X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=blobdiff_plain;f=folly%2FBits.h;h=a3cff3ea962f66f3c1ad78d08032833b42a1bb13;hp=6d8b06c2686ec6d5f50078da886caff822ddecf0;hb=da2c859c9c8ce594b8760aae290503e2a33cef7f;hpb=0a9f6eefe125672a5978333c85acc865746841da

diff --git a/folly/Bits.h b/folly/Bits.h
index 6d8b06c2..a3cff3ea 100644
--- a/folly/Bits.h
+++ b/folly/Bits.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,610 +14,4 @@
  * 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)
- */
-
-#ifndef FOLLY_BITS_H_
-#define FOLLY_BITS_H_
-
-#if !defined(__clang__) && !defined(_MSC_VER)
-#define FOLLY_INTRINSIC_CONSTEXPR constexpr
-#else
-// GCC is the only compiler with intrinsics constexpr.
-#define FOLLY_INTRINSIC_CONSTEXPR const
-#endif
-
-#include <folly/Portability.h>
-
-#include <folly/detail/BitsDetail.h>
-#include <folly/detail/BitIteratorDetail.h>
-#include <folly/Likely.h>
-
-#if FOLLY_HAVE_BYTESWAP_H
-# include <byteswap.h>
-#endif
-
-#ifdef _MSC_VER
-# include <intrin.h>
-# pragma intrinsic(_BitScanForward)
-# pragma intrinsic(_BitScanForward64)
-# pragma intrinsic(_BitScanReverse)
-# pragma intrinsic(_BitScanReverse64)
-#endif
-
-#include <cassert>
-#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) {
-#ifdef _MSC_VER
-  unsigned long index;
-  return _BitScanForward(&index, x) ? index : 0;
-#else
-  return __builtin_ffs(x);
-#endif
-}
-
-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) {
-#ifdef _MSC_VER
-  unsigned long index;
-  return _BitScanForward(&index, x) ? index : 0;
-#else
-  return __builtin_ffsl(x);
-#endif
-}
-
-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) {
-#ifdef _MSC_VER
-  unsigned long index;
-  return _BitScanForward64(&index, x) ? index : 0;
-#else
-  return __builtin_ffsll(x);
-#endif
-}
-
-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) {
-#ifdef _MSC_VER
-  unsigned long index;
-  int clz;
-  if (_BitScanReverse(&index, x)) {
-    clz = static_cast<int>(31 - index);
-  } else {
-    clz = 32;
-  }
-  return x ? 8 * sizeof(unsigned int) - clz : 0;
-#else
-  return x ? 8 * sizeof(unsigned int) - __builtin_clz(x) : 0;
-#endif
-}
-
-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) {
-#ifdef _MSC_VER
-  unsigned long index;
-  int clz;
-  if (_BitScanReverse(&index, x)) {
-    clz = static_cast<int>(31 - index);
-  } else {
-    clz = 32;
-  }
-  return x ? 8 * sizeof(unsigned int) - clz : 0;
-#else
-  return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;
-#endif
-}
-
-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) {
-#ifdef _MSC_VER
-  unsigned long index;
-  unsigned long long clz;
-  if (_BitScanReverse(&index, x)) {
-    clz = static_cast<unsigned long long>(63 - index);
-  } else {
-    clz = 64;
-  }
-  return x ? 8 * sizeof(unsigned long long) - clz : 0;
-#else
-  return x ? 8 * sizeof(unsigned long long) - __builtin_clzll(x) : 0;
-#endif
-}
-
-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 ? (1ul << findLastSet(v - 1)) : 1;
-}
-
-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 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 detail::popcountll(x);
-}
-
-/**
- * Endianness detection and manipulation primitives.
- */
-namespace detail {
-
-template <class T>
-struct EndianIntBase {
- public:
-  static T swap(T x);
-};
-
-#ifndef _MSC_VER
-
-/**
- * If we have the bswap_16 macro from byteswap.h, use it; otherwise, provide our
- * own definition.
- */
-#ifdef bswap_16
-# define our_bswap16 bswap_16
-#else
-
-template<class Int16>
-inline constexpr typename std::enable_if<
-  sizeof(Int16) == 2,
-  Int16>::type
-our_bswap16(Int16 x) {
-  return ((x >> 8) & 0xff) | ((x & 0xff) << 8);
-}
-#endif
-
-#endif
-
-#define FB_GEN(t, fn) \
-template<> inline t EndianIntBase<t>::swap(t x) { return fn(x); }
-
-// fn(x) expands to (x) if the second argument is empty, which is exactly
-// what we want for [u]int8_t. Also, gcc 4.7 on Intel doesn't have
-// __builtin_bswap16 for some reason, so we have to provide our own.
-FB_GEN( int8_t,)
-FB_GEN(uint8_t,)
-#ifdef _MSC_VER
-FB_GEN( int64_t, _byteswap_uint64)
-FB_GEN(uint64_t, _byteswap_uint64)
-FB_GEN( int32_t, _byteswap_ulong)
-FB_GEN(uint32_t, _byteswap_ulong)
-FB_GEN( int16_t, _byteswap_ushort)
-FB_GEN(uint16_t, _byteswap_ushort)
-#else
-FB_GEN( int64_t, __builtin_bswap64)
-FB_GEN(uint64_t, __builtin_bswap64)
-FB_GEN( int32_t, __builtin_bswap32)
-FB_GEN(uint32_t, __builtin_bswap32)
-FB_GEN( int16_t, our_bswap16)
-FB_GEN(uint16_t, our_bswap16)
-#endif
-
-#undef FB_GEN
-
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-
-template <class T>
-struct EndianInt : public detail::EndianIntBase<T> {
- public:
-  static T big(T x) { return EndianInt::swap(x); }
-  static T little(T x) { return x; }
-};
-
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-
-template <class T>
-struct EndianInt : public detail::EndianIntBase<T> {
- public:
-  static T big(T x) { return x; }
-  static T little(T x) { return EndianInt::swap(x); }
-};
-
-#else
-# error Your machine uses a weird endianness!
-#endif  /* __BYTE_ORDER__ */
-
-}  // 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 =
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    Order::LITTLE;
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-    Order::BIG;
-#else
-# error Your machine uses a weird endianness!
-#endif  /* __BYTE_ORDER__ */
-
-  template <class T> static T swap(T x) {
-    return detail::EndianInt<T>::swap(x);
-  }
-  template <class T> static T big(T x) {
-    return detail::EndianInt<T>::big(x);
-  }
-  template <class T> static T little(T x) {
-    return 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.
-   */
-  #pragma GCC diagnostic push // bitOffset shadows a member
-  #pragma GCC diagnostic ignored "-Wshadow"
-  explicit BitIterator(const BaseIter& iter, size_t bitOffset=0)
-    : bititerator_detail::BitIteratorBase<BaseIter>::type(iter),
-      bitOffset_(bitOffset) {
-    assert(bitOffset_ < bitsPerBlock());
-  }
-  #pragma GCC diagnostic pop
-
-  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 / 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
-      (other.base_reference() - this->base_reference()) * bitsPerBlock() +
-      (other.bitOffset_ - bitOffset_);
-  }
-
-  unsigned int 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");
-  return static_cast<const Unaligned<T>*>(p)->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");
-  new (p) Unaligned<T>(value);
-}
-
-}  // namespace folly
-
-#endif /* FOLLY_BITS_H_ */
+#include <folly/lang/Bits.h> // @shim