code: func HashToBig(hash *chainhash.Hash) *big.Int {
  	// A Hash is in little-endian, but the big package wants the bytes in
  	// big-endian, so reverse them.
  	buf := *hash
  	blen := len(buf)
  	for i := 0; i < blen/2; i++ {
  		buf[i], buf[blen-1-i] = buf[blen-1-i], buf[i]
  	}
  
  	return new(big.Int).SetBytes(buf[:])
  }
docs: // HashToBig converts a chainhash.Hash into a big.Int that can be used to
  // perform math comparisons.