// Copyright 2023 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.

#include "re2/bitmap256.h"

#include <stdint.h>

#include "absl/log/absl_check.h"

namespace re2 {

int Bitmap256::FindNextSetBit(int c) const {

  ABSL_DCHECK_GE(c, 0);

  ABSL_DCHECK_LE(c, 255);

  // Check the word that contains the bit. Mask out any lower bits.

  int i = c / 64;

  uint64_t word = words_[i] & (~uint64_t{0} << (c % 64));

  if (word != 0)

    return (i * 64) + FindLSBSet(word);

  // Check any following words.

  i++;

  switch (i) {

    case 1:

      if (words_[1] != 0)

        return (1 * 64) + FindLSBSet(words_[1]);

      [[fallthrough]];

    case 2:

      if (words_[2] != 0)

        return (2 * 64) + FindLSBSet(words_[2]);

      [[fallthrough]];

    case 3:

      if (words_[3] != 0)

        return (3 * 64) + FindLSBSet(words_[3]);

      [[fallthrough]];

    default:

      return -1;

  }

}

}  // namespace re2