1 files changed, 59 insertions, 0 deletions
diff --git a/src/util/pool.h b/src/util/pool.h
new file mode 100644
index 0000000..544ece6
--- /dev/null
+++ b/src/util/pool.h
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** \file Pool
+ * Block allocator optimised for many allocations that are freed all at once.
+ */
+#ifndef INKSCAPE_UTIL_POOL_H
+#define INKSCAPE_UTIL_POOL_H
+
+#include <memory>
+#include <vector>
+#include <utility>
+#include <cstddef>
+
+namespace Inkscape {
+namespace Util {
+
+/**
+ * A Pool is a block allocator with the following characteristics:
+ *
+ *   - When a block cannot be allocated from the current buffer, a new 50% larger buffer is requested.
+ *   - When all blocks are freed, the largest buffer is retained.
+ *
+ * The only difference from std::pmr::monotonic_buffer_resource is the second point.
+ * Like std::pmr::monotonic_buffer_resource, it is also not thread-safe.
+ */
+class Pool final
+{
+public:
+    Pool() = default;
+    Pool(Pool const &) = delete;
+    Pool &operator=(Pool const &) = delete;
+    Pool(Pool &&other) noexcept { movefrom(other); }
+    Pool &operator=(Pool &&other) noexcept { movefrom(other); return *this; }
+
+    /// Ensure that the next buffer requested has at least the specified size.
+    void reserve(std::size_t size) { nextsize = std::max(nextsize, size); }
+
+    /// Allocate a block of the given size and alignment.
+    std::byte *allocate(std::size_t size, std::size_t alignment);
+
+    /// Convenience function: allocate a block of size and aligment for T.
+    template<typename T>
+    T *allocate() { return reinterpret_cast<T*>(allocate(sizeof(T), alignof(T))); }
+
+    /// Free all previous allocations, retaining the largest existing buffer for re-use.
+    void free_all() noexcept;
+
+private:
+    std::vector<std::unique_ptr<std::byte[]>> buffers;
+    std::byte *cur = nullptr, *end = nullptr;
+    std::size_t cursize = 0, nextsize = 2;
+
+    void movefrom(Pool &other) noexcept;
+    void resetblock() noexcept;
+};
+
+} // namespace Util
+} // namespace Inkscape
+
+#endif // INKSCAPE_UTIL_POOL_H