/*
- * Copyright 2016 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.
#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>
-#if FOLLY_HAVE_BYTESWAP_H
-# include <byteswap.h>
-#endif
-
#include <cassert>
+#include <cstring>
#include <cinttypes>
#include <iterator>
#include <limits>
sizeof(T) <= sizeof(unsigned int)),
unsigned int>::type
findFirstSet(T x) {
- return __builtin_ffs(x);
+ return static_cast<unsigned int>(__builtin_ffs(static_cast<int>(x)));
}
template <class T>
sizeof(T) <= sizeof(unsigned long)),
unsigned int>::type
findFirstSet(T x) {
- return __builtin_ffsl(x);
+ return static_cast<unsigned int>(__builtin_ffsl(static_cast<long>(x)));
}
template <class T>
sizeof(T) <= sizeof(unsigned long long)),
unsigned int>::type
findFirstSet(T x) {
- return __builtin_ffsll(x);
+ return static_cast<unsigned int>(__builtin_ffsll(static_cast<long long>(x)));
}
template <class T>
sizeof(T) <= sizeof(unsigned int)),
unsigned int>::type
findLastSet(T x) {
- return x ? 8 * sizeof(unsigned int) - __builtin_clz(x) : 0;
+ // 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) {
- return x ? 8 * sizeof(unsigned long) - __builtin_clzl(x) : 0;
+ 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) {
- return x ? 8 * sizeof(unsigned long long) - __builtin_clzll(x) : 0;
+ return x ? ((8 * sizeof(unsigned long long) - 1) ^ __builtin_clzll(x)) + 1
+ : 0;
}
template <class T>
}
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));
}
sizeof(T) <= sizeof(unsigned int)),
size_t>::type
popcount(T x) {
- return detail::popcount(x);
+ return size_t(detail::popcount(x));
}
template <class T>
sizeof(T) <= sizeof(unsigned long long)),
size_t>::type
popcount(T x) {
- return detail::popcountll(x);
+ return size_t(detail::popcountll(x));
}
/**
*/
namespace detail {
-template <class T>
-struct EndianIntBase {
- public:
- static T swap(T x);
-};
-
-#ifndef _MSC_VER
+template <size_t Size>
+struct uint_types_by_size;
-/**
- * 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); }
+#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 / 8> { \
+ using type = uint##sz##_t; \
+ };
-// 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,)
+FB_GEN(8, 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)
+FB_GEN(64, _byteswap_uint64)
+FB_GEN(32, _byteswap_ulong)
+FB_GEN(16, _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)
+FB_GEN(64, __builtin_bswap64)
+FB_GEN(32, __builtin_bswap32)
+FB_GEN(16, __builtin_bswap16)
#endif
#undef FB_GEN
template <class T>
-struct EndianInt : public EndianIntBase<T> {
- public:
+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<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;
}
void advance(ssize_t n) {
size_t bpb = bitsPerBlock();
- ssize_t blocks = n / bpb;
+ ssize_t blocks = n / ssize_t(bpb);
bitOffset_ += n % bpb;
if (bitOffset_ >= bpb) {
bitOffset_ -= bpb;
}
ssize_t distance_to(const BitIterator& other) const {
- return
- (other.base_reference() - this->base_reference()) * bitsPerBlock() +
- other.bitOffset_ - bitOffset_;
+ return ssize_t(
+ (other.base_reference() - this->base_reference()) * bitsPerBlock() +
+ other.bitOffset_ - bitOffset_);
}
- unsigned int bitOffset_;
+ size_t bitOffset_;
};
/**
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));
projects / folly.git / blobdiff