Buffer* bbuf, blip_time_t time);

// Read at most 'max_samples' out of buffer into 'dest', removing them from from
// the buffer. Returns number of samples actually read and removed. If stereo is
// true, increments 'dest' one extra time after writing each sample, to allow
// easy interleving of two channels into a stereo output buffer.
long Blip_Buffer_read_samples(Blip_Buffer* bbuf, blip_sample_t* dest,
                              long max_samples);

// Additional optional features

// Set frequency high-pass filter frequency, where higher values reduce bass more
void Blip_Buffer_bass_freq(Blip_Buffer* bbuf, int frequency);

// Remove all available samples and clear buffer to silence. If 'entire_buffer' is
// false, just clears out any samples waiting rather than the entire buffer.
void Blip_Buffer_clear(Blip_Buffer* bbuf, int entire_buffer /*= 1*/);

// Number of samples available for reading with read_samples()
static INLINE long Blip_Buffer_samples_avail(Blip_Buffer* bbuf);

// Remove 'count' samples from those waiting to be read
void Blip_Buffer_remove_samples(Blip_Buffer* bbuf, long count);

// Experimental features

// Number of raw samples that can be mixed within frame of specified duration.
long Blip_Buffer_count_samples(Blip_Buffer* bbuf, blip_time_t duration);

// Mix 'count' samples from 'buf' into buffer.
void Blip_Buffer_mix_samples(Blip_Buffer* bbuf, blip_sample_t const* buf,
                             long count);

void Blip_Buffer_remove_silence(Blip_Buffer* bbuf, long count);

static INLINE blip_resampled_time_t Blip_Buffer_resampled_time(
   Blip_Buffer* bbuf, blip_time_t t)
{
   return t * bbuf->factor + bbuf->offset;
}
blip_resampled_time_t Blip_Buffer_clock_rate_factor(Blip_Buffer* bbuf,
      long clock_rate);


#define BLIP_BUFFER_ACCURACY 32
#define BLIP_PHASE_BITS 8

// Number of bits in resample ratio fraction. Higher values give a more accurate ratio
// but reduce maximum buffer size.
//#ifndef BLIP_BUFFER_ACCURACY
// #define BLIP_BUFFER_ACCURACY 16
//#endif

// Number bits in phase offset. Fewer than 6 bits (64 phase offsets) results in
// noticeable broadband noise when synthesizing high frequency square waves.
// Affects size of Blip_Synth objects since they store the waveform directly.
//#ifndef BLIP_PHASE_BITS
// #if BLIP_BUFFER_FAST
//    #define BLIP_PHASE_BITS 8
// #else
//    #define BLIP_PHASE_BITS 6
// #endif
//#endif

// Internal
#define blip_widest_impulse_  16
#define blip_buffer_extra_    (blip_widest_impulse_ + 2)
#define blip_res              (1 << BLIP_PHASE_BITS)
#define blip_sample_bits      30

// Range specifies the greatest expected change in amplitude. Calculate it
// by finding the difference between the maximum and minimum expected
// amplitudes (max - min).


typedef struct
{
   int delta_factor;
} Blip_Synth;

static INLINE void Blip_Synth_set_volume(Blip_Synth* synth, double v, int range)
{
   synth->delta_factor = ((v * (1.0 / (range < 0 ? -range : range))) *
                              (1L << blip_sample_bits) + 0.5);
}
// Works directly in terms of fractional output samples. Contact author for more info.
static INLINE void Blip_Synth_offset_resampled(Blip_Synth* synth, blip_resampled_time_t,
                                 int delta, Blip_Buffer*);

// Add an amplitude transition of specified delta, optionally into specified buffer
// rather than the one set with output(). Delta can be positive or negative.
// The actual change in amplitude is delta * (volume / range)

static INLINE void Blip_Synth_offset(Blip_Synth* synth, blip_time_t t, int delta,
                       Blip_Buffer* buf)
{
   Blip_Synth_offset_resampled(synth, t * buf->factor + buf->offset, delta, buf);
}

// Optimized reading from Blip_Buffer, for use in custom sample output

// Begin reading from buffer. Name should be unique to the current block.
#define BLIP_READER_BEGIN( name, blip_buffer ) \
   const blip_buf_t_* name##_reader_buf = (blip_buffer).buffer;\
   blip_long name##_reader_accum = (blip_buffer).reader_accum

// Get value to pass to BLIP_READER_NEXT()
#define BLIP_READER_BASS( blip_buffer ) ((blip_buffer).bass_shift)

// Current sample
#define BLIP_READER_READ( name )        (name##_reader_accum >> (blip_sample_bits - 16))

// Current raw sample in full internal resolution
#define BLIP_READER_READ_RAW( name )    (name##_reader_accum)

// Advance to next sample
#define BLIP_READER_NEXT( name, bass ) \
   (void) (name##_reader_accum += *name##_reader_buf++ - (name##_reader_accum >> (bass)))

// End reading samples from buffer. The number of samples read must now be removed
// using Blip_Buffer_remove_samples().
#define BLIP_READER_END( name, blip_buffer ) \
   (void) ((blip_buffer).reader_accum = name##_reader_accum)

// End of public interface


static INLINE void Blip_Synth_offset_resampled(
   Blip_Synth* synth,
   blip_resampled_time_t time,
   int delta, Blip_Buffer* blip_buf)
{
   int phase;
   blip_long* buf, left, right;

   delta *= synth->delta_factor;
   buf = blip_buf->buffer + (time >>
                                        BLIP_BUFFER_ACCURACY);
   phase = (int)(time >> (BLIP_BUFFER_ACCURACY - BLIP_PHASE_BITS) &
                     (blip_res - 1));

   left = buf [0] + delta;

   // Kind of crappy, but doing shift after multiply results in overflow.
   // Alternate way of delaying multiply by delta_factor results in worse
   // sub-sample resolution.
   right = (delta >> BLIP_PHASE_BITS) * phase;
   left  -= right;
   right += buf [1];

   buf [0] = left;
   buf [1] = right;
}

static INLINE long Blip_Buffer_samples_avail(Blip_Buffer* bbuf)
{
   return (long)(bbuf->offset >> BLIP_BUFFER_ACCURACY);
}

static INLINE void Blip_Buffer_set_clock_rate(Blip_Buffer* bbuf, long cps)
{
   bbuf->factor = Blip_Buffer_clock_rate_factor(bbuf, bbuf->clock_rate = cps);
}

#ifdef __cplusplus
}
#endif

#endif