/*
- * Copyright 2015 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.
* @author Tudor Bosman (tudorb@fb.com)
*/
-#ifndef FOLLY_BITS_H_
-#define FOLLY_BITS_H_
+#pragma once
-#if !defined(__clang__) && !defined(_MSC_VER)
+#if !defined(__clang__) && !(defined(_MSC_VER) && (_MSC_VER < 1900))
#define FOLLY_INTRINSIC_CONSTEXPR constexpr
#else
-// GCC is the only compiler with intrinsics constexpr.
+// 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 <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>
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>
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>
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>
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
+ // 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>
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
+ return x ? ((8 * sizeof(unsigned long) - 1) ^ __builtin_clzl(x)) + 1 : 0;
}
template <class T>
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
+ return x ? ((8 * sizeof(unsigned long long) - 1) ^ __builtin_clzll(x)) + 1
+ : 0;
}
template <class T>
std::is_integral<T>::value && std::is_unsigned<T>::value,
T>::type
nextPowTwo(T v) {
- return v ? (1ul << findLastSet(v - 1)) : 1;
+ return v ? (T(1) << 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
+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));
}
#endif
-#define FB_GEN(t, fn) \
-template<> inline t EndianIntBase<t>::swap(t x) { return fn(x); }
+#define FB_GEN(t, fn) \
+ template <> \
+ inline t EndianIntBase<t>::swap(t x) { \
+ return t(fn(std::make_unsigned<t>::type(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
#undef FB_GEN
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-
template <class T>
-struct EndianInt : public detail::EndianIntBase<T> {
+struct EndianInt : public 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); }
+ static T big(T x) {
+ return kIsLittleEndian ? EndianInt::swap(x) : x;
+ }
+ static T little(T x) {
+ return kIsBigEndian ? EndianInt::swap(x) : x;
+ }
};
-#else
-# error Your machine uses a weird endianness!
-#endif /* __BYTE_ORDER__ */
-
} // namespace detail
// big* convert between native and big-endian representations
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__ */
+ static constexpr Order order = kIsLittleEndian ? Order::LITTLE : Order::BIG;
template <class T> static T swap(T x) {
- return detail::EndianInt<T>::swap(x);
+ return folly::detail::EndianInt<T>::swap(x);
}
template <class T> static T big(T x) {
- return detail::EndianInt<T>::big(x);
+ return folly::detail::EndianInt<T>::big(x);
}
template <class T> static T little(T x) {
- return detail::EndianInt<T>::little(x);
+ return folly::detail::EndianInt<T>::little(x);
}
#if !defined(__ANDROID__)
* 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)
+ explicit BitIterator(const BaseIter& iter, size_t bitOff=0)
: bititerator_detail::BitIteratorBase<BaseIter>::type(iter),
- bitOffset_(bitOffset) {
+ bitOffset_(bitOff) {
assert(bitOffset_ < bitsPerBlock());
}
- #pragma GCC diagnostic pop
size_t bitOffset() const {
return bitOffset_;
other.bitOffset_ - bitOffset_;
}
- unsigned int bitOffset_;
+ size_t bitOffset_;
};
/**
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;
+ if (kHasUnalignedAccess) {
+ return static_cast<const Unaligned<T>*>(p)->value;
+ } else {
+ T value;
+ memcpy(&value, p, sizeof(T));
+ return value;
+ }
}
/**
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);
+ 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
-
-#endif /* FOLLY_BITS_H_ */
projects / folly.git / blobdiff