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- // Copyright (c) 2015-2016 The Khronos Group Inc.
- //
- // Licensed under the Apache License, Version 2.0 (the "License");
- // you may not use this file except in compliance with the License.
- // You may obtain a copy of the License at
- //
- // http://www.apache.org/licenses/LICENSE-2.0
- //
- // Unless required by applicable law or agreed to in writing, software
- // distributed under the License is distributed on an "AS IS" BASIS,
- // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- // See the License for the specific language governing permissions and
- // limitations under the License.
- #ifndef LIBSPIRV_UTIL_BITUTILS_H_
- #define LIBSPIRV_UTIL_BITUTILS_H_
- #include <cstdint>
- #include <cstring>
- namespace spvutils {
- // Performs a bitwise copy of source to the destination type Dest.
- template <typename Dest, typename Src>
- Dest BitwiseCast(Src source) {
- Dest dest;
- static_assert(sizeof(source) == sizeof(dest),
- "BitwiseCast: Source and destination must have the same size");
- std::memcpy(static_cast<void*>(&dest), &source, sizeof(dest));
- return dest;
- }
- // SetBits<T, First, Num> returns an integer of type <T> with bits set
- // for position <First> through <First + Num - 1>, counting from the least
- // significant bit. In particular when Num == 0, no positions are set to 1.
- // A static assert will be triggered if First + Num > sizeof(T) * 8, that is,
- // a bit that will not fit in the underlying type is set.
- template <typename T, size_t First = 0, size_t Num = 0>
- struct SetBits {
- static_assert(First < sizeof(T) * 8,
- "Tried to set a bit that is shifted too far.");
- const static T get = (T(1) << First) | SetBits<T, First + 1, Num - 1>::get;
- };
- template <typename T, size_t Last>
- struct SetBits<T, Last, 0> {
- const static T get = T(0);
- };
- // This is all compile-time so we can put our tests right here.
- static_assert(SetBits<uint32_t, 0, 0>::get == uint32_t(0x00000000),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 0, 1>::get == uint32_t(0x00000001),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 31, 1>::get == uint32_t(0x80000000),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 1, 2>::get == uint32_t(0x00000006),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 30, 2>::get == uint32_t(0xc0000000),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 0, 31>::get == uint32_t(0x7FFFFFFF),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 0, 32>::get == uint32_t(0xFFFFFFFF),
- "SetBits failed");
- static_assert(SetBits<uint32_t, 16, 16>::get == uint32_t(0xFFFF0000),
- "SetBits failed");
- static_assert(SetBits<uint64_t, 0, 1>::get == uint64_t(0x0000000000000001LL),
- "SetBits failed");
- static_assert(SetBits<uint64_t, 63, 1>::get == uint64_t(0x8000000000000000LL),
- "SetBits failed");
- static_assert(SetBits<uint64_t, 62, 2>::get == uint64_t(0xc000000000000000LL),
- "SetBits failed");
- static_assert(SetBits<uint64_t, 31, 1>::get == uint64_t(0x0000000080000000LL),
- "SetBits failed");
- static_assert(SetBits<uint64_t, 16, 16>::get == uint64_t(0x00000000FFFF0000LL),
- "SetBits failed");
- } // namespace spvutils
- #endif // LIBSPIRV_UTIL_BITUTILS_H_
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