www.pudn.com > lib.zip > sinegen.C

/* Modem for MIPS   AJF	  January 1995 
   Sine generator */ 
 
#include  
#include  
 
#include "private.h" 
#include "complex.h" 
#include "sinegen.h" 
#include "myaudio.h" 
 
#define SLENK	11 // ??? was 15 
#define SINELEN (1 << SLENK) 
#define TWO32	4.294967296e9	/* 2^32 */ 
#define TWOPI	(2.0 * M_PI) 
 
static struct Init_Sines 
  { Init_Sines(); 
  } 
init_sines; 
 
static float *sinetab; 
 
Init_Sines::Init_Sines() 
  { /* once-only initialization, done before main() is called */ 
    sinetab = new float[SINELEN]; 
    if (sinetab == NULL) 
      { fprintf(stderr, "No room! Init_Sines\r\n"); 
	exit(1); 
      } 
    for (int k = 0; k < SINELEN; k++) 
      { float th = TWOPI * (float) k / (float) SINELEN; 
	sinetab[k] = sin(th); 
      } 
  } 
 
sinegen::sinegen(float f) 
  { setfreq(f); 
    resetphase(); 
  } 
 
void sinegen::setfreq(float f) 
  { phinc = (int) (f * TWO32 / (float) SAMPLERATE); 
  } 
 
float sinegen::fnext() 
  { float x = sinetab[ptr >> (32-SLENK)];	/* keep top SLENK bits */ 
    ptr += phinc; 
    return x; 
  } 
 
complex sinegen::cnext() 
  { complex z = complex(sinetab[ptr >> (32-SLENK)], 
			sinetab[(ptr + (1 << 30)) >> (32-SLENK)]); 
    ptr += phinc; 
    return z; 
  }