#include <bits/stdc++.h>
#include <sys/mman.h>

// https://github.com/evanj/hugepagedemo

using namespace std;

int main()
{
  static const size_t FOUR_GIB_IN_BYTES   = UINT64_C(4) << 30;
  static const size_t HUGE_2MIB_ALIGNMENT = UINT64_C(2) << 20;
  static const size_t HUGE_2MIB_MASK      = HUGE_2MIB_ALIGNMENT - 1;
  static const size_t HUGE_1GIB_ALIGNMENT = UINT64_C(1) << 30;
  static const size_t HUGE_1GIB_MASK      = HUGE_1GIB_ALIGNMENT - 1;

  bitset<31> huge_2mib_alignment(HUGE_2MIB_ALIGNMENT);
  bitset<31> huge_2mib_mask(HUGE_2MIB_MASK);

  bitset<31> huge_1gib_alignment(HUGE_1GIB_ALIGNMENT);
  bitset<31> huge_1gib_mask(HUGE_1GIB_MASK);
  

  cout << "FOUR_GIB_IN_BYTES   : " << FOUR_GIB_IN_BYTES
       << " 2^32: " << (uint64_t) pow(2,32) << endl;
  cout << "HUGE_2MIB_ALIGNMENT : " << HUGE_2MIB_ALIGNMENT             << endl;
  cout << "HUGE_2MIB_ALIGNMENT : " << huge_2mib_alignment.to_string() << endl;
  cout << "HUGE_2MIB_MASK      : " << HUGE_2MIB_MASK                  << endl;
  cout << "HUGE_2MIB_MASK      : " << huge_2mib_mask.to_string()      << endl;    
  cout << "HUGE_1GIB_ALIGNMENT : " << HUGE_1GIB_ALIGNMENT             << endl;
  cout << "HUGE_1GIB_ALIGNMENT : " << huge_1gib_alignment.to_string() << endl;
  cout << "HUGE_1GIB_MASK      : " << HUGE_1GIB_MASK                  << endl;
  cout << "HUGE_1GIB_MASK      : " << huge_1gib_mask.to_string()      << endl;

  void *plain_malloc = malloc(FOUR_GIB_IN_BYTES);
  
  printf("malloc 4GiB = %p; 2MiB aligned? %d; 1GiB aligned? %d\n",
         plain_malloc,
         ((size_t)plain_malloc & HUGE_2MIB_MASK) == 0,
         ((size_t)plain_malloc & HUGE_1GIB_MASK) == 0);
  
  free(plain_malloc);

  void *aligned = aligned_alloc(HUGE_1GIB_ALIGNMENT, FOUR_GIB_IN_BYTES);
  
  printf("aligned_alloc 4GiB = %p; 2MiB aligned? %d; 1GiB aligned? %d\n",
         aligned,
         ((size_t)aligned & HUGE_2MIB_MASK) == 0,
         ((size_t)aligned & HUGE_1GIB_MASK) == 0);

  madvise(aligned, FOUR_GIB_IN_BYTES, MADV_WILLNEED);
  memset(aligned, 1, FOUR_GIB_IN_BYTES);
  
  // cout << "sleeping..." << endl;
  //this_thread::sleep_for(chrono::seconds(60));
  
  free(aligned);

  return 0;
}