Adding bitfield.hh

Author: nicolasnoble

src/mips/common/util/bitfield.hh

@@ -0,0 +1,145 @@
+/*
+
+MIT License
+
+Copyright (c) 2025 PCSX-Redux authors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+*/
+
+#include <stdint.h>
+
+#include <concepts>
+#include <type_traits>
+
+#include "util.h"
+
+namespace Utilities {
+
+namespace BitFieldInternal {
+
+template <typename T>
+struct DefaultBitSize {
+    static constexpr unsigned size = sizeof(T) * 8;
+};
+
+template <>
+struct DefaultBitSize<bool> {
+    static constexpr unsigned size = 1;
+};
+
+template <typename... T>
+struct ComputeStorage {
+    static constexpr unsigned size() { return (sizeInBits() + 7) / 8; }
+
+  private:
+    static constexpr unsigned sizeInBits() { return recSize<0, T...>(); }
+    template <unsigned index>
+    static constexpr unsigned recSize() {
+        return 0;
+    }
+    template <unsigned index, typename One, typename... Rest>
+    static constexpr unsigned recSize() {
+        return One::Width + recSize<index + 1, Rest...>();
+    }
+};
+
+template <typename Target, typename... T>
+struct ComputeOffset {
+    static constexpr unsigned offset() { return recOffset<0, T...>(); }
+
+  private:
+    template <unsigned index>
+    static constexpr unsigned recOffset() {
+        return 0;
+    }
+    template <unsigned index, typename One, typename... Rest>
+    static constexpr unsigned recOffset() {
+        if constexpr (std::is_same_v<Target, One>) {
+            return 0;
+        } else {
+            return recOffset<index + 1, Rest...>() + One::Width;
+        }
+    }
+};
+
+}  // namespace BitFieldInternal
+
+template <std::integral T, unsigned width = BitFieldInternal::DefaultBitSize<T>::size>
+struct BitSpan {
+    static constexpr unsigned Width = width;
+    using Underlying = T;
+};
+
+template <typename... T>
+struct BitField {
+    template <typename One>
+    constexpr typename One::Underlying get() {
+        if constexpr (std::is_signed_v<typename One::Underlying>) {
+            return get<BitFieldInternal::ComputeOffset<One, T...>::offset(), One::Width, signed>();
+        } else if constexpr (std::is_unsigned_v<typename One::Underlying>) {
+            return get<BitFieldInternal::ComputeOffset<One, T...>::offset(), One::Width, unsigned>();
+        }
+        return 0;
+    }
+    template <typename One>
+    constexpr void set(typename One::Underlying v) {
+        if constexpr (std::is_signed_v<typename One::Underlying>) {
+            set<BitFieldInternal::ComputeOffset<One, T...>::offset(), One::Width, signed>(v);
+        } else if constexpr (std::is_unsigned_v<typename One::Underlying>) {
+            set<BitFieldInternal::ComputeOffset<One, T...>::offset(), One::Width, unsigned>(v);
+        }
+    }
+
+  private:
+    template <unsigned offset, unsigned width, std::integral U>
+    constexpr U get() {
+        constexpr unsigned firstByteOffset = offset / 8;
+        constexpr unsigned lastByteOffset = (offset + width - 1) / 8;
+        constexpr unsigned shift = offset % 8;
+        constexpr uint32_t mask = (1 << width) - 1;
+        if constexpr ((firstByteOffset % 4) == 0) {
+            return reinterpret_cast<const U*>(storage)[firstByteOffset / 4] >> shift & mask;
+        } else if constexpr ((firstByteOffset % 4) != 0) {
+            return (loadUnaligned<U>(storage + firstByteOffset, lastByteOffset - firstByteOffset + 1) >> shift) & mask;
+        }
+        return 0;
+    }
+    template <unsigned offset, unsigned width, std::integral U>
+    constexpr void set(U v) {
+        constexpr unsigned firstByteOffset = offset / 8;
+        constexpr unsigned lastByteOffset = (offset + width - 1) / 8;
+        constexpr unsigned shift = offset % 8;
+        constexpr uint32_t mask = (1 << width) - 1;
+        if constexpr ((firstByteOffset % 4) == 0) {
+            U* ptr = reinterpret_cast<U*>(storage);
+            ptr[firstByteOffset / 4] &= ~(mask << shift);
+            ptr[firstByteOffset / 4] |= (v & mask) << shift;
+        } else if constexpr ((firstByteOffset % 4) != 0) {
+            U span = loadUnaligned<U>(storage + firstByteOffset, lastByteOffset - firstByteOffset + 1);
+            span &= ~(mask << shift);
+            span |= (v & mask) << shift;
+            storeUnaligned<U>(storage + firstByteOffset, span, lastByteOffset - firstByteOffset + 1);
+        }
+    }
+    uint8_t storage[BitFieldInternal::ComputeStorage<T...>::size()];
+};
+
+}  // namespace Utilities