/* sound_write.c -- Write samples to a SoundStream. */

#include <stdio.h>
#include <math.h>
#include "sound.h"


short encode_sample( double sample ) {
  unsigned short y, msb, lsb;

  /* Samples in AIFF and WAVE files are 16-bit signed.
     (y is a short to let me "/ 256" to get the msb.)
     This way of encoding doubles means that 
         Writing ultra-quiet sounds produces non-silence in the file.
	 Write zeroes, read back, get a DC offset.
     but also
         Read and write are symmetrical.
	    Read -> write -> exact same integers.
	    Write -> read -> centers of ranges of mapped doubles.
	 Reading never produces absolute value > 1.0 (actually always <).
	 Writing a sine function produces full-scale symmetrical output.
  */
  if( sample >= 1.0 ) {
    y = 32767;
  }
  else if( sample < -1.0 )  {
    y = -32768;
  } else {
    /* Casting rounds towards zero, grr. */
    y = ( sample + 1.0 ) * 32768.0;
    y -= 32768;
  }
  return( y );
}


void sound_write_short( unsigned short y, SoundStream *pSS ) {
  unsigned short msb, lsb;

  msb = y / 256;
  lsb = y % 256;
  if( pSS->little_endian ) {
    putc( lsb, pSS->byte_stream );
    putc( msb, pSS->byte_stream );
  } else {
    putc( msb, pSS->byte_stream );
    putc( lsb, pSS->byte_stream );
  }
}


void write_sample( double sample, SoundStream *pSS ) {
  sound_write_short( encode_sample( sample ), pSS );
}


void write_LR_short( short left, short right, SoundStream *pSS ) {
  sound_write_short( left, pSS );
  sound_write_short( right, pSS );
}


void write_LR( double left, double right, SoundStream *pSS ) {
  write_sample( left, pSS );
  write_sample( right, pSS );
}