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#pragma once
#include "base/assert.hpp"
#include <cstdint>
#include <limits>
#include <type_traits>
namespace bits
{
// Count the number of 1 bits. Implementation: see Hacker's delight book.
inline uint32_t PopCount(uint32_t x) noexcept
{
x -= ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x += (x >> 8);
x += (x >> 16);
return x & 0x3F;
}
inline uint32_t PopCount(uint8_t x) noexcept
{
return PopCount(static_cast<uint32_t>(x));
}
// Count the number of 1 bits in array p, length n bits.
// There is a better implementation at hackersdelight.org
inline uint32_t PopCount(uint32_t const * p, uint32_t n)
{
uint32_t s = 0;
for (uint32_t i = 0; i < n; i += 31)
{
uint32_t lim = (n < i + 31 ? n : i + 31);
uint32_t s8 = 0;
uint32_t x = 0;
for (uint32_t j = i; j < lim; ++j)
{
x = p[j];
x -= ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
s8 += x;
}
x = (s8 & 0x00FF00FF) + ((s8 >> 8) & 0x00FF00FF);
x = (x & 0x0000ffff) + (x >> 16);
s += x;
}
return s;
}
static const int SELECT1_ERROR = -1;
template <typename T> unsigned int select1(T x, unsigned int i)
{
// TODO: Fast implementation of select1.
ASSERT(i > 0 && i <= sizeof(T) * 8, (i));
for (unsigned int j = 0; j < sizeof(T) * 8; x >>= 1, ++j)
if (x & 1)
if (--i == 0)
return j;
return static_cast<unsigned int>(SELECT1_ERROR);
}
inline uint32_t PopCount(uint64_t x) noexcept
{
x = x - ((x & 0xAAAAAAAAAAAAAAAA) >> 1);
x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
x = (x + (x >> 4)) & 0x0F0F0F0F0F0F0F0F;
x = (x * 0x0101010101010101) >> 56;
return static_cast<uint32_t>(x);
}
inline uint8_t CeilLog(uint64_t x) noexcept
{
#define CHECK_RSH(x, msb, offset) \
if (x >> offset) \
{ \
x >>= offset; \
msb += offset; \
}
uint8_t msb = 0;
CHECK_RSH(x, msb, 32);
CHECK_RSH(x, msb, 16);
CHECK_RSH(x, msb, 8);
CHECK_RSH(x, msb, 4);
CHECK_RSH(x, msb, 2);
CHECK_RSH(x, msb, 1);
#undef CHECK_RSH
return msb;
}
// Will be implemented when needed.
uint64_t PopCount(uint64_t const * p, uint64_t n);
template <typename T> T RoundLastBitsUpAndShiftRight(T x, T bits)
{
return (x & ((1 << bits) - 1)) ? (x >> bits) + 1 : (x >> bits);
}
template <typename T> struct LogBitSizeOfType;
template <> struct LogBitSizeOfType<uint8_t> { enum { value = 3 }; };
template <> struct LogBitSizeOfType<uint16_t> { enum { value = 4 }; };
template <> struct LogBitSizeOfType<uint32_t> { enum { value = 5 }; };
template <> struct LogBitSizeOfType<uint64_t> { enum { value = 6 }; };
template <typename T> T ROL(T x)
{
return (x << 1) | (x >> (sizeof(T) * 8 - 1));
}
template <typename T> inline typename std::make_unsigned<T>::type ZigZagEncode(T x)
{
static_assert(std::is_signed<T>::value, "Type should be signed");
return (x << 1) ^ (x >> (sizeof(x) * 8 - 1));
}
template <typename T> inline typename std::make_signed<T>::type ZigZagDecode(T x)
{
static_assert(std::is_unsigned<T>::value, "Type should be unsigned.");
return (x >> 1) ^ -static_cast<typename std::make_signed<T>::type>(x & 1);
}
inline uint32_t PerfectShuffle(uint32_t x)
{
x = ((x & 0x0000FF00) << 8) | ((x >> 8) & 0x0000FF00) | (x & 0xFF0000FF);
x = ((x & 0x00F000F0) << 4) | ((x >> 4) & 0x00F000F0) | (x & 0xF00FF00F);
x = ((x & 0x0C0C0C0C) << 2) | ((x >> 2) & 0x0C0C0C0C) | (x & 0xC3C3C3C3);
x = ((x & 0x22222222) << 1) | ((x >> 1) & 0x22222222) | (x & 0x99999999);
return x;
}
inline uint32_t PerfectUnshuffle(uint32_t x)
{
x = ((x & 0x22222222) << 1) | ((x >> 1) & 0x22222222) | (x & 0x99999999);
x = ((x & 0x0C0C0C0C) << 2) | ((x >> 2) & 0x0C0C0C0C) | (x & 0xC3C3C3C3);
x = ((x & 0x00F000F0) << 4) | ((x >> 4) & 0x00F000F0) | (x & 0xF00FF00F);
x = ((x & 0x0000FF00) << 8) | ((x >> 8) & 0x0000FF00) | (x & 0xFF0000FF);
return x;
}
inline uint64_t BitwiseMerge(uint32_t x, uint32_t y)
{
uint32_t const hi = PerfectShuffle((y & 0xFFFF0000) | (x >> 16));
uint32_t const lo = PerfectShuffle(((y & 0xFFFF) << 16 ) | (x & 0xFFFF));
return (static_cast<uint64_t>(hi) << 32) + lo;
}
inline void BitwiseSplit(uint64_t v, uint32_t & x, uint32_t & y)
{
uint32_t const hi = bits::PerfectUnshuffle(static_cast<uint32_t>(v >> 32));
uint32_t const lo = bits::PerfectUnshuffle(static_cast<uint32_t>(v & 0xFFFFFFFFULL));
x = ((hi & 0xFFFF) << 16) | (lo & 0xFFFF);
y = (hi & 0xFFFF0000) | (lo >> 16);
}
// Returns 1 if bit is set and 0 otherwise.
inline uint8_t GetBit(void const * p, uint32_t offset)
{
uint8_t const * pData = static_cast<uint8_t const *>(p);
return (pData[offset >> 3] >> (offset & 7)) & 1;
}
inline void SetBitTo0(void * p, uint32_t offset)
{
uint8_t * pData = static_cast<uint8_t *>(p);
pData[offset >> 3] &= ~(1 << (offset & 7));
}
inline void SetBitTo1(void * p, uint32_t offset)
{
uint8_t * pData = static_cast<uint8_t *>(p);
pData[offset >> 3] |= (1 << (offset & 7));
}
// Compute number of zero bits from the most significant bits side.
inline uint32_t NumHiZeroBits32(uint32_t n)
{
if (n == 0) return 32;
uint32_t result = 0;
while ((n & (uint32_t(1) << 31)) == 0) { ++result; n <<= 1; }
return result;
}
inline uint32_t NumHiZeroBits64(uint64_t n)
{
if (n == 0) return 64;
uint32_t result = 0;
while ((n & (uint64_t(1) << 63)) == 0) { ++result; n <<= 1; }
return result;
}
// Computes number of bits needed to store the number, it is not equal to number of ones.
// E.g. if we have a number (in bit representation) 00001000b then NumUsedBits is 4.
inline uint32_t NumUsedBits(uint64_t n)
{
uint32_t result = 0;
while (n != 0) { ++result; n >>= 1; }
return result;
}
inline uint64_t GetFullMask(uint8_t numBits)
{
ASSERT_LESS_OR_EQUAL(numBits, 64, ());
return numBits == 64 ? std::numeric_limits<uint64_t>::max()
: (static_cast<uint64_t>(1) << numBits) - 1;
}
} // namespace bits
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