alloc: add chunked allocator

CMakeLists.txt

@@ -242,6 +242,8 @@ list (
     alloc/aligned/foreign.hpp
     alloc/allocator.cpp
     alloc/allocator.hpp
+    alloc/chunked.cpp
+    alloc/chunked.hpp
     alloc/easy.hpp
     alloc/fallback.cpp
     alloc/fallback.hpp

alloc/chunked.cpp

@@ -0,0 +1,14 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2021, Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "chunked.hpp"
+
+using cruft::alloc::chunked;
+
+
+///////////////////////////////////////////////////////////////////////////////

alloc/chunked.hpp

@@ -0,0 +1,89 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2021, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#if 0 && __has_include(<memory_resource>)
+    #include <memory_resource>
+#else
+    #include <cstddef>
+#endif
+
+#include <vector>
+
+
+namespace std::pmr {
+    class memory_resource {
+    public:
+        memory_resource () = default;
+        memory_resource (memory_resource const&) = default;
+        memory_resource& operator= (memory_resource const&) = default;
+        virtual ~memory_resource () = default;
+
+        [[nodiscard]] void* allocate (
+            std::size_t bytes,
+            std::size_t alignment = alignof (std::max_align_t)
+        );
+
+        void deallocate(
+            void* p,
+            std::size_t bytes,
+            std::size_t alignment = alignof(std::max_align_t)
+        );
+
+        bool is_equal (memory_resource const&) const noexcept;
+
+    private:
+        virtual void *do_allocate (std::size_t bytes, std::size_t alignment) = 0;
+        virtual void do_deallocate (void *p, std::size_t bytes, std::size_t alignment) = 0;
+        virtual bool do_is_equal (memory_resource const&) const noexcept = 0;
+    };
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+namespace cruft::alloc {
+    /// An unbounded contiguous allocator that operates on chunks, similar to
+    /// a deque.
+    ///
+    /// It's useful as a means to keep unknown sized allocations in roughly
+    /// the same memory region.
+    ///
+    /// This class models std::pmr::memory_resource.
+    class chunked : public std::pmr::memory_resource {
+    public:
+        static constexpr std::size_t DEFAULT_CHUNK_SIZE = 4096;
+
+        explicit chunked (std::size_t initial_size);
+        chunked (std::size_t initial_size, std::size_t chunk_size);
+
+    private:
+        void* do_allocate (
+            std::size_t bytes,
+            std::size_t alignment = alignof (std::max_align_t)
+        ) override;
+
+        void do_deallocate (
+            void *p,
+            std::size_t bytes,
+            std::size_t alignment = alignof (std::max_align_t)
+        ) override;
+
+        bool do_is_equal (memory_resource const&) const noexcept override;
+
+        std::size_t m_chunk;
+        struct arena {
+            std::byte*  base;
+            std::size_t size;
+            std::byte*  next;
+        };
+
+        std::vector<arena> m_data;
+        int m_next;
+    };
+}