add function to truncate over-sized files part of a torrent

CMakeLists.txt

@@ -139,6 +139,7 @@ set(libtorrent_include_files
 	torrent_peer_allocator.hpp
 	torrent_status.hpp
 	tracker_manager.hpp
+	truncate.hpp
 	udp_socket.hpp
 	udp_tracker_connection.hpp
 	union_endpoint.hpp
@@ -402,6 +403,7 @@ set(sources
 	torrent_peer_allocator.cpp
 	torrent_status.cpp
 	tracker_manager.cpp
+	truncate.cpp
 	udp_socket.cpp
 	udp_tracker_connection.cpp
 	upnp.cpp

ChangeLog

@@ -1,3 +1,4 @@
+	* add function to truncate over-sized files part of a torrent
 	* fix directory creation on windows shared folders
 	* add flag to make add_files() not record file attributes
 	* deprecate (unused) allow_partial_disk_writes settings

Jamfile

@@ -822,6 +822,7 @@ SOURCES =
 	posix_part_file
 	posix_storage
 	ssl
+	truncate
 
 # -- extensions --
 	ut_pex

Makefile

@@ -402,6 +402,7 @@ SOURCES = \
   torrent_peer_allocator.cpp      \
   torrent_status.cpp              \
   tracker_manager.cpp             \
+  truncate.cpp                    \
   udp_socket.cpp                  \
   udp_tracker_connection.cpp      \
   upnp.cpp                        \
@@ -544,6 +545,7 @@ HEADERS = \
   torrent_peer_allocator.hpp   \
   torrent_status.hpp           \
   tracker_manager.hpp          \
+  truncate.hpp                 \
   udp_socket.hpp               \
   udp_tracker_connection.hpp   \
   union_endpoint.hpp           \
@@ -915,6 +917,7 @@ TEST_SOURCES = \
   test_torrent_info.cpp \
   test_torrent_list.cpp \
   test_tracker.cpp \
+  test_truncate.cpp \
   test_transfer.cpp \
   test_upnp.cpp \
   test_url_seed.cpp \

include/libtorrent/truncate.hpp

@@ -0,0 +1,48 @@
+/*
+
+Copyright (c) 2022, 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_TRUNCATE_HPP_INCLUDED
+#define TORRENT_TRUNCATE_HPP_INCLUDED
+
+#include "libtorrent/fwd.hpp"
+#include "libtorrent/error_code.hpp"
+#include <string>
+
+namespace libtorrent {
+
+// Truncates files larger than specified in the file_storage, saved under
+// the specified save_path.
+TORRENT_EXPORT void truncate_files(file_storage const& fs, std::string const& save_path, storage_error& ec);
+
+}
+
+#endif

src/truncate.cpp

@@ -0,0 +1,177 @@
+/*
+
+Copyright (c) 2022, 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.
+
+*/
+
+#include "libtorrent/truncate.hpp"
+#include "libtorrent/file_storage.hpp"
+#include "libtorrent/aux_/path.hpp"
+#include "libtorrent/operations.hpp"
+
+#ifdef TORRENT_WINDOWS
+#include "libtorrent/aux_/windows.hpp"
+#else
+#include <sys/stat.h>
+#endif
+
+namespace libtorrent {
+
+#ifdef TORRENT_WINDOWS
+
+void truncate_files(file_storage const& fs, std::string const& save_path, storage_error& ec)
+{
+	for (auto i : fs.file_range())
+	{
+		if (fs.pad_file_at(i)) continue;
+		auto const fn = fs.file_path(i, save_path);
+		native_path_string const file_path = convert_to_native_path_string(fn);
+#ifdef TORRENT_WINRT
+		HANDLE handle = CreateFile2(file_path.c_str()
+			, GENERIC_WRITE | GENERIC_READ
+			, FILE_SHARE_READ | FILE_SHARE_WRITE
+			, OPEN_EXISTING
+			, nullptr);
+#else
+		HANDLE handle = CreateFileW(file_path.c_str()
+			, GENERIC_WRITE | GENERIC_READ
+			, FILE_SHARE_READ | FILE_SHARE_WRITE
+			, nullptr
+			, OPEN_EXISTING
+			, 0
+			, nullptr);
+#endif
+		if (handle == INVALID_HANDLE_VALUE)
+		{
+			auto const error = ::GetLastError();
+			if (error != ERROR_FILE_NOT_FOUND)
+			{
+				ec.ec.assign(error, system_category());
+				ec.file(i);
+				ec.operation = operation_t::file_open;
+				return;
+			}
+			continue;
+		}
+
+		LARGE_INTEGER file_size;
+		if (GetFileSizeEx(handle, &file_size) == FALSE)
+		{
+			ec.ec.assign(::GetLastError(), system_category());
+			ec.file(i);
+			ec.operation = operation_t::file_stat;
+			::CloseHandle(handle);
+			return;
+		}
+
+		if (file_size.QuadPart < fs.file_size(i))
+		{
+			::CloseHandle(handle);
+			continue;
+		}
+
+		LARGE_INTEGER sz;
+		sz.QuadPart = fs.file_size(i);
+		if (SetFilePointerEx(handle, sz, nullptr, FILE_BEGIN) == FALSE)
+		{
+			ec.ec.assign(::GetLastError(), system_category());
+			ec.file(i);
+			ec.operation = operation_t::file_seek;
+			::CloseHandle(handle);
+			return;
+		}
+
+		if (::SetEndOfFile(handle) == FALSE)
+		{
+			ec.ec.assign(::GetLastError(), system_category());
+			ec.file(i);
+			ec.operation = operation_t::file_truncate;
+			::CloseHandle(handle);
+			return;
+		}
+		::CloseHandle(handle);
+	}
+}
+
+#else
+
+void truncate_files(file_storage const& fs, std::string const& save_path, storage_error& ec)
+{
+	for (auto i : fs.file_range())
+	{
+		if (fs.pad_file_at(i)) continue;
+		auto const fn = fs.file_path(i, save_path);
+		native_path_string const file_path = convert_to_native_path_string(fn);
+		int const fd = ::open(file_path.c_str(), O_RDWR);
+
+		if (fd < 0)
+		{
+			int const error = errno;
+			if (error != ENOENT)
+			{
+				ec.ec.assign(error, generic_category());
+				ec.file(i);
+				ec.operation = operation_t::file_open;
+				return;
+			}
+			continue;
+		}
+
+		struct ::stat st;
+		if (::fstat(fd, &st) != 0)
+		{
+			ec.ec.assign(errno, system_category());
+			ec.file(i);
+			ec.operation = operation_t::file_stat;
+			::close(fd);
+			return;
+		}
+
+		if (st.st_size < fs.file_size(i))
+		{
+			::close(fd);
+			continue;
+		}
+
+		if (::ftruncate(fd, static_cast<off_t>(fs.file_size(i))) < 0)
+		{
+			ec.ec.assign(errno, system_category());
+			ec.file(i);
+			ec.operation = operation_t::file_truncate;
+			::close(fd);
+			return;
+		}
+
+		::close(fd);
+	}
+}
+
+#endif
+
+}

test/Jamfile

@@ -200,6 +200,7 @@ run test_hash_picker.cpp ;
 run test_torrent.cpp ;
 run test_remap_files.cpp ;
 run test_similar_torrent.cpp ;
+run test_truncate.cpp ;
 
 # turn these tests into simulations
 run test_resume.cpp ;
@@ -314,4 +315,5 @@ alias deterministic-tests :
 	test_xml
 	test_store_buffer
 	test_similar_torrent
+	test_truncate
 	;