/*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
/**
* Various low-level, bit-manipulation routines.
*
- * findFirstSet(x)
+ * 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)
+ * 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
*
- * nextPowTwo(x)
- * Finds the next power of two >= x.
- *
* Endian
* convert between native, big, and little endian representation
* Endian::big(x) big <-> native
#include "folly/Portability.h"
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE 1
-#endif
-
#ifndef __GNUC__
#error GCC required
#endif
+#ifndef __clang__
+#define FOLLY_INTRINSIC_CONSTEXPR constexpr
+#else
+// Unlike GCC, in Clang (as of 3.2) intrinsics aren't constexpr.
+#define FOLLY_INTRINSIC_CONSTEXPR const
+#endif
+
+#ifndef FOLLY_NO_CONFIG
+#include "folly/folly-config.h"
+#endif
+
#include "folly/detail/BitsDetail.h"
#include "folly/detail/BitIteratorDetail.h"
#include "folly/Likely.h"
-#include <byteswap.h>
+#if FOLLY_HAVE_BYTESWAP_H
+# include <byteswap.h>
+#endif
+
#include <cassert>
#include <cinttypes>
-#include <endian.h>
#include <iterator>
#include <limits>
#include <type_traits>
// 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 &&
}
template <class T>
+inline FOLLY_INTRINSIC_CONSTEXPR
typename std::enable_if<
(std::is_integral<T>::value &&
std::is_unsigned<T>::value &&
}
template <class T>
+inline FOLLY_INTRINSIC_CONSTEXPR
typename std::enable_if<
(std::is_integral<T>::value &&
std::is_unsigned<T>::value &&
}
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: 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 &&
}
template <class T>
+inline FOLLY_INTRINSIC_CONSTEXPR
typename std::enable_if<
(std::is_integral<T>::value &&
std::is_unsigned<T>::value &&
}
template <class T>
+inline FOLLY_INTRINSIC_CONSTEXPR
typename std::enable_if<
(std::is_integral<T>::value &&
std::is_unsigned<T>::value &&
}
template <class T>
+inline FOLLY_INTRINSIC_CONSTEXPR
typename std::enable_if<
(std::is_integral<T>::value &&
std::is_signed<T>::value),
}
template <class T>
-inline
+inline FOLLY_INTRINSIC_CONSTEXPR
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);
+ 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));
}
/**
static T swap(T x);
};
+/**
+ * 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
+
#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
+// 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,)
-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)
+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)
#undef FB_GEN
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
template <class T>
struct EndianInt : public detail::EndianIntBase<T> {
static T little(T x) { return x; }
};
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
template <class T>
struct EndianInt : public detail::EndianIntBase<T> {
#else
# error Your machine uses a weird endianness!
-#endif /* __BYTE_ORDER */
+#endif /* __BYTE_ORDER__ */
} // namespace detail
};
static constexpr Order order =
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
Order::LITTLE;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
Order::BIG;
#else
# error Your machine uses a weird endianness!
-#endif /* __BYTE_ORDER */
+#endif /* __BYTE_ORDER__ */
template <class T> static T swap(T x) {
return detail::EndianInt<T>::swap(x);
* 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_;
struct Unaligned<
T,
typename std::enable_if<std::is_pod<T>::value>::type> {
- Unaligned() { } // uninitialized
+ Unaligned() = default; // uninitialized
/* implicit */ Unaligned(T v) : value(v) { }
T value;
} __attribute__((packed));
} // namespace folly
#endif /* FOLLY_BITS_H_ */
-
projects / folly.git / blobdiff