#include <folly/portability/Builtins.h>
#include <folly/Assume.h>
-#include <folly/detail/BitsDetail.h>
#include <folly/detail/BitIteratorDetail.h>
#include <folly/Likely.h>
#include <cassert>
+#include <cstring>
#include <cinttypes>
#include <iterator>
#include <limits>
sizeof(T) <= sizeof(unsigned int)),
size_t>::type
popcount(T x) {
- return size_t(detail::popcount(x));
+ return size_t(__builtin_popcount(x));
}
template <class T>
sizeof(T) <= sizeof(unsigned long long)),
size_t>::type
popcount(T x) {
- return size_t(detail::popcountll(x));
+ return size_t(__builtin_popcountll(x));
}
/**
*/
namespace detail {
-template <class T>
-struct EndianIntBase {
- public:
- static T swap(T x);
-};
+template <size_t Size>
+struct uint_types_by_size;
-#define FB_GEN(t, fn) \
- template <> \
- inline t EndianIntBase<t>::swap(t x) { \
- return t(fn(std::make_unsigned<t>::type(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.
-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, __builtin_bswap16)
-FB_GEN(uint16_t, __builtin_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;
}