First Commit

src/common/bit_util.h

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+/* This file is part of the dynarmic project.
+ * Copyright (c) 2016 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+#pragma once
+
+#include <climits>
+
+#include "common/common_types.h"
+
+namespace Dynarmic {
+namespace Common {
+
+/// The size of a type in terms of bits
+template<typename T>
+constexpr size_t BitSize() {
+    return sizeof(T) * CHAR_BIT;
+}
+
+/// Extract bits [begin_bit, end_bit] inclusive from value of type T.
+template<size_t begin_bit, size_t end_bit, typename T>
+constexpr T Bits(const T value) {
+    static_assert(begin_bit < end_bit,
+                  "invalid bit range (position of beginning bit cannot be greater than that of end bit)");
+    static_assert(begin_bit < BitSize<T>(), "begin_bit must be smaller than size of T");
+    static_assert(end_bit < BitSize<T>(), "begin_bit must be smaller than size of T");
+
+    return (value >> begin_bit) & ((1 << (end_bit - begin_bit + 1)) - 1);
+}
+
+/// Extracts a single bit at bit_position from value of type T.
+template<size_t bit_position, typename T>
+constexpr T Bit(const T value) {
+    static_assert(bit_position < BitSize<T>(), "bit_position must be smaller than size of T");
+
+    return (value >> bit_position) & 1;
+}
+
+/// Sign-extends a value that has NBits bits to the full bitwidth of type T.
+template<size_t bit_count, typename T>
+inline T SignExtend(const T value) {
+    static_assert(bit_count <= BitSize<T>(), "bit_count larger than bitsize of T");
+
+    constexpr T mask = static_cast<T>(1ULL << bit_count) - 1;
+    const T signbit = Bit<bit_count - 1>(value);
+    if (signbit != 0) {
+        return value | ~mask;
+    }
+    return value;
+}
+
+} // namespace Common
+} // namespace Dynarmic