C CODE

The stars are encoded as unsigned integers (32 bits in this case).

The first (left-most, most-signicant) 9 bits are to hold an azimuth angle, ranging from 0 to 359 (inclusive). The next 8 bits hold an elevation angle, -90 to 90 (inclusive), in twos complement form, if negative. And that leaves the last 15 bits to hold a brightness from 0 to 2^15 - 1 (32767) (inclusive).

// goal: prints a binary representation of an (unsigned) int

// param x: variable to print the value of

void showbits(unsigned int x) {

for (int i = (8 * sizeof(unsigned int)) - 1; i >= 0; i--) {

putchar(x & (1u << i) ? '1' : '0');

}

printf(" ");

}

// goal: packs an azimuth, elevation, and brightness into a "star"

// param azimuth: desired value of the star's azimuth

// legal range: 0 to 359 (inclusive)

// param elevation: desired value of the star's elevation

// legal range: -90 to 90 (inclusive)

// param brightness: desired value of the star's brightness

// legal range: 0 to 2^15 - 1 (32767) (inclusive)

// psuedo-return *star: variable to pack values into

// 9 most significant bits hold the azimuth

// 8 middle bits hold the elevation (in two's complement)

// 15 least significant bits hold the brightness

// return: error code, -1 if any field outside valid range, 0 otherwise

// (if return -1, *star may take any value, no guarantees)

//

// TODO: Complete the function

int pack(unsigned int* star, int azimuth, int elevation, int brightness)

{

if ((azimuth < 0 && azimuth > 359) || (elevation < -90 && elevation > 90) || (brightness < 0 && brightness > 32767))

{

return -1;

}

else

{

int azi = azimuth << 24;

int ela = 9 >> (~(elevation) + 1) << 15;

int bri = brightness;

int result = azi | ela | bri;

*star = &result;

return 0;

}

}

I need help with this packing

i have tried to use my bitwis logic in my main:

int main()

{

//working on my bits logic here

unsigned int* p_red_Star;

int elevation = 40;//101000 => 1s(010111)(using tiddle) => 2s (011000)

printf("Elevation bits: ");

showbits(elevation << 15);

int azimuth = 200;//11001000

printf("Azimuth bits: ");

showbits(azimuth << 24);

int brightness = 15000;//11101010011000

printf("brightness bits: ");

showbits(brightness);

int ela_2s = ~(elevation) + 1;//11111111111111111111111111-011000

int shift = ela_2s >> 8;// its all 1s

int s_2 = ~(shift);// it will turn into a bunch of zeros

s_2 = s_2 << 8;

//trying to get this: 0000000000000000000000000-011000

//instead i got this: all of bunch of zeros

printf("2s elavation: ");

showbits(s_2); }