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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

/* M_PI is declared in math.h */
#define PI M_PI

typedef unsigned int	UI;
typedef unsigned long int	UL;
typedef unsigned short int	US;
typedef unsigned char	UC;
typedef signed int		SI;
typedef signed long int	SL;
typedef signed short int	SS;
typedef signed char	SC;

#define attr(a) __attribute__((a))

#define packed attr(packed)

/* WAV header, 44-byte total */
typedef struct{
UL riff	packed;
UL len	packed;
UL wave	packed;
UL fmt	packed;
UL flen	packed;
US one	packed;
US chan	packed;
UL hz	packed;
UL bpsec	packed;
US bpsmp	packed;
US bitpsmp	packed;
UL dat	packed;
UL dlen	packed;
}WAVHDR;

int savefile(const char*const s,const void*const m,const int ml){
FILE*f=fopen(s,"wb");
int ok=0;
if(f){
ok=fwrite(m,1,ml,f)==ml;
fclose(f);
}
return ok;
}

/* "converts" 4-char string to long int */
#define dw(a) (*(UL*)(a))

/* Makes 44-byte header for 8-bit WAV in memory
usage: wavhdr(pointer,sampleRate,dataLength) */

void wavhdr(void*m,UL hz,UL dlen){
WAVHDR*p=m;
p->riff=dw("RIFF");
p->len=dlen+44;
p->wave=dw("WAVE");
p->fmt=dw("fmt ");
p->flen=0x10;
p->one=1;
p->chan=1;
p->hz=hz;
p->bpsec=hz;
p->bpsmp=1;
p->bitpsmp=8;
p->dat=dw("data");
p->dlen=dlen;
}

/* returns 8-bit sample for a sine wave */
UC sinewave(UL rate,float freq,UC amp,UL z){
return sin(z*((PI*2/rate)*freq))*amp+128;
}

/* make arbitrary audio data here */
void makeaud(UC*p,const UL rate,UL z){
float freq=500;
UC amp=120;
while(z--){
*p++=sinewave(rate,freq,amp,z);
}
}

/* makes wav file */
void makewav(const UL rate,const UL dlen){
const UL mlen=dlen+44;
UC*const m=malloc(mlen);
if(m){
wavhdr(m,rate,dlen);
makeaud(m+44,rate,dlen);
savefile("out.wav",m,mlen);
}
}

int main(){
if(sizeof(WAVHDR)!=44)puts("bad struct");
makewav(22050,64000);
return 0;
}

source