Add to PhobosV3 memory allocators from ProjectSidero

phobos/sys/allocators/alternatives/allocatorlist.d

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+/**
+Provides a growable list of memory allocator instances.
+
+License: Boost
+Authors: Richard (Rikki) Andrew Cattermole <firstname@lastname.co.nz>
+Copyright: 2022-2024 Richard Andrew Cattermole
+*/
+module phobos.sys.allocators.alternatives.allocatorlist;
+import phobos.sys.internal.attribute : hidden;
+import phobos.sys.typecons : Ternary;
+
+private
+{
+    import phobos.sys.allocators.api;
+
+    // guarantee tha each strategy has been initialized
+    alias ALRC = AllocatorList!(RCAllocator, (RCAllocator* poolAllocator) => poolAllocator);
+}
+
+export:
+
+/**
+A simple allocator list that relies on a given allocators (as provided by the factory function) to provide its own memory.
+
+Supports isOnlyOneAllocationOfSize method on the pool allocator to allow knowing if it can free a given allocator instance.
+
+Does not use `TypeInfo`, but will be forwarded on allocation.
+*/
+struct AllocatorList(PoolAllocator, alias factory)
+{
+export:
+    static assert(__traits(hasMember, TypeOfAllocator, "deallocateAll"),
+            "Allocator allocated by factory function must have deallocateAll method.");
+    static assert(__traits(hasMember, TypeOfAllocator, "owns"),
+            "Allocator allocated by factory function must have owns method.");
+
+    /// Source for all memory, passed by pointer/ref to factory function
+    PoolAllocator poolAllocator;
+
+    ///
+    enum NeedsLocking = true;
+
+    private
+    {
+        Node* head;
+    }
+
+scope @safe @nogc nothrow:
+     ~this()
+    {
+        deallocateAll();
+    }
+
+    ///
+    bool isNull() const
+    {
+        return poolAllocator.isNull;
+    }
+
+@trusted:
+
+    ///
+    this(return scope ref AllocatorList other)
+    {
+        this.tupleof = other.tupleof;
+        other.head = null;
+        other = AllocatorList.init;
+    }
+
+    ///
+    void[] allocate(size_t size, TypeInfo ti = null)
+    {
+        Node* current = head;
+
+        while (current !is null)
+        {
+            Node* next = current.next;
+
+            void[] ret = current.allocator.allocate(size, ti);
+
+            if (ret.length >= size)
+            {
+                return ret;
+            }
+            else if (ret.length > 0)
+            {
+                current.allocator.deallocate(ret);
+            }
+
+            current = next;
+        }
+
+        expand(size);
+        assert(head !is null);
+
+        if ((current = head) !is null)
+        {
+            void[] ret = current.allocator.allocate(size, ti);
+
+            if (ret.length >= size)
+            {
+                return ret;
+            }
+            else if (ret.length > 0)
+            {
+                current.allocator.deallocate(ret);
+            }
+        }
+
+        return null;
+    }
+
+    ///
+    bool reallocate(scope ref void[] array, size_t newSize)
+    {
+        Node* current = head;
+
+        while (current !is null)
+        {
+            Node* next = current.next;
+
+            if (current.allocator.owns(array) == Ternary.yes)
+                return current.allocator.reallocate(array, newSize);
+
+            current = next;
+        }
+
+        return false;
+    }
+
+    ///
+    bool deallocate(scope void[] array)
+    {
+        Node** parent = &head;
+        Node* current = head;
+
+        while (current !is null)
+        {
+            Node* next = current.next;
+
+            if (current.allocator.owns(array) == Ternary.yes)
+            {
+                bool got = current.allocator.deallocate(array);
+
+                if (got)
+                {
+                    static if (__traits(hasMember, PoolAllocator, "isOnlyOneAllocationOfSize"))
+                    {
+                        if (current.allocator.isOnlyOneAllocationOfSize(Node.sizeof))
+                        {
+                            PoolAllocator temp = current.allocator;
+                            *parent = current.next;
+                            temp.deallocateAll();
+                        }
+                    }
+
+                    return true;
+                }
+                else
+                    return false;
+            }
+
+            parent = &current.next;
+            current = next;
+        }
+
+        return false;
+    }
+
+    ///
+    Ternary owns(scope void[] array)
+    {
+        Node* current = head;
+
+        while (current !is null)
+        {
+            Node* next = current.next;
+
+            if (current.allocator.owns(array) == Ternary.yes)
+                return Ternary.yes;
+
+            current = next;
+        }
+
+        return Ternary.no;
+    }
+
+    ///
+    bool deallocateAll()
+    {
+        Node* current = head;
+
+        while (current !is null)
+        {
+            Node* next = current.next;
+
+            auto currentAllocator = current.allocator;
+            currentAllocator.deallocateAll();
+
+            current = next;
+        }
+
+        head = null;
+        return true;
+    }
+
+    ///
+    bool empty()
+    {
+        return false;
+    }
+
+private @hidden:
+    import std.traits : isPointer, ParameterStorageClassTuple, ParameterStorageClass;
+
+    static if (isPointer!PoolAllocator || (__traits(compiles, factory!PoolAllocator)
+            && ParameterStorageClassTuple!(factory!PoolAllocator)[0] == ParameterStorageClass.ref_))
+        alias TypeOfAllocator = typeof(factory(poolAllocator));
+    else static if (__traits(compiles, typeof(factory())))
+        alias TypeOfAllocator = typeof(factory());
+    else
+        alias TypeOfAllocator = typeof(factory({
+                typeof(poolAllocator)* ret;
+                return ret;
+            }()));
+
+    static struct Node
+    {
+        TypeOfAllocator allocator;
+        Node* next;
+    }
+
+    void expand(size_t requesting = 0)
+    {
+        import std.traits : isPointer, ParameterStorageClass, ParameterStorageClassTuple;
+        import std.algorithm : moveEmplace;
+
+        TypeOfAllocator current;
+
+        static if (isPointer!PoolAllocator || (__traits(compiles, factory!PoolAllocator)
+                && ParameterStorageClassTuple!(factory!PoolAllocator)[0] == ParameterStorageClass
+                .ref_))
+            current = factory(poolAllocator);
+        else static if (__traits(compiles, typeof(factory())))
+            current = factory();
+        else
+            current = factory(&poolAllocator);
+
+        if (requesting > 0)
+            requesting += size_t.sizeof * 8;
+
+        void[] got = current.allocate(Node.sizeof + requesting);
+        if (got is null)
+            return;
+
+        if (requesting > 0)
+        {
+            current.deallocate(got);
+            got = current.allocate(Node.sizeof);
+        }
+
+        Node* currentNode = cast(Node*) got.ptr;
+
+        moveEmplace(current, currentNode.allocator);
+        currentNode.next = head;
+
+        head = currentNode;
+    }
+}
+
+///
+unittest
+{
+    import phobos.sys.allocators.mapping.malloc;
+    import phobos.sys.allocators.buffers.region;
+
+    alias AL = AllocatorList!(Region!Mallocator, () => Region!Mallocator());
+
+    AL al;
+    assert(!al.isNull);
+    assert(!al.empty);
+
+    al = AL();
+    assert(!al.isNull);
+    assert(!al.empty);
+
+    void[] got = al.allocate(1024);
+    assert(got !is null);
+    assert(got.length == 1024);
+    assert(al.owns(got) == Ternary.yes);
+    assert(al.owns(got[10 .. 20]) == Ternary.yes);
+
+    AL al2 = al;
+    al = al2;
+
+    bool success = al.reallocate(got, 2048);
+    assert(success);
+    assert(got.length == 2048);
+
+    assert(al.owns(null) == Ternary.no);
+    assert(al.owns(got) == Ternary.yes);
+    assert(al.owns(got[10 .. 20]) == Ternary.yes);
+
+    success = al.deallocate(got);
+    assert(success);
+}