upb/base/internal/log2.h

// Protocol Buffers - Google's data interchange format
// Copyright 2023 Google LLC.  All rights reserved.
// https://developers.google.com/protocol-buffers/
///
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

#ifndef UPB_BASE_INTERNAL_LOG2_H_
#define UPB_BASE_INTERNAL_LOG2_H_

// Must be last.
#include "upb/port/def.inc"

#ifdef __cplusplus
extern "C" {
#endif

UPB_INLINE int upb_Log2Ceiling(int x) {
  if (x <= 1) return 0;
#ifdef __GNUC__
  return 32 - __builtin_clz(x - 1);
#else
  int lg2 = 0;
  while ((1 << lg2) < x) lg2++;
  return lg2;
#endif
}

UPB_INLINE int upb_RoundUpToPowerOfTwo(int x) {
  return 1 << upb_Log2Ceiling(x);
}

#ifdef __cplusplus
} /* extern "C" */
#endif

#include "upb/port/undef.inc"

#endif /* UPB_BASE_INTERNAL_LOG2_H_ */