1 // Copyright (c) 2015-2016 The Khronos Group Inc. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef LIBSPIRV_UTIL_BITUTILS_H_ 16 #define LIBSPIRV_UTIL_BITUTILS_H_ 17 18 #include <cstdint> 19 #include <cstring> 20 21 namespace spvutils { 22 23 // Performs a bitwise copy of source to the destination type Dest. 24 template <typename Dest, typename Src> 25 Dest BitwiseCast(Src source) { 26 Dest dest; 27 static_assert(sizeof(source) == sizeof(dest), 28 "BitwiseCast: Source and destination must have the same size"); 29 std::memcpy(&dest, &source, sizeof(dest)); 30 return dest; 31 } 32 33 // SetBits<T, First, Num> returns an integer of type <T> with bits set 34 // for position <First> through <First + Num - 1>, counting from the least 35 // significant bit. In particular when Num == 0, no positions are set to 1. 36 // A static assert will be triggered if First + Num > sizeof(T) * 8, that is, 37 // a bit that will not fit in the underlying type is set. 38 template <typename T, size_t First = 0, size_t Num = 0> 39 struct SetBits { 40 static_assert(First < sizeof(T) * 8, 41 "Tried to set a bit that is shifted too far."); 42 const static T get = (T(1) << First) | SetBits<T, First + 1, Num - 1>::get; 43 }; 44 45 template <typename T, size_t Last> 46 struct SetBits<T, Last, 0> { 47 const static T get = T(0); 48 }; 49 50 // This is all compile-time so we can put our tests right here. 51 static_assert(SetBits<uint32_t, 0, 0>::get == uint32_t(0x00000000), 52 "SetBits failed"); 53 static_assert(SetBits<uint32_t, 0, 1>::get == uint32_t(0x00000001), 54 "SetBits failed"); 55 static_assert(SetBits<uint32_t, 31, 1>::get == uint32_t(0x80000000), 56 "SetBits failed"); 57 static_assert(SetBits<uint32_t, 1, 2>::get == uint32_t(0x00000006), 58 "SetBits failed"); 59 static_assert(SetBits<uint32_t, 30, 2>::get == uint32_t(0xc0000000), 60 "SetBits failed"); 61 static_assert(SetBits<uint32_t, 0, 31>::get == uint32_t(0x7FFFFFFF), 62 "SetBits failed"); 63 static_assert(SetBits<uint32_t, 0, 32>::get == uint32_t(0xFFFFFFFF), 64 "SetBits failed"); 65 static_assert(SetBits<uint32_t, 16, 16>::get == uint32_t(0xFFFF0000), 66 "SetBits failed"); 67 68 static_assert(SetBits<uint64_t, 0, 1>::get == uint64_t(0x0000000000000001LL), 69 "SetBits failed"); 70 static_assert(SetBits<uint64_t, 63, 1>::get == uint64_t(0x8000000000000000LL), 71 "SetBits failed"); 72 static_assert(SetBits<uint64_t, 62, 2>::get == uint64_t(0xc000000000000000LL), 73 "SetBits failed"); 74 static_assert(SetBits<uint64_t, 31, 1>::get == uint64_t(0x0000000080000000LL), 75 "SetBits failed"); 76 static_assert(SetBits<uint64_t, 16, 16>::get == uint64_t(0x00000000FFFF0000LL), 77 "SetBits failed"); 78 79 } // namespace spvutils 80 81 #endif // LIBSPIRV_UTIL_BITUTILS_H_ 82
