2 files changed, 140 insertions, 0 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index eb05e46a8..45332cf95 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -97,6 +97,7 @@ add_library(common STATIC
     point.h
     precompiled_headers.h
     quaternion.h
+    range_map.h
     reader_writer_queue.h
     ring_buffer.h
     ${CMAKE_CURRENT_BINARY_DIR}/scm_rev.cpp
diff --git a/src/common/range_map.h b/src/common/range_map.h
new file mode 100644
index 000000000..993e21643
--- /dev/null
+++ b/src/common/range_map.h
@@ -0,0 +1,139 @@
+// SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <map>
+#include <type_traits>
+
+#include "common/common_types.h"
+
+namespace Common {
+
+template <typename KeyTBase, typename ValueT>
+class RangeMap {
+private:
+    using KeyT = std::conditional_t<std::is_signed_v<KeyTBase>, typename KeyTBase,
+                                    std::make_signed_t<KeyTBase>>;
+
+public:
+    explicit RangeMap(ValueT null_value_) : null_value{null_value_} {
+        container.emplace(std::numeric_limits<KeyT>::min(), null_value);
+    };
+    ~RangeMap() = default;
+
+    void Map(KeyTBase address, KeyTBase address_end, ValueT value) {
+        KeyT new_address = static_cast<KeyT>(address);
+        KeyT new_address_end = static_cast<KeyT>(address_end);
+        if (new_address < 0) {
+            new_address = 0;
+        }
+        if (new_address_end < 0) {
+            new_address_end = 0;
+        }
+        InternalMap(new_address, new_address_end, value);
+    }
+
+    void Unmap(KeyTBase address, KeyTBase address_end) {
+        Map(address, address_end, null_value);
+    }
+
+    [[nodiscard]] size_t GetContinousSizeFrom(KeyTBase address) const {
+        const KeyT new_address = static_cast<KeyT>(address);
+        if (new_address < 0) {
+            return 0;
+        }
+        return ContinousSizeInternal(new_address);
+    }
+
+    [[nodiscard]] ValueT GetValueAt(KeyT address) const {
+        const KeyT new_address = static_cast<KeyT>(address);
+        if (new_address < 0) {
+            return null_value;
+        }
+        return GetValueInternal(new_address);
+    }
+
+private:
+    using MapType = std::map<KeyT, ValueT>;
+    using IteratorType = MapType::iterator;
+    using ConstIteratorType = MapType::const_iterator;
+
+    size_t ContinousSizeInternal(KeyT address) const {
+        const auto it = GetFirstElemnentBeforeOrOn(address);
+        if (it == container.end() || it->second == null_value) {
+            return 0;
+        }
+        const auto it_end = std::next(it);
+        if (it_end == container.end()) {
+            return std::numeric_limits<KeyT>::max() - address;
+        }
+        return it_end->first - address;
+    }
+
+    ValueT GetValueInternal(KeyT address) const {
+        const auto it = GetFirstElemnentBeforeOrOn(address);
+        if (it == container.end()) {
+            return null_value;
+        }
+        return it->second;
+    }
+
+    ConstIteratorType GetFirstElemnentBeforeOrOn(KeyT address) const {
+        auto it = container.lower_bound(address);
+        if (it == container.begin()) {
+            return it;
+        }
+        if (it != container.end() && (it->first == address)) {
+            return it;
+        }
+        --it;
+        return it;
+    }
+
+    ValueT GetFirstValueWithin(KeyT address) {
+        auto it = container.lower_bound(address);
+        if (it == container.begin()) {
+            return it->second;
+        }
+        if (it == container.end()) [[unlikely]] { // this would be a bug
+            return null_value;
+        }
+        --it;
+        return it->second;
+    }
+
+    ValueT GetLastValueWithin(KeyT address) {
+        auto it = container.upper_bound(address);
+        if (it == container.end()) {
+            return null_value;
+        }
+        if (it == container.begin()) [[unlikely]] { // this would be a bug
+            return it->second;
+        }
+        --it;
+        return it->second;
+    }
+
+    void InternalMap(KeyT address, KeyT address_end, ValueT value) {
+        const bool must_add_start = GetFirstValueWithin(address) != value;
+        const ValueT last_value = GetLastValueWithin(address_end);
+        const bool must_add_end = last_value != value;
+        auto it = container.lower_bound(address);
+        const auto it_end = container.upper_bound(address_end);
+        while (it != it_end) {
+            it = container.erase(it);
+        }
+        if (must_add_start) {
+            container.emplace(address, value);
+        }
+        if (must_add_end) {
+            container.emplace(address_end, last_value);
+        }
+    }
+
+    ValueT null_value;
+    MapType container;
+};
+
+} // namespace Common