// Copyright 2016 The RE2 Authors.  All Rights Reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#ifndef UTIL_MIX_H_

#define UTIL_MIX_H_

#include <stddef.h>

#include <limits>

namespace re2 {

// Silence "truncation of constant value" warning for kMul in 32-bit mode.

// Since this is a header file, push and then pop to limit the scope.

#ifdef _MSC_VER

#pragma warning(push)

#pragma warning(disable: 4309)

#endif

class HashMix {

 public:

  HashMix() : hash_(1) {}

  explicit HashMix(size_t val) : hash_(val + 83) {}

  void Mix(size_t val) {

    static const size_t kMul = static_cast<size_t>(0xdc3eb94af8ab4c93ULL);

    hash_ *= kMul;

    hash_ = ((hash_ << 19) |

             (hash_ >> (std::numeric_limits<size_t>::digits - 19))) + val;

  }

  size_t get() const { return hash_; }

 private:

  size_t hash_;

};

#ifdef _MSC_VER

#pragma warning(pop)

#endif

}  // namespace re2

#endif  // UTIL_MIX_H_