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fs: implement PooledBuffer

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This commit is contained in:
Michael Scire 2020-04-06 03:15:24 -07:00
parent 50a91b1d6e
commit 496be5ecd4
5 changed files with 521 additions and 6 deletions
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139
libraries/libvapours/include/vapours/util/util_bitutil.hpp
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@ -20,6 +20,16 @@
namespace ams::util {
namespace impl {
template<size_t N>
constexpr inline size_t Log2 = Log2<N / 2> + 1;
template<>
constexpr inline size_t Log2<1> = 0;
}
template <typename T>
class BitsOf {
private:
@ -73,4 +83,133 @@ namespace ams::util {
return (... | (T(1u) << args));
}
template<typename T>
constexpr ALWAYS_INLINE T ResetLeastSignificantOneBit(T x) {
return x & (x - 1);
}
template<typename T>
constexpr ALWAYS_INLINE T SetLeastSignificantZeroBit(T x) {
return x | (x + 1);
}
template<typename T>
constexpr ALWAYS_INLINE T LeastSignificantOneBit(T x) {
return x & ~(x - 1);
}
template<typename T>
constexpr ALWAYS_INLINE T LeastSignificantZeroBit(T x) {
return ~x & (x + 1);
}
template<typename T>
constexpr ALWAYS_INLINE T ResetTrailingOnes(T x) {
return x & (x + 1);
}
template<typename T>
constexpr ALWAYS_INLINE T SetTrailingZeros(T x) {
return x | (x - 1);
}
template<typename T>
constexpr ALWAYS_INLINE T MaskTrailingZeros(T x) {
return (~x) & (x - 1);
}
template<typename T>
constexpr ALWAYS_INLINE T MaskTrailingOnes(T x) {
return ~((~x) | (x + 1));
}
template<typename T>
constexpr ALWAYS_INLINE T MaskTrailingZerosAndLeastSignificantOneBit(T x) {
return x ^ (x - 1);
}
template<typename T>
constexpr ALWAYS_INLINE T MaskTrailingOnesAndLeastSignificantZeroBit(T x) {
return x ^ (x + 1);
}
template<typename T>
constexpr ALWAYS_INLINE int PopCount(T x) {
/* TODO: C++20 std::bit_cast */
using U = typename std::make_unsigned<T>::type;
U u = static_cast<U>(x);
/* TODO: C++20 std::is_constant_evaluated */
if (false) {
/* https://en.wikipedia.org/wiki/Hamming_weight */
constexpr U m1 = U(-1) / 0x03;
constexpr U m2 = U(-1) / 0x05;
constexpr U m4 = U(-1) / 0x11;
u = static_cast<U>(u - ((u >> 1) & m1));
u = static_cast<U>((u & m2) + ((u >> 2) & m2));
u = static_cast<U>((u + (u >> 4)) & m4);
for (size_t i = 0; i < impl::Log2<sizeof(T)>; ++i) {
const size_t shift = (0x1 << i) * BITSIZEOF(u8);
u += u >> shift;
}
return static_cast<int>(u & 0x7Fu);
} else {
if constexpr (std::is_same<U, unsigned long long>::value) {
return __builtin_popcountll(u);
} else if constexpr (std::is_same<U, unsigned long>::value) {
return __builtin_popcountl(u);
} else {
static_assert(sizeof(U) <= sizeof(unsigned int));
return __builtin_popcount(static_cast<unsigned int>(u));
}
}
}
template<typename T>
constexpr ALWAYS_INLINE int CountLeadingZeros(T x) {
/* TODO: C++20 std::is_constant_evaluated */
if (false) {
for (size_t i = 0; i < impl::Log2<BITSIZEOF(T)>; ++i) {
const size_t shift = (0x1 << i);
x |= x >> shift;
}
return PopCount(static_cast<T>(~x));
} else {
/* TODO: C++20 std::bit_cast */
using U = typename std::make_unsigned<T>::type;
const U u = static_cast<U>(x);
if constexpr (std::is_same<U, unsigned long long>::value) {
return __builtin_clzll(u);
} else if constexpr (std::is_same<U, unsigned long>::value) {
return __builtin_clzl(u);
} else if constexpr(std::is_same<U, unsigned int>::value) {
return __builtin_clz(u);
} else {
static_assert(sizeof(U) < sizeof(unsigned int));
constexpr size_t BitDiff = BITSIZEOF(unsigned int) - BITSIZEOF(U);
return __builtin_clz(static_cast<unsigned int>(u)) - BitDiff;
}
}
}
template<typename T>
constexpr ALWAYS_INLINE bool IsPowerOfTwo(T x) {
return x > 0 && ResetLeastSignificantOneBit(x) == 0;
}
template<typename T>
constexpr ALWAYS_INLINE T CeilingPowerOfTwo(T x) {
AMS_ASSERT(x > 0);
return T(1) << (BITSIZEOF(T) - CountLeadingZeros(T(x - 1)));
}
template<typename T>
constexpr ALWAYS_INLINE T FloorPowerOfTwo(T x) {
AMS_ASSERT(x > 0);
return T(1) << (BITSIZEOF(T) - CountLeadingZeros(x) - 1);
}
}