{
char c[] = "0123456789abcdefghijklmnopqrstuvwxyz";
int i = 0;
while (n-i) {
unsigned long d = (unsigned long)pow(radix, n-i-1);
buf[i++] = c[val/d];
val = val%d;
}
buf[i] = '\0';
return buf;
}
int crc16op(char* msg, int n)
{
int i,j,crc=0; // crc-16 (0x8005 poly, flip in and out, 2 zero bytes in tail) of msg[0..n-1]
for(i=0;i!=n+2;i++){
if(i
for(j=0;j!=8;j++)
crc = crc&1 ? (crc>>1) ^ 0xa001 : crc>>1;
}
// replace, swap and store crc in msg[32..48]
crc = crc&0xff00 ? ( crc&0x00ff ? crc : 0x001b|(crc&0xff00) ) : 0x2b00|(crc&0x00ff);
crc = ((crc&0x00ff)<<8 amp="amp" crc="crc" xff00="xff00">>8);
return crc;
}
int main(int argc, const char* argv[]){
if(argc != 2){
printf("usage: opera [callsign]\n");
return 0;
}
const char* call = argv[1];
char msg[239];
int i,j;
char c[]=" "; //align last prefix digit at c[2] and fill gaps with blanks
int aligned = isdigit(call[2]);
strncpy(aligned ? c : &c[1], call, aligned ? 6 : 5);
strupr(c);
unsigned long n1=(c[0]>='0'&&c[0]<='9'?c[0]-'0'+27:c[0]==' '?0:c[0]-'A'+1); // packing call e.g. " K1JT ", "AA1AA " into n1
n1=36*n1+(c[1]>='0'&&c[1]<='9'?c[1]-'0'+26:c[1]-'A');
n1=10*n1+c[2]-'0';
n1=27*n1+(c[3]==' '?0:c[3]-'A'+1);
n1=27*n1+(c[4]==' '?0:c[4]-'A'+1);
n1=27*n1+(c[5]==' '?0:c[5]-'A'+1);
itoa(n1, 28, &msg[4], 2); //msg[4..32] = binary representation n1 in ASCII
itoa(crc16op(&msg[4], 28), 16, &msg[32], 2); //store bin-crc of msg[4..31] in msg[32..47]
itoa(crc16op(&msg[4], 28+16) & 0x07, 3, &msg[48], 2); //store bin-crc of msg[4..47] in msg[48..51]
msg[0]=msg[1]=msg[2]=msg[3]='0'; //unused bits msg[0-3]
const char* prn_vec = "111000010101011111100110110100000001100100010101011";
for(i=0; i!=51; i++) //scramble
msg[i] = ((msg[i]-'0') ^ (prn_vec[i]-'0')) +'0';
const char* wh[] = {"0000000", "1010101", "0110011", "1100110", "0001111", "1011010", "0111100", "1101001"};
for(i=(51/3)-1; i>=0; i--){ // Walsh-Hadamard encoding to msg[0..118]
char b = (msg[i*3+0]-'0')*4+(msg[i*3+1]-'0')*2+(msg[i*3+2]-'0')*1;
for(j=0; j!=7;j++)
msg[i*7+j] = wh[b][j];
}
for(i=0; i!=7; i++) // interleave 7x17 to msg[121..240]
for(j=0; j!=17; j++)
msg[121+j+17*i] = msg[i+7*j];
for(i=0; i!=119; i++){ // Manchester encoding to msg[2..120]
msg[2*i+1+2] = msg[121+i];
msg[2*i+0+2] = (msg[2*i+1+2] == '0') + '0';
}
msg[0] = msg[1] ='1'; // head
msg[239] = '\0'; // tail
printf("message=%s symbols=%s\n", c, msg);
}
