[Minor] Forgot to add a file

src/libserver/symcache/symcache_id_list.hxx

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+/*-
+ * Copyright 2022 Vsevolod Stakhov
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef RSPAMD_SYMCACHE_ID_LIST_HXX
+#define RSPAMD_SYMCACHE_ID_LIST_HXX
+#pragma once
+
+#include <cstdint>
+#include <cstring> // for memset
+#include <algorithm> // for sort
+
+#include "config.h"
+#include "libutil/mem_pool.h"
+
+namespace rspamd::symcache {
+/*
+ * This structure is optimised to store ids list:
+ * - If the first element is -1 then use dynamic part, else use static part
+ * There is no std::variant to save space
+ */
+struct id_list {
+	union {
+		std::uint32_t st[4];
+		struct {
+			std::uint32_t e; /* First element */
+			std::uint16_t len;
+			std::uint16_t allocated;
+			std::uint32_t *n;
+		} dyn;
+	} data;
+
+	id_list() = default;
+	auto reset() {
+		std::memset(&data, 0, sizeof(data));
+	}
+
+	/**
+	 * Returns ids from a compressed list, accepting a mutable reference for number of elements
+	 * @param nids output of the number of elements
+	 * @return
+	 */
+	auto get_ids(std::size_t &nids) const -> const std::uint32_t *
+	{
+		if (data.dyn.e == -1) {
+			/* Dynamic list */
+			nids = data.dyn.len;
+
+			return data.dyn.n;
+		}
+		else {
+			auto cnt = 0;
+
+			while (data.st[cnt] != 0 && cnt < G_N_ELEMENTS(data.st)) {
+				cnt++;
+			}
+
+			nids = cnt;
+
+			return data.st;
+		}
+	}
+
+	auto add_id(std::uint32_t id, rspamd_mempool_t *pool) -> void
+	{
+		if (data.st[0] == -1) {
+			/* Dynamic array */
+			if (data.dyn.len < data.dyn.allocated) {
+				/* Trivial, append + sort */
+				data.dyn.n[data.dyn.len++] = id;
+			}
+			else {
+				/* Reallocate */
+				g_assert(data.dyn.allocated <= G_MAXINT16);
+				data.dyn.allocated *= 2;
+
+				auto *new_array = rspamd_mempool_alloc_array_type(pool,
+						data.dyn.allocated, std::uint32_t);
+				memcpy(new_array, data.dyn.n, data.dyn.len * sizeof(std::uint32_t));
+				data.dyn.n = new_array;
+				data.dyn.n[data.dyn.len++] = id;
+			}
+
+			std::sort(data.dyn.n, data.dyn.n + data.dyn.len);
+		}
+		else {
+			/* Static part */
+			auto cnt = 0u;
+			while (data.st[cnt] != 0 && cnt < G_N_ELEMENTS(data.st)) {
+				cnt++;
+			}
+
+			if (cnt < G_N_ELEMENTS(data.st)) {
+				data.st[cnt] = id;
+			}
+			else {
+				/* Switch to dynamic */
+				data.dyn.allocated = G_N_ELEMENTS(data.st) * 2;
+				auto *new_array = rspamd_mempool_alloc_array_type(pool,
+						data.dyn.allocated, std::uint32_t);
+				memcpy(new_array, data.st, sizeof(data.st));
+				data.dyn.n = new_array;
+				data.dyn.e = -1; /* Marker */
+				data.dyn.len = G_N_ELEMENTS(data.st);
+
+				/* Recursively jump to dynamic branch that will handle insertion + sorting */
+				add_id(id, pool); // tail call
+			}
+		}
+	}
+
+	auto set_ids(const std::uint32_t *ids, std::size_t nids, rspamd_mempool_t *pool) -> void {
+		if (nids <= G_N_ELEMENTS(data.st)) {
+			/* Use static version */
+			reset();
+
+			for (auto i = 0; i < nids; i++) {
+				data.st[i] = ids[i];
+			}
+		}
+		else {
+			/* Need to use a separate list */
+			data.dyn.e = -1; /* Flag */
+			data.dyn.n = rspamd_mempool_alloc_array_type(pool, nids, std::uint32_t);
+			data.dyn.len = nids;
+			data.dyn.allocated = nids;
+
+			for (auto i = 0; i < nids; i++) {
+				data.dyn.n[i] = ids[i];
+			}
+
+			/* Keep sorted */
+			std::sort(data.dyn.n, data.dyn.n + data.dyn.len);
+		}
+	}
+};
+
+static_assert(std::is_trivial_v<id_list>);
+
+}
+
+#endif //RSPAMD_SYMCACHE_ID_LIST_HXX