X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FBits.h;h=a3cff3ea962f66f3c1ad78d08032833b42a1bb13;hb=d5b67c256c7423d74f4794d7fe421ed239807be4;hp=9795f8f5650f1337d0509c48769dceb1b37fe8c0;hpb=8ff6fe9e5593c1a5a0de24577f1e423fb6eae503;p=folly.git

diff --git a/folly/Bits.h b/folly/Bits.h
index 9795f8f5..a3cff3ea 100644
--- a/folly/Bits.h
+++ b/folly/Bits.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 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.
@@ -14,538 +14,4 @@
  * limitations under the License.
  */
 
-/**
- * Various low-level, bit-manipulation routines.
- *
- * findFirstSet(x)
- *    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)
- *    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, findFirstSet(x) == 1 + floor(log2(x))
- *
- * nextPowTwo(x)
- *    Finds the next power of two >= 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_
-
-#include "folly/Portability.h"
-
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE 1
-#endif
-
-#include "folly/detail/BitIteratorDetail.h"
-#include "folly/Likely.h"
-
-#include <byteswap.h>
-#include <cassert>
-#include <cinttypes>
-#include <cstring>  // for ffs, ffsl, ffsll
-#include <endian.h>
-#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 functions from glibc.
-// We first define these overloads for signed types (because ffs, ffsl, ffsll
-// take int, long, and long long as arguments, respectively) and then
-// define an overload for unsigned that forwards to the overload for the
-// corresponding signed type.
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_signed<T>::value &&
-   (std::numeric_limits<T>::digits <= std::numeric_limits<int>::digits)),
-  unsigned int>::type
-  findFirstSet(T x) {
-  return ::ffs(static_cast<int>(x));
-}
-
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_signed<T>::value &&
-   (std::numeric_limits<T>::digits > std::numeric_limits<int>::digits) &&
-   (std::numeric_limits<T>::digits <= std::numeric_limits<long>::digits)),
-  unsigned int>::type
-  findFirstSet(T x) {
-  return ::ffsl(static_cast<long>(x));
-}
-
-#ifdef FOLLY_HAVE_FFSLL
-
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_signed<T>::value &&
-   (std::numeric_limits<T>::digits > std::numeric_limits<long>::digits) &&
-   (std::numeric_limits<T>::digits <= std::numeric_limits<long long>::digits)),
-  unsigned int>::type
-  findFirstSet(T x) {
-  return ::ffsll(static_cast<long long>(x));
-}
-
-#endif
-
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   !std::is_signed<T>::value),
-  unsigned int>::type
-  findFirstSet(T x) {
-  // Note that conversion from an unsigned type to the corresponding signed
-  // type is technically implementation-defined, but will likely work
-  // on any impementation that uses two's complement.
-  return findFirstSet(static_cast<typename std::make_signed<T>::type>(x));
-}
-
-namespace detail {
-
-// Portable, but likely slow...
-inline unsigned int findLastSetPortable(uint64_t x) {
-  unsigned int r = (x != 0);  // 1-based index, except for x==0
-  while (x >>= 1) {
-    ++r;
-  }
-  return r;
-}
-
-}  // namespace detail
-
-#ifdef __GNUC__
-
-// findLastSet: return the 1-based index of the highest bit set
-// for x > 0, findLastSet(x) == 1 + floor(log2(x))
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_unsigned<T>::value &&
-   (std::numeric_limits<T>::digits <=
-    std::numeric_limits<unsigned int>::digits)),
-  unsigned int>::type
-  findLastSet(T x) {
-  return x ? 8 * sizeof(unsigned int) - __builtin_clz(x) : 0;
-}
-
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_unsigned<T>::value &&
-   (std::numeric_limits<T>::digits >
-    std::numeric_limits<unsigned int>::digits) &&
-   (std::numeric_limits<T>::digits <=
-    std::numeric_limits<unsigned long>::digits)),
-  unsigned int>::type
-  findLastSet(T x) {
-  return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;
-}
-
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_unsigned<T>::value &&
-   (std::numeric_limits<T>::digits >
-    std::numeric_limits<unsigned long>::digits) &&
-   (std::numeric_limits<T>::digits <=
-    std::numeric_limits<unsigned long long>::digits)),
-  unsigned int>::type
-  findLastSet(T x) {
-  return x ? 8 * sizeof(unsigned long long) - __builtin_clzll(x) : 0;
-}
-
-#else  /* !__GNUC__ */
-
-template <class T>
-typename std::enable_if<
-  (std::is_integral<T>::value &&
-   std::is_unsigned<T>::value),
-  unsigned int>::type
-  findLastSet(T x) {
-  return detail:findLastSetPortable(x);
-}
-
-#endif
-
-template <class T>
-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));
-}
-
-namespace detail {
-
-template <class T>
-inline
-typename std::enable_if<
-  std::is_integral<T>::value && std::is_unsigned<T>::value,
-  T>::type
-nextPowTwoPortable(T v) {
-  if (UNLIKELY(v == 0)) {
-    return 1;
-  }
-
-  --v;
-  for (uint32_t i = 1; i < sizeof(T) * 8; i <<= 8) {
-    v |= (v >> i);
-    v |= (v >> (i << 1));
-    v |= (v >> (i << 2));
-    v |= (v >> (i << 3));
-    v |= (v >> (i << 4));
-    v |= (v >> (i << 5));
-    v |= (v >> (i << 6));
-    v |= (v >> (i << 7));
-  }
-  return v + 1;
-}
-
-}  // namespace detail
-
-#ifdef __GNUC__
-
-template <class T>
-inline
-typename std::enable_if<
-  std::is_integral<T>::value && std::is_unsigned<T>::value,
-  T>::type
-nextPowTwo(T v) {
-  if (UNLIKELY(v == 0)) {
-    return 1;
-  }
-  return 1ul << findLastSet(v - 1);
-}
-
-#else /* __GNUC__ */
-
-template <class T>
-inline
-typename std::enable_if<
-  std::is_integral<T>::value && std::is_unsigned<T>::value,
-  T>::type
-nextPowTwo(T v) {
-  return detail::nextPowTwoPortable(v);
-}
-
-#endif /* __GNUC__ */
-
-
-
-/**
- * Endianness detection and manipulation primitives.
- */
-namespace detail {
-
-template <class T>
-struct EndianIntBase {
- public:
-  static T swap(T x);
-};
-
-#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
-FB_GEN( int8_t,)
-FB_GEN(uint8_t,)
-FB_GEN( int64_t, bswap_64)
-FB_GEN(uint64_t, bswap_64)
-FB_GEN( int32_t, bswap_32)
-FB_GEN(uint32_t, bswap_32)
-FB_GEN( int16_t, bswap_16)
-FB_GEN(uint16_t, bswap_16)
-
-#undef FB_GEN
-
-#if __BYTE_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 == __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:
-  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);
-  }
-
-  FB_GEN(64)
-  FB_GEN(32)
-  FB_GEN(16)
-  FB_GEN(8)
-};
-
-#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 size_t 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 bitOffset=0)
-    : bititerator_detail::BitIteratorBase<BaseIter>::type(iter),
-      bitOffset_(bitOffset) {
-    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 / 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_);
-  }
-
-  ssize_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;
-}
-
-
-namespace detail {
-
-template <class T, class Enable=void> struct Unaligned;
-
-template <class T>
-struct Unaligned<
-  T,
-  typename std::enable_if<std::is_pod<T>::value>::type> {
-  T value;
-} __attribute__((packed));
-
-}  // namespace detail
-
-/**
- * Read an unaligned value of type T and return it.
- */
-template <class T>
-inline T loadUnaligned(const void* p) {
-  static_assert(alignof(detail::Unaligned<T>) == 1, "Invalid alignment");
-  return static_cast<const detail::Unaligned<T>*>(p)->value;
-}
-
-/**
- * Write an unaligned value of type T.
- */
-template <class T>
-inline void storeUnaligned(void* p, T value) {
-  static_assert(alignof(detail::Unaligned<T>) == 1, "Invalid alignment");
-  static_cast<detail::Unaligned<T>*>(p)->value = value;
-}
-
-}  // namespace folly
-
-#endif /* FOLLY_BITS_H_ */
-
+#include <folly/lang/Bits.h> // @shim