Rename

src/ds/seqset.h

@@ -0,0 +1,105 @@
+#pragma once
+
+#include "address.h"
+#include "defines.h"
+#include "ptrwrap.h"
+
+#include <cstdint>
+#include <type_traits>
+
+namespace snmalloc
+{
+  /**
+   * Simple sequential queue of T.
+   *
+   * Linked using the T::next field.
+   */
+  template<typename T>
+  class SeqQueue
+  {
+    static_assert(
+      std::is_same<decltype(T::next), T*>::value,
+      "T->next must be a queue pointer to T");
+    T* head{nullptr};
+    T** end{&head};
+
+  public:
+    /**
+     * Empty queue
+     */
+    constexpr SeqQueue() = default;
+
+    /**
+     * Check for empty
+     */
+    SNMALLOC_FAST_PATH bool is_empty()
+    {
+      SNMALLOC_ASSERT(end != nullptr);
+      return &head == end;
+    }
+
+    /**
+     * Remove an element from the queue
+     *
+     * Assumes queue is non-empty
+     */
+    SNMALLOC_FAST_PATH T* pop()
+    {
+      SNMALLOC_ASSERT(!this->is_empty());
+      auto result = head;
+      if (&(head->next) == end)
+        end = &head;
+      else
+        head = head->next;
+      return result;
+    }
+
+    /**
+     * Filter
+     *
+     * Removes all elements that f returns true for.
+     * If f returns true, then filter is not allowed to look at the
+     * object again, and f is responsible for its lifetime.
+     */
+    template<typename Fn>
+    SNMALLOC_FAST_PATH void filter(Fn&& f)
+    {
+      T** prev = &head;
+      // Check for empty case.
+      if (prev == end)
+        return;
+
+      while (true)
+      {
+        T* curr = *prev;
+        // Note must read curr->next before calling `f` as `f` is allowed to
+        // mutate that field.
+        T* next = curr->next;
+        if (f(curr))
+        {
+          // Remove element;
+          *prev = next;
+        }
+        else
+        {
+          // Keep element
+          prev = &(curr->next);
+        }
+
+        if (&(curr->next) == end)
+          break;
+      }
+
+      end = prev;
+    }
+
+    /**
+     * Add an element to the queue.
+     */
+    SNMALLOC_FAST_PATH void insert(T* item)
+    {
+      *end = item;
+      end = &(item->next);
+    }
+  };
+} // namespace snmalloc