tdlight/tdutils/td/utils/bits.h

//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2018
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once

#include "td/utils/common.h"
#include "td/utils/logging.h"

#if TD_MSVC
#include <intrin.h>
#endif

namespace td {

inline int32 count_leading_zeroes32(uint32 x);
inline int32 count_leading_zeroes64(uint64 x);
inline int32 count_trailing_zeroes32(uint32 x);
inline int32 count_trailing_zeroes64(uint64 x);
inline uint32 bswap32(uint32 x);
inline uint64 bswap64(uint64 x);
inline int32 count_bits32(uint32 x);
inline int32 count_bits64(uint64 x);

#if TD_MSVC
inline int32 count_leading_zeroes32(uint32 x) {
  unsigned long res = 0;
  if (_BitScanReverse(&res, x)) {
    return 31 - res;
  }
  return 32;
}

inline int32 count_leading_zeroes64(uint64 x) {
#if defined(_M_X64)
  unsigned long res = 0;
  if (_BitScanReverse64(&res, x)) {
    return 63 - res;
  }
  return 64;
#else
  if ((x >> 32) == 0) {
    return count_leading_zeroes32(static_cast<uint32>(x)) + 32;
  } else {
    return count_leading_zeroes32(static_cast<uint32>(x >> 32));
  }
#endif
}

inline int32 count_trailing_zeroes32(uint32 x) {
  unsigned long res = 0;
  if (_BitScanForward(&res, x)) {
    return res;
  }
  return 32;
}

inline int32 count_trailing_zeroes64(uint64 x) {
#if defined(_M_X64)
  unsigned long res = 0;
  if (_BitScanForward64(&res, x)) {
    return res;
  }
  return 64;
#else
  if (static_cast<uint32>(x) == 0) {
    return count_trailing_zeroes32(static_cast<uint32>(x >> 32)) + 32;
  } else {
    return count_trailing_zeroes32(static_cast<uint32>(x));
  }
#endif
}

inline uint32 bswap32(uint32 x) {
  return _byteswap_ulong(x);
}

inline uint64 bswap64(uint64 x) {
  return _byteswap_uint64(x);
}

inline int32 count_bits32(uint32 x) {
  return __popcnt(x);
}

inline int32 count_bits64(uint64 x) {
#if defined(_M_X64)
  return __popcnt64(x);
#else
  return count_bits32(static_cast<uint32>(x >> 32)) + count_bits32(static_cast<uint32>(x));
#endif
}
#else
inline int32 count_leading_zeroes32(uint32 x) {
  if (x == 0) {
    return 32;
  }
  return __builtin_clz(x);
}

inline int32 count_leading_zeroes64(uint64 x) {
  if (x == 0) {
    return 64;
  }
  return __builtin_clzll(x);
}

inline int32 count_trailing_zeroes32(uint32 x) {
  if (x == 0) {
    return 32;
  }
  return __builtin_ctz(x);
}

inline int32 count_trailing_zeroes64(uint64 x) {
  if (x == 0) {
    return 64;
  }
  return __builtin_ctzll(x);
}

inline uint32 bswap32(uint32 x) {
  return __builtin_bswap32(x);
}

inline uint64 bswap64(uint64 x) {
  return __builtin_bswap64(x);
}

inline int32 count_bits32(uint32 x) {
  return __builtin_popcount(x);
}

inline int32 count_bits64(uint64 x) {
  return __builtin_popcountll(x);
}
#endif

//TODO: optimize
inline int32 count_leading_zeroes_non_zero32(uint32 x) {
  DCHECK(x != 0);
  return count_leading_zeroes32(x);
}
inline int32 count_leading_zeroes_non_zero64(uint64 x) {
  DCHECK(x != 0);
  return count_leading_zeroes64(x);
}
inline int32 count_trailing_zeroes_non_zero32(uint32 x) {
  DCHECK(x != 0);
  return count_trailing_zeroes32(x);
}
inline int32 count_trailing_zeroes_non_zero64(uint64 x) {
  DCHECK(x != 0);
  return count_trailing_zeroes64(x);
}

}  // namespace td