* limitations under the License.
*/
-/**
- * Various low-level, bit-manipulation routines.
- *
- * findFirstSet(x) [constexpr]
- * find first (least significant) bit set in a value of an integral type,
- * 1-based (like ffs()). 0 = no bits are set (x == 0)
- *
- * findLastSet(x) [constexpr]
- * find last (most significant) bit set in a value of an integral type,
- * 1-based. 0 = no bits are set (x == 0)
- * for x != 0, findLastSet(x) == 1 + floor(log2(x))
- *
- * nextPowTwo(x) [constexpr]
- * Finds the next power of two >= x.
- *
- * isPowTwo(x) [constexpr]
- * return true iff x is a power of two
- *
- * popcount(x)
- * return the number of 1 bits in x
- *
- * Endian
- * convert between native, big, and little endian representation
- * Endian::big(x) big <-> native
- * Endian::little(x) little <-> native
- * Endian::swap(x) big <-> little
- *
- * BitIterator
- * Wrapper around an iterator over an integral type that iterates
- * over its underlying bits in MSb to LSb order
- *
- * findFirstSet(BitIterator begin, BitIterator end)
- * return a BitIterator pointing to the first 1 bit in [begin, end), or
- * end if all bits in [begin, end) are 0
- *
- * @author Tudor Bosman (tudorb@fb.com)
- */
-
-#pragma once
-
-#if !defined(__clang__) && !(defined(_MSC_VER) && (_MSC_VER < 1900))
-#define FOLLY_INTRINSIC_CONSTEXPR constexpr
-#else
-// GCC and MSVC 2015+ are the only compilers with
-// intrinsics constexpr.
-#define FOLLY_INTRINSIC_CONSTEXPR const
-#endif
-
-#include <folly/Portability.h>
-#include <folly/portability/Builtins.h>
-
-#include <folly/Assume.h>
-#include <folly/detail/BitsDetail.h>
-#include <folly/detail/BitIteratorDetail.h>
-#include <folly/Likely.h>
-
-#include <cassert>
-#include <cstring>
-#include <cinttypes>
-#include <iterator>
-#include <limits>
-#include <type_traits>
-#include <boost/iterator/iterator_adaptor.hpp>
-#include <stdint.h>
-
-namespace folly {
-
-// Generate overloads for findFirstSet as wrappers around
-// appropriate ffs, ffsl, ffsll gcc builtins
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) <= sizeof(unsigned int)),
- unsigned int>::type
- findFirstSet(T x) {
- return static_cast<unsigned int>(__builtin_ffs(static_cast<int>(x)));
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) > sizeof(unsigned int) &&
- sizeof(T) <= sizeof(unsigned long)),
- unsigned int>::type
- findFirstSet(T x) {
- return static_cast<unsigned int>(__builtin_ffsl(static_cast<long>(x)));
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) > sizeof(unsigned long) &&
- sizeof(T) <= sizeof(unsigned long long)),
- unsigned int>::type
- findFirstSet(T x) {
- return static_cast<unsigned int>(__builtin_ffsll(static_cast<long long>(x)));
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value && std::is_signed<T>::value),
- unsigned int>::type
- findFirstSet(T x) {
- // Note that conversion from a signed type to the corresponding unsigned
- // type is technically implementation-defined, but will likely work
- // on any impementation that uses two's complement.
- return findFirstSet(static_cast<typename std::make_unsigned<T>::type>(x));
-}
-
-// findLastSet: return the 1-based index of the highest bit set
-// for x > 0, findLastSet(x) == 1 + floor(log2(x))
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) <= sizeof(unsigned int)),
- unsigned int>::type
- findLastSet(T x) {
- // If X is a power of two X - Y = ((X - 1) ^ Y) + 1. Doing this transformation
- // allows GCC to remove its own xor that it adds to implement clz using bsr
- return x ? ((8 * sizeof(unsigned int) - 1) ^ __builtin_clz(x)) + 1 : 0;
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) > sizeof(unsigned int) &&
- sizeof(T) <= sizeof(unsigned long)),
- unsigned int>::type
- findLastSet(T x) {
- return x ? ((8 * sizeof(unsigned long) - 1) ^ __builtin_clzl(x)) + 1 : 0;
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) > sizeof(unsigned long) &&
- sizeof(T) <= sizeof(unsigned long long)),
- unsigned int>::type
- findLastSet(T x) {
- return x ? ((8 * sizeof(unsigned long long) - 1) ^ __builtin_clzll(x)) + 1
- : 0;
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_signed<T>::value),
- unsigned int>::type
- findLastSet(T x) {
- return findLastSet(static_cast<typename std::make_unsigned<T>::type>(x));
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR
-typename std::enable_if<
- std::is_integral<T>::value && std::is_unsigned<T>::value,
- T>::type
-nextPowTwo(T v) {
- return v ? (T(1) << findLastSet(v - 1)) : 1;
-}
-
-template <class T>
-inline FOLLY_INTRINSIC_CONSTEXPR typename std::
- enable_if<std::is_integral<T>::value && std::is_unsigned<T>::value, T>::type
- prevPowTwo(T v) {
- return v ? (T(1) << (findLastSet(v) - 1)) : 0;
-}
-
-template <class T>
-inline constexpr typename std::enable_if<
- std::is_integral<T>::value && std::is_unsigned<T>::value,
- bool>::type
-isPowTwo(T v) {
- return (v != 0) && !(v & (v - 1));
-}
-
-/**
- * Population count
- */
-template <class T>
-inline typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) <= sizeof(unsigned int)),
- size_t>::type
- popcount(T x) {
- return size_t(detail::popcount(x));
-}
-
-template <class T>
-inline typename std::enable_if<
- (std::is_integral<T>::value &&
- std::is_unsigned<T>::value &&
- sizeof(T) > sizeof(unsigned int) &&
- sizeof(T) <= sizeof(unsigned long long)),
- size_t>::type
- popcount(T x) {
- return size_t(detail::popcountll(x));
-}
-
-/**
- * Endianness detection and manipulation primitives.
- */
-namespace detail {
-
-template <size_t Size>
-struct uint_types_by_size;
-
-#define FB_GEN(sz, fn) \
- static inline uint##sz##_t byteswap_gen(uint##sz##_t v) { \
- return fn(v); \
- } \
- template <> \
- struct uint_types_by_size<sz> { \
- using type = uint##sz##_t; \
- };
-
-FB_GEN(8, uint8_t)
-#ifdef _MSC_VER
-FB_GEN(64, _byteswap_uint64)
-FB_GEN(32, _byteswap_ulong)
-FB_GEN(16, _byteswap_ushort)
-#else
-FB_GEN(64, __builtin_bswap64)
-FB_GEN(32, __builtin_bswap32)
-FB_GEN(16, __builtin_bswap16)
-#endif
-
-#undef FB_GEN
-
-template <class T>
-struct EndianInt {
- static_assert(
- (std::is_integral<T>::value && !std::is_same<T, bool>::value) ||
- std::is_floating_point<T>::value,
- "template type parameter must be non-bool integral or floating point");
- static T swap(T x) {
- // we implement this with memcpy because that is defined behavior in C++
- // we rely on compilers to optimize away the memcpy calls
- constexpr auto s = sizeof(T);
- using B = typename uint_types_by_size<8 * s>::type;
- B b;
- std::memcpy(&b, &x, s);
- b = byteswap_gen(b);
- std::memcpy(&x, &b, s);
- return x;
- }
- static T big(T x) {
- return kIsLittleEndian ? EndianInt::swap(x) : x;
- }
- static T little(T x) {
- return kIsBigEndian ? EndianInt::swap(x) : x;
- }
-};
-
-} // namespace detail
-
-// big* convert between native and big-endian representations
-// little* convert between native and little-endian representations
-// swap* convert between big-endian and little-endian representations
-//
-// ntohs, htons == big16
-// ntohl, htonl == big32
-#define FB_GEN1(fn, t, sz) \
- static t fn##sz(t x) { return fn<t>(x); } \
-
-#define FB_GEN2(t, sz) \
- FB_GEN1(swap, t, sz) \
- FB_GEN1(big, t, sz) \
- FB_GEN1(little, t, sz)
-
-#define FB_GEN(sz) \
- FB_GEN2(uint##sz##_t, sz) \
- FB_GEN2(int##sz##_t, sz)
-
-class Endian {
- public:
- enum class Order : uint8_t {
- LITTLE,
- BIG
- };
-
- static constexpr Order order = kIsLittleEndian ? Order::LITTLE : Order::BIG;
-
- template <class T> static T swap(T x) {
- return folly::detail::EndianInt<T>::swap(x);
- }
- template <class T> static T big(T x) {
- return folly::detail::EndianInt<T>::big(x);
- }
- template <class T> static T little(T x) {
- return folly::detail::EndianInt<T>::little(x);
- }
-
-#if !defined(__ANDROID__)
- FB_GEN(64)
- FB_GEN(32)
- FB_GEN(16)
- FB_GEN(8)
-#endif
-};
-
-#undef FB_GEN
-#undef FB_GEN2
-#undef FB_GEN1
-
-/**
- * Fast bit iteration facility.
- */
-
-
-template <class BaseIter> class BitIterator;
-template <class BaseIter>
-BitIterator<BaseIter> findFirstSet(BitIterator<BaseIter>,
- BitIterator<BaseIter>);
-/**
- * Wrapper around an iterator over an integer type that iterates
- * over its underlying bits in LSb to MSb order.
- *
- * BitIterator models the same iterator concepts as the base iterator.
- */
-template <class BaseIter>
-class BitIterator
- : public bititerator_detail::BitIteratorBase<BaseIter>::type {
- public:
- /**
- * Return the number of bits in an element of the underlying iterator.
- */
- static unsigned int bitsPerBlock() {
- return std::numeric_limits<
- typename std::make_unsigned<
- typename std::iterator_traits<BaseIter>::value_type
- >::type
- >::digits;
- }
-
- /**
- * Construct a BitIterator that points at a given bit offset (default 0)
- * in iter.
- */
- explicit BitIterator(const BaseIter& iter, size_t bitOff=0)
- : bititerator_detail::BitIteratorBase<BaseIter>::type(iter),
- bitOffset_(bitOff) {
- assert(bitOffset_ < bitsPerBlock());
- }
-
- size_t bitOffset() const {
- return bitOffset_;
- }
-
- void advanceToNextBlock() {
- bitOffset_ = 0;
- ++this->base_reference();
- }
-
- BitIterator& operator=(const BaseIter& other) {
- this->~BitIterator();
- new (this) BitIterator(other);
- return *this;
- }
-
- private:
- friend class boost::iterator_core_access;
- friend BitIterator findFirstSet<>(BitIterator, BitIterator);
-
- typedef bititerator_detail::BitReference<
- typename std::iterator_traits<BaseIter>::reference,
- typename std::iterator_traits<BaseIter>::value_type
- > BitRef;
-
- void advanceInBlock(size_t n) {
- bitOffset_ += n;
- assert(bitOffset_ < bitsPerBlock());
- }
-
- BitRef dereference() const {
- return BitRef(*this->base_reference(), bitOffset_);
- }
-
- void advance(ssize_t n) {
- size_t bpb = bitsPerBlock();
- ssize_t blocks = n / ssize_t(bpb);
- bitOffset_ += n % bpb;
- if (bitOffset_ >= bpb) {
- bitOffset_ -= bpb;
- ++blocks;
- }
- this->base_reference() += blocks;
- }
-
- void increment() {
- if (++bitOffset_ == bitsPerBlock()) {
- advanceToNextBlock();
- }
- }
-
- void decrement() {
- if (bitOffset_-- == 0) {
- bitOffset_ = bitsPerBlock() - 1;
- --this->base_reference();
- }
- }
-
- bool equal(const BitIterator& other) const {
- return (bitOffset_ == other.bitOffset_ &&
- this->base_reference() == other.base_reference());
- }
-
- ssize_t distance_to(const BitIterator& other) const {
- return ssize_t(
- (other.base_reference() - this->base_reference()) * bitsPerBlock() +
- other.bitOffset_ - bitOffset_);
- }
-
- size_t bitOffset_;
-};
-
-/**
- * Helper function, so you can write
- * auto bi = makeBitIterator(container.begin());
- */
-template <class BaseIter>
-BitIterator<BaseIter> makeBitIterator(const BaseIter& iter) {
- return BitIterator<BaseIter>(iter);
-}
-
-
-/**
- * Find first bit set in a range of bit iterators.
- * 4.5x faster than the obvious std::find(begin, end, true);
- */
-template <class BaseIter>
-BitIterator<BaseIter> findFirstSet(BitIterator<BaseIter> begin,
- BitIterator<BaseIter> end) {
- // shortcut to avoid ugly static_cast<>
- static const typename BaseIter::value_type one = 1;
-
- while (begin.base() != end.base()) {
- typename BaseIter::value_type v = *begin.base();
- // mask out the bits that don't matter (< begin.bitOffset)
- v &= ~((one << begin.bitOffset()) - 1);
- size_t firstSet = findFirstSet(v);
- if (firstSet) {
- --firstSet; // now it's 0-based
- assert(firstSet >= begin.bitOffset());
- begin.advanceInBlock(firstSet - begin.bitOffset());
- return begin;
- }
- begin.advanceToNextBlock();
- }
-
- // now begin points to the same block as end
- if (end.bitOffset() != 0) { // assume end is dereferenceable
- typename BaseIter::value_type v = *begin.base();
- // mask out the bits that don't matter (< begin.bitOffset)
- v &= ~((one << begin.bitOffset()) - 1);
- // mask out the bits that don't matter (>= end.bitOffset)
- v &= (one << end.bitOffset()) - 1;
- size_t firstSet = findFirstSet(v);
- if (firstSet) {
- --firstSet; // now it's 0-based
- assert(firstSet >= begin.bitOffset());
- begin.advanceInBlock(firstSet - begin.bitOffset());
- return begin;
- }
- }
-
- return end;
-}
-
-
-template <class T, class Enable=void> struct Unaligned;
-
-/**
- * Representation of an unaligned value of a POD type.
- */
-FOLLY_PACK_PUSH
-template <class T>
-struct Unaligned<
- T,
- typename std::enable_if<std::is_pod<T>::value>::type> {
- Unaligned() = default; // uninitialized
- /* implicit */ Unaligned(T v) : value(v) { }
- T value;
-} FOLLY_PACK_ATTR;
-FOLLY_PACK_POP
-
-/**
- * Read an unaligned value of type T and return it.
- */
-template <class T>
-inline T loadUnaligned(const void* p) {
- static_assert(sizeof(Unaligned<T>) == sizeof(T), "Invalid unaligned size");
- static_assert(alignof(Unaligned<T>) == 1, "Invalid alignment");
- if (kHasUnalignedAccess) {
- return static_cast<const Unaligned<T>*>(p)->value;
- } else {
- T value;
- memcpy(&value, p, sizeof(T));
- return value;
- }
-}
-
-/**
- * Write an unaligned value of type T.
- */
-template <class T>
-inline void storeUnaligned(void* p, T value) {
- static_assert(sizeof(Unaligned<T>) == sizeof(T), "Invalid unaligned size");
- static_assert(alignof(Unaligned<T>) == 1, "Invalid alignment");
- if (kHasUnalignedAccess) {
- // Prior to C++14, the spec says that a placement new like this
- // is required to check that p is not nullptr, and to do nothing
- // if p is a nullptr. By assuming it's not a nullptr, we get a
- // nice loud segfault in optimized builds if p is nullptr, rather
- // than just silently doing nothing.
- folly::assume(p != nullptr);
- new (p) Unaligned<T>(value);
- } else {
- memcpy(p, &value, sizeof(T));
- }
-}
-
-} // namespace folly
+#include <folly/lang/Bits.h> // @shim