factor out storage index free list from mmap_disk_io and posix_disk_io

CMakeLists.txt

@@ -257,6 +257,7 @@ set(libtorrent_aux_include_files
 	session_udp_sockets.hpp
 	set_socket_buffer.hpp
 	socket_type.hpp
+	storage_free_list.hpp
 	storage_utils.hpp
 	string_ptr.hpp
 	strview_less.hpp

Makefile

@@ -635,6 +635,7 @@ HEADERS = \
   aux_/set_socket_buffer.hpp        \
   aux_/sha512.hpp                   \
   aux_/socket_type.hpp              \
+  aux_/storage_free_list.hpp        \
   aux_/storage_utils.hpp            \
   aux_/store_buffer.hpp             \
   aux_/string_ptr.hpp               \

include/libtorrent/aux_/storage_free_list.hpp

@@ -0,0 +1,71 @@
+/*
+
+Copyright (c) 2021, Arvid Norberg
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in
+      the documentation and/or other materials provided with the distribution.
+    * Neither the name of the author nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+*/
+
+#ifndef TORRENT_STORAGE_FREE_LIST_HPP_INCLUDE
+#define TORRENT_STORAGE_FREE_LIST_HPP_INCLUDE
+
+#include <vector>
+#include "libtorrent/storage_defs.hpp"
+
+namespace libtorrent {
+namespace aux {
+
+	struct storage_free_list
+	{
+		// if we don't already have any free slots, use next
+		storage_index_t new_index(storage_index_t const next)
+		{
+			// make sure we can remove this torrent without causing a memory
+			// allocation, by triggering the allocation now instead
+			m_free_slots.reserve(static_cast<std::uint32_t>(next) + 1);
+			return m_free_slots.empty() ? next : pop();
+		}
+
+		void add(storage_index_t const i) { m_free_slots.push_back(i); }
+
+	private:
+
+		storage_index_t pop()
+		{
+			TORRENT_ASSERT(!m_free_slots.empty());
+			storage_index_t const ret = m_free_slots.back();
+			m_free_slots.pop_back();
+			return ret;
+		}
+
+	private:
+		std::vector<storage_index_t> m_free_slots;
+	};
+}
+}
+#endif
+

src/mmap_disk_io.cpp

@@ -58,11 +58,11 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/aux_/alloca.hpp"
 #include "libtorrent/aux_/array.hpp"
 #include "libtorrent/add_torrent_params.hpp"
-#include "libtorrent/aux_/merkle.hpp"
 #include "libtorrent/aux_/numeric_cast.hpp"
 #include "libtorrent/settings_pack.hpp"
 #include "libtorrent/aux_/file_view_pool.hpp"
 #include "libtorrent/aux_/scope_end.hpp"
+#include "libtorrent/aux_/storage_free_list.hpp"
 
 #ifdef _WIN32
 #include "libtorrent/aux_/windows.hpp"
@@ -139,14 +139,6 @@ namespace {
 		if (!(j->flags & disk_interface::sequential_access)) ret |= aux::open_mode::random_access;
 		return ret;
 	}
-
-	storage_index_t pop(std::vector<storage_index_t>& q)
-	{
-		TORRENT_ASSERT(!q.empty());
-		storage_index_t const ret = q.back();
-		q.pop_back();
-		return ret;
-	}
 } // anonymous namespace
 
 using jobqueue_t = tailqueue<aux::disk_io_job>;
@@ -365,7 +357,7 @@ struct TORRENT_EXTRA_EXPORT mmap_disk_io final
 	aux::vector<std::shared_ptr<mmap_storage>, storage_index_t> m_torrents;
 
 	// indices into m_torrents to empty slots
-	std::vector<storage_index_t> m_free_slots;
+	aux::storage_free_list m_free_slots;
 
 	std::atomic_flag m_jobs_aborted = ATOMIC_FLAG_INIT;
 
@@ -406,27 +398,20 @@ TORRENT_EXPORT std::unique_ptr<disk_interface> mmap_disk_io_constructor(
 	{
 		TORRENT_ASSERT(params.files.is_valid());
 
-		storage_index_t const idx = m_free_slots.empty()
-			? m_torrents.end_index()
-			: pop(m_free_slots);
+		storage_index_t const idx = m_free_slots.new_index(m_torrents.end_index());
 		auto storage = std::make_shared<mmap_storage>(params, m_file_pool);
 		storage->set_storage_index(idx);
 		storage->set_owner(owner);
 		if (idx == m_torrents.end_index())
-		{
-			// make sure there's always space in here to add another free slot.
-			// stopping a torrent should never fail because it needs to allocate memory
-			m_free_slots.reserve(m_torrents.size() + 1);
 			m_torrents.emplace_back(std::move(storage));
-		}
 		else m_torrents[idx] = std::move(storage);
 		return storage_holder(idx, *this);
 	}
 
 	void mmap_disk_io::remove_torrent(storage_index_t const idx)
 	{
 		m_torrents[idx].reset();
-		m_free_slots.push_back(idx);
+		m_free_slots.add(idx);
 	}
 
 #if TORRENT_USE_ASSERTS

src/posix_disk_io.cpp

@@ -46,22 +46,14 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/file_storage.hpp"
 #include "libtorrent/hasher.hpp"
 #include "libtorrent/add_torrent_params.hpp"
-#include "libtorrent/aux_/merkle.hpp"
+#include "libtorrent/aux_/storage_free_list.hpp"
 
 #include <vector>
 
 namespace libtorrent {
 
 namespace {
 
-	storage_index_t pop(std::vector<storage_index_t>& q)
-	{
-		TORRENT_ASSERT(!q.empty());
-		storage_index_t const ret = q.back();
-		q.pop_back();
-		return ret;
-	}
-
 	using aux::posix_storage;
 
 } // anonymous namespace
@@ -89,10 +81,7 @@ namespace {
 		{
 			// make sure we can remove this torrent without causing a memory
 			// allocation, by causing the allocation now instead
-			m_free_slots.reserve(m_torrents.size() + 1);
-			storage_index_t const idx = m_free_slots.empty()
-				? m_torrents.end_index()
-				: pop(m_free_slots);
+			storage_index_t const idx = m_free_slots.new_index(m_torrents.end_index());
 			auto storage = std::make_unique<posix_storage>(params);
 			if (idx == m_torrents.end_index()) m_torrents.emplace_back(std::move(storage));
 			else m_torrents[idx] = std::move(storage);
@@ -102,7 +91,7 @@ namespace {
 		void remove_torrent(storage_index_t const idx) override
 		{
 			m_torrents[idx].reset();
-			m_free_slots.push_back(idx);
+			m_free_slots.add(idx);
 		}
 
 		void abort(bool) override {}
@@ -398,7 +387,7 @@ namespace {
 		aux::vector<std::unique_ptr<posix_storage>, storage_index_t> m_torrents;
 
 		// slots that are unused in the m_torrents vector
-		std::vector<storage_index_t> m_free_slots;
+		aux::storage_free_list m_free_slots;
 
 		settings_interface const& m_settings;