1 files changed, 130 insertions, 19 deletions
diff --git a/core/templates/pooled_list.h b/core/templates/pooled_list.h
index 360fda81f8..f13156b292 100644
--- a/core/templates/pooled_list.h
+++ b/core/templates/pooled_list.h
@@ -28,16 +28,13 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#ifndef POOLED_LIST_H
-#define POOLED_LIST_H
-
-#include "core/templates/local_vector.h"
+#pragma once
 
 // Simple template to provide a pool with O(1) allocate and free.
 // The freelist could alternatively be a linked list placed within the unused elements
 // to use less memory, however a separate freelist is probably more cache friendly.
-//
-// NOTE: Take great care when using this with non POD types. The construction and destruction
+
+// NOTE : Take great care when using this with non POD types. The construction and destruction
 // is done in the LocalVector, NOT as part of the pool. So requesting a new item does not guarantee
 // a constructor is run, and free does not guarantee a destructor.
 // You should generally handle clearing
@@ -45,33 +42,60 @@
 // This is by design for fastest use in the BVH. If you want a more general pool
 // that does call constructors / destructors on request / free, this should probably be
 // a separate template.
-template <class T, bool force_trivial = false>
+
+// The zero_on_first_request feature is optional and is useful for e.g. pools of handles,
+// which may use a ref count which we want to be initialized to zero the first time a handle is created,
+// but left alone on subsequent allocations (as will typically be incremented).
+
+// Note that there is no function to compact the pool - this would
+// invalidate any existing pool IDs held externally.
+// Compaction can be done but would rely on a more complex method
+// of preferentially giving out lower IDs in the freelist first.
+
+#include "core/templates/local_vector.h"
+
+template <class T, class U = uint32_t, bool force_trivial = false, bool zero_on_first_request = false>
 class PooledList {
-	LocalVector<T, uint32_t, force_trivial> list;
-	LocalVector<uint32_t, uint32_t, true> freelist;
+	LocalVector<T, U, force_trivial> list;
+	LocalVector<U, U, true> freelist;
 
 	// not all list members are necessarily used
-	int _used_size;
+	U _used_size;
 
 public:
 	PooledList() {
 		_used_size = 0;
 	}
 
-	int estimate_memory_use() const {
-		return (list.size() * sizeof(T)) + (freelist.size() * sizeof(uint32_t));
+	// Use with care, in most cases you should make sure to
+	// free all elements first (i.e. _used_size would be zero),
+	// although it could also be used without this as an optimization
+	// in some cases.
+	void clear() {
+		list.clear();
+		freelist.clear();
+		_used_size = 0;
+	}
+
+	uint64_t estimate_memory_use() const {
+		return ((uint64_t)list.size() * sizeof(T)) + ((uint64_t)freelist.size() * sizeof(U));
 	}
 
-	const T &operator[](uint32_t p_index) const {
+	const T &operator[](U p_index) const {
 		return list[p_index];
 	}
-	T &operator[](uint32_t p_index) {
+	T &operator[](U p_index) {
 		return list[p_index];
 	}
 
-	int size() const { return _used_size; }
+	// To be explicit in a pool there is a distinction
+	// between the number of elements that are currently
+	// in use, and the number of elements that have been reserved.
+	// Using size() would be vague.
+	U used_size() const { return _used_size; }
+	U reserved_size() const { return list.size(); }
 
-	T *request(uint32_t &r_id) {
+	T *request(U &r_id) {
 		_used_size++;
 
 		if (freelist.size()) {
@@ -79,19 +103,106 @@ public:
 			int new_size = freelist.size() - 1;
 			r_id = freelist[new_size];
 			freelist.resize(new_size);
+
 			return &list[r_id];
 		}
 
 		r_id = list.size();
 		list.resize(r_id + 1);
+
+		static_assert((!zero_on_first_request) || (__is_pod(T)), "zero_on_first_request requires trivial type");
+		if (zero_on_first_request && __is_pod(T)) {
+			list[r_id] = {};
+		}
+
 		return &list[r_id];
 	}
-	void free(const uint32_t &p_id) {
+	void free(const U &p_id) {
 		// should not be on free list already
-		CRASH_COND(p_id >= list.size());
+		ERR_FAIL_UNSIGNED_INDEX(p_id, list.size());
 		freelist.push_back(p_id);
+		ERR_FAIL_COND_MSG(!_used_size, "_used_size has become out of sync, have you double freed an item?");
 		_used_size--;
 	}
 };
 
-#endif // POOLED_LIST_H
+// a pooled list which automatically keeps a list of the active members
+template <class T, class U = uint32_t, bool force_trivial = false, bool zero_on_first_request = false>
+class TrackedPooledList {
+public:
+	U pool_used_size() const { return _pool.used_size(); }
+	U pool_reserved_size() const { return _pool.reserved_size(); }
+	U active_size() const { return _active_list.size(); }
+
+	// use with care, see the earlier notes in the PooledList clear()
+	void clear() {
+		_pool.clear();
+		_active_list.clear();
+		_active_map.clear();
+	}
+
+	U get_active_id(U p_index) const {
+		return _active_list[p_index];
+	}
+
+	const T &get_active(U p_index) const {
+		return _pool[get_active_id(p_index)];
+	}
+
+	T &get_active(U p_index) {
+		return _pool[get_active_id(p_index)];
+	}
+
+	const T &operator[](U p_index) const {
+		return _pool[p_index];
+	}
+	T &operator[](U p_index) {
+		return _pool[p_index];
+	}
+
+	T *request(U &r_id) {
+		T *item = _pool.request(r_id);
+
+		// add to the active list
+		U active_list_id = _active_list.size();
+		_active_list.push_back(r_id);
+
+		// expand the active map (this should be in sync with the pool list
+		if (_pool.used_size() > _active_map.size()) {
+			_active_map.resize(_pool.used_size());
+		}
+
+		// store in the active map
+		_active_map[r_id] = active_list_id;
+
+		return item;
+	}
+
+	void free(const U &p_id) {
+		_pool.free(p_id);
+
+		// remove from the active list.
+		U list_id = _active_map[p_id];
+
+		// zero the _active map to detect bugs (only in debug?)
+		_active_map[p_id] = -1;
+
+		_active_list.remove_unordered(list_id);
+
+		// keep the replacement in sync with the correct list Id
+		if (list_id < _active_list.size()) {
+			// which pool id has been replaced in the active list
+			U replacement_id = _active_list[list_id];
+
+			// keep that replacements map up to date with the new position
+			_active_map[replacement_id] = list_id;
+		}
+	}
+
+	const LocalVector<U, U> &get_active_list() const { return _active_list; }
+
+private:
+	PooledList<T, U, force_trivial, zero_on_first_request> _pool;
+	LocalVector<U, U> _active_map;
+	LocalVector<U, U> _active_list;
+};