common: Port BitSet from Mesosphere.

src/common/CMakeLists.txt

@@ -104,6 +104,7 @@ add_library(common STATIC
     detached_tasks.h
     bit_cast.h
     bit_field.h
+    bit_set.h
     bit_util.h
     cityhash.cpp
     cityhash.h

src/common/bit_set.h

+/*
+ * Copyright (c) 2018-2020 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "common/alignment.h"
+#include "common/bit_util.h"
+#include "common/common_types.h"
+
+namespace Common {
+
+namespace impl {
+
+#define BITSIZEOF(x) (sizeof(x) * CHAR_BIT)
+
+template <typename Storage, size_t N>
+class BitSet {
+private:
+    static_assert(std::is_integral<Storage>::value);
+    static_assert(std::is_unsigned<Storage>::value);
+    static_assert(sizeof(Storage) <= sizeof(u64));
+
+    static constexpr size_t FlagsPerWord = BITSIZEOF(Storage);
+    static constexpr size_t NumWords = AlignUp(N, FlagsPerWord) / FlagsPerWord;
+
+    static constexpr auto CountLeadingZeroImpl(Storage word) {
+        return CountLeadingZeroes64(static_cast<unsigned long long>(word)) -
+               (BITSIZEOF(unsigned long long) - FlagsPerWord);
+    }
+
+    static constexpr Storage GetBitMask(size_t bit) {
+        return Storage(1) << (FlagsPerWord - 1 - bit);
+    }
+
+private:
+    Storage words[NumWords];
+
+public:
+    constexpr BitSet() : words() { /* ... */
+    }
+
+    constexpr void SetBit(size_t i) {
+        this->words[i / FlagsPerWord] |= GetBitMask(i % FlagsPerWord);
+    }
+
+    constexpr void ClearBit(size_t i) {
+        this->words[i / FlagsPerWord] &= ~GetBitMask(i % FlagsPerWord);
+    }
+
+    constexpr size_t CountLeadingZero() const {
+        for (size_t i = 0; i < NumWords; i++) {
+            if (this->words[i]) {
+                return FlagsPerWord * i + CountLeadingZeroImpl(this->words[i]);
+            }
+        }
+        return FlagsPerWord * NumWords;
+    }
+
+    constexpr size_t GetNextSet(size_t n) const {
+        for (size_t i = (n + 1) / FlagsPerWord; i < NumWords; i++) {
+            Storage word = this->words[i];
+            if (!IsAligned(n + 1, FlagsPerWord)) {
+                word &= GetBitMask(n % FlagsPerWord) - 1;
+            }
+            if (word) {
+                return FlagsPerWord * i + CountLeadingZeroImpl(word);
+            }
+        }
+        return FlagsPerWord * NumWords;
+    }
+};
+
+} // namespace impl
+
+template <size_t N>
+using BitSet8 = impl::BitSet<u8, N>;
+
+template <size_t N>
+using BitSet16 = impl::BitSet<u16, N>;
+
+template <size_t N>
+using BitSet32 = impl::BitSet<u32, N>;
+
+template <size_t N>
+using BitSet64 = impl::BitSet<u64, N>;
+
+} // namespace Common