// Copyright 2018 Ulf Adams
//
// The contents of this file may be used under the terms of the Apache License,
// Version 2.0.
//
//    (See accompanying file LICENSE-Apache or copy at
//     http://www.apache.org/licenses/LICENSE-2.0)
//
// Alternatively, the contents of this file may be used under the terms of
// the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE-Boost or copy at
//     https://www.boost.org/LICENSE_1_0.txt)
//
// Unless required by applicable law or agreed to in writing, this software
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.

#include "ryu/common.h"

// Returns e == 0 ? 1 : [log_2(5^e)]; requires 0 <= e <= 3528.
int32_t __log2pow5(const int32_t e) {
  // This approximation works up to the point that the multiplication overflows at e = 3529.
  // If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater
  // than 2^9297.
  assert(e >= 0);
  assert(e <= 3528);
  return (int32_t) ((((uint32_t) e) * 1217359) >> 19);
}

// Returns e == 0 ? 1 : ceil(log_2(5^e)); requires 0 <= e <= 3528.
int32_t __ceil_log2pow5(const int32_t e) {
  return log2pow5(e) + 1;
}