#include <stdint.h>
#include "randombytes.h"

static uint32_t seed[32] = { 3,1,4,1,5,9,2,6,5,3,5,8,9,7,9,3,2,3,8,4,6,2,6,4,3,3,8,3,2,7,9,5 } ;
static uint32_t in[12];
static uint32_t out[8];
static int32_t outleft = 0;

#define ROTATE(x,b) (((x) << (b)) | ((x) >> (32 - (b))))
#define MUSH(i,b) x = t[i] += (((x ^ seed[i]) + sum) ^ ROTATE(x,b));

static void surf(void)
{
  uint32_t t[12]; uint32_t x; uint32_t sum = 0;
  int32_t r; int32_t i; int32_t loop;

  for (i = 0;i < 12;++i) t[i] = in[i] ^ seed[12 + i];
  for (i = 0;i < 8;++i) out[i] = seed[24 + i];
  x = t[11];
  for (loop = 0;loop < 2;++loop) {
    for (r = 0;r < 16;++r) {
      sum += 0x9e3779b9;
      MUSH(0,5) MUSH(1,7) MUSH(2,9) MUSH(3,13)
      MUSH(4,5) MUSH(5,7) MUSH(6,9) MUSH(7,13)
      MUSH(8,5) MUSH(9,7) MUSH(10,9) MUSH(11,13)
    }
    for (i = 0;i < 8;++i) out[i] ^= t[i + 4];
  }
}

void randombytes(uint8_t *x,uint64_t xlen)
{
  uint64_t bak = xlen;
  uint8_t *xbak = x;

  while (xlen > 0) {
    if (!outleft) {
      if (!++in[0]) if (!++in[1]) if (!++in[2]) ++in[3];
      surf();
      outleft = 8;
    }
    *x = out[--outleft];
    ++x;
    --xlen;
  }
}