From e1adbb6dbafee45fe01f5c47554d2ed19f918e84 Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Thu, 30 Jan 2020 17:45:54 -0800
Subject: [PATCH] util: add BitSet

---
 libraries/libvapours/include/vapours/util.hpp |  1 +
 .../include/vapours/util/util_bitset.hpp      | 91 +++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 libraries/libvapours/include/vapours/util/util_bitset.hpp

diff --git a/libraries/libvapours/include/vapours/util.hpp b/libraries/libvapours/include/vapours/util.hpp
index 53bf9eac3..5656d33e3 100644
--- a/libraries/libvapours/include/vapours/util.hpp
+++ b/libraries/libvapours/include/vapours/util.hpp
@@ -21,6 +21,7 @@
 #include "util/util_size.hpp"
 #include "util/util_fourcc.hpp"
 #include "util/util_bitpack.hpp"
+#include "util/util_bitset.hpp"
 #include "util/util_scope_guard.hpp"
 #include "util/util_typed_storage.hpp"
 #include "util/util_intrusive_list.hpp"
diff --git a/libraries/libvapours/include/vapours/util/util_bitset.hpp b/libraries/libvapours/include/vapours/util/util_bitset.hpp
new file mode 100644
index 000000000..e3f9ae732
--- /dev/null
+++ b/libraries/libvapours/include/vapours/util/util_bitset.hpp
@@ -0,0 +1,91 @@
+/*
+ * 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 "../defines.hpp"
+
+namespace ams::util {
+
+    namespace impl {
+
+        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     = util::AlignUp(N, FlagsPerWord) / FlagsPerWord;
+
+                static constexpr ALWAYS_INLINE auto CountLeadingZeroImpl(Storage word) {
+                    return __builtin_clzll(static_cast<unsigned long long>(word)) - (BITSIZEOF(unsigned long long) - FlagsPerWord);
+                }
+
+                static constexpr ALWAYS_INLINE Storage GetBitMask(size_t bit) {
+                    return Storage(1) << (FlagsPerWord - 1 - bit);
+                }
+            private:
+                Storage words[NumWords];
+            public:
+                constexpr ALWAYS_INLINE BitSet() : words() { /* ... */ }
+
+                constexpr ALWAYS_INLINE void SetBit(size_t i) {
+                    this->words[i / FlagsPerWord] |= GetBitMask(i % FlagsPerWord);
+                }
+
+                constexpr ALWAYS_INLINE void ClearBit(size_t i) {
+                    this->words[i / FlagsPerWord] &= ~GetBitMask(i % FlagsPerWord);
+                }
+
+                constexpr ALWAYS_INLINE 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 ALWAYS_INLINE size_t GetNextSet(size_t n) const {
+                    for (size_t i = (n + 1) / FlagsPerWord; i < NumWords; i++) {
+                        Storage word = this->words[i];
+                        if (!util::IsAligned(n + 1, FlagsPerWord)) {
+                            word &= GetBitMask(n % FlagsPerWord) - 1;
+                        }
+                        if (word) {
+                            return FlagsPerWord * i + CountLeadingZeroImpl(word);
+                        }
+                    }
+                    return FlagsPerWord * NumWords;
+                }
+        };
+
+    }
+
+    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>;
+
+}