GENERATEUR DE BITS ALÉATOIRES

//generation de bits aléatoires avec une carte son
//par philippe pasty 2007

#include <windows.h>
#include <stdio.h>
#include <mmsystem.h>
#include <math.h>
#include <stdlib.h>

#define BUFSIZE 2000
short int *buffer;
HWAVEIN wavein;
WAVEHDR headerIn;

int fini;

void CALLBACK AudioProcIn(
    HWAVE  hWave,	// handle of waveform device
    UINT  uMsg,	// sent message
    DWORD  dwInstance,	// instance data
    DWORD  dwParam1,	// application-defined parameter
    DWORD  dwParam2	// application-defined parameter
   )
{
 if(uMsg==WIM_DATA)
 {
  fini=1;
 }
}

//prépare l'enregistrement PCM
int init()
{
 MMRESULT err;
 WAVEFORMATEX pwfx;
 int resolution=2; //16 bits
 int fechant=44100;//frequence d'echantillonage

 pwfx.wFormatTag =WAVE_FORMAT_PCM;
 pwfx.nChannels =1;
 pwfx.nSamplesPerSec = fechant;
 pwfx.nAvgBytesPerSec = fechant*resolution;
 pwfx.nBlockAlign =resolution;
 pwfx.wBitsPerSample = resolution<<3;
 pwfx.cbSize = 0;

 err = waveInOpen(&wavein,0,&pwfx,(DWORD)AudioProcIn,0,CALLBACK_FUNCTION);
 if (err==MMSYSERR_NOERROR)
  {
   headerIn.lpData =(LPSTR) buffer;
   headerIn.dwBytesRecorded = 0;
   headerIn.dwUser = 0;
   headerIn.dwFlags = 0;
   headerIn.dwLoops =1;
   headerIn.dwBufferLength = BUFSIZE*resolution;
   waveInPrepareHeader(wavein,&headerIn,sizeof(headerIn));

   waveInStart(wavein);
   return 1;
  }
  return 0;
}

//renvoie 0 ou 1 avec une probabilité 1/2
int aleatoire()
{
 static int pos=BUFSIZE-1;
 int dif;

 do{
  pos++;
  if(pos==BUFSIZE)
  {
   fini=0;
   waveInAddBuffer(wavein,&headerIn,sizeof(headerIn));
   while(!fini);
   pos=1;
  }
  dif= buffer[pos] - buffer[pos-1];
  if(dif<0) return 1;
  if(dif>0) return 0;
 }while(1);
}

int main()
{
  int n,s=0,bit;
  buffer =(short int*) malloc(BUFSIZE*2);

  if(!init()){printf("erreur sur la carte son\n"); return 0;}

  for (n=0;n<10000;n++)
  {if (!(n%50)) printf("\n%4d ",n);
   bit=aleatoire();s+=bit;
   printf("%d",bit);
  }
  printf("\nnombre de 1: %d\n",s);
  waveInUnprepareHeader(wavein,&headerIn,sizeof(headerIn));
  waveInClose(wavein);

  return 1;
}