#include "utils.h"

unsigned long seed = 0;

// returns values between 0 and 0x7FFF

// NB rngN depends on this output range, so if we change the

// behaviour rngN will need updating

long rng(void)

{

unsigned long m = 2147483648;

long a = 214013;

long c = 2531011;

seed = (a * seed + c) % m;

return seed >> 16;

}

void rngSeed(long newSeed)

{

seed = newSeed;

}

// returns 0 <= x < max where max <= 256

// (actual upper limit is higher, but there is one and I haven't

// thought carefully about what it is)

unsigned int rngN(unsigned int max)

{

unsigned long x = rng();

unsigned int result = (x * max) / RNG_MAX;

return result;

}

// 0..255 returned

long rng8Bit(void)

{

return rng() & 0b11111111;

}

// 0..31 returned

long rng5Bit(void)

{

return rng() & 0b11111;

}

// 0..255 returned

long rng0to2(void)

{

int randomNumber = rng() & 0b11;

while(randomNumber == 3) {

randomNumber = rng() & 0b11;

}

return randomNumber;

}