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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2026
//
// 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"
#if TD_MSVC
#include <intrin.h>
#endif
#ifdef bswap32
#undef bswap32
#endif
#ifdef bswap64
#undef bswap64
#endif
namespace td {
int32 count_leading_zeroes32(uint32 x);
int32 count_leading_zeroes64(uint64 x);
int32 count_trailing_zeroes32(uint32 x);
int32 count_trailing_zeroes64(uint64 x);
uint32 bswap32(uint32 x);
uint64 bswap64(uint64 x);
int32 count_bits32(uint32 x);
int32 count_bits64(uint64 x);
inline uint32 bits_negate32(uint32 x) {
return ~x + 1;
}
inline uint64 bits_negate64(uint64 x) {
return ~x + 1;
}
inline uint32 lower_bit32(uint32 x) {
return x & bits_negate32(x);
}
inline uint64 lower_bit64(uint64 x) {
return x & bits_negate64(x);
}
inline uint64 host_to_big_endian64(uint64 x) {
// NB: works only for little-endian systems
return bswap64(x);
}
inline uint64 big_endian_to_host64(uint64 x) {
// NB: works only for little-endian systems
return bswap64(x);
}
//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);
}
//
// Platform specific implementation
//
#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) {
// Do not use __popcnt because it will fail on some platforms.
x -= (x >> 1) & 0x55555555;
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x += x >> 8;
return (x + (x >> 16)) & 0x3F;
}
inline int32 count_bits64(uint64 x) {
#if defined(_M_X64)
return static_cast<int32>(__popcnt64(x));
#else
return count_bits32(static_cast<uint32>(x >> 32)) + count_bits32(static_cast<uint32>(x));
#endif
}
#elif TD_INTEL
inline int32 count_leading_zeroes32(uint32 x) {
unsigned __int32 res = 0;
if (_BitScanReverse(&res, x)) {
return 31 - res;
}
return 32;
}
inline int32 count_leading_zeroes64(uint64 x) {
#if defined(_M_X64) || defined(__x86_64__)
unsigned __int32 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 __int32 res = 0;
if (_BitScanForward(&res, x)) {
return res;
}
return 32;
}
inline int32 count_trailing_zeroes64(uint64 x) {
#if defined(_M_X64) || defined(__x86_64__)
unsigned __int32 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 _bswap(static_cast<int>(x));
}
inline uint64 bswap64(uint64 x) {
return _bswap64(static_cast<__int64>(x));
}
inline int32 count_bits32(uint32 x) {
x -= (x >> 1) & 0x55555555;
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x += x >> 8;
return (x + (x >> 16)) & 0x3F;
}
inline int32 count_bits64(uint64 x) {
return count_bits32(static_cast<uint32>(x >> 32)) + count_bits32(static_cast<uint32>(x));
}
#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
struct BitsRange {
explicit BitsRange(uint64 bits = 0) : bits{bits}, pos{-1} {
}
BitsRange begin() const {
return *this;
}
BitsRange end() const {
return BitsRange{};
}
int32 operator*() const {
if (pos == -1) {
pos = count_trailing_zeroes64(bits);
}
return pos;
}
bool operator!=(const BitsRange &other) const {
return bits != other.bits;
}
BitsRange &operator++() {
auto i = **this;
if (i != 64) {
bits ^= 1ull << i;
}
pos = -1;
return *this;
}
private:
uint64 bits{0};
mutable int32 pos{-1};
};
} // namespace td
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