1 // Copyright 2022 The Pigweed Authors
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not
4 // use this file except in compliance with the License. You may obtain a copy of
5 // the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
12 // License for the specific language governing permissions and limitations under
13 // the License.
14 #include "pw_transfer/atomic_file_transfer_handler.h"
15
16 #include <filesystem>
17 #include <system_error>
18
19 #include "pw_log/log.h"
20 #include "pw_status/status.h"
21 #include "pw_stream/std_file_stream.h"
22 #include "pw_transfer_private/filename_generator.h"
23
24 namespace pw::transfer {
25
26 namespace {
27 // Linux Error code for Cross-Device Link Error.
28 constexpr auto CROSS_DEVICE_LINK_ERROR = 18;
29
EnsureDirectoryExists(std::string_view filepath)30 pw::Status EnsureDirectoryExists(std::string_view filepath) {
31 const auto target_directory = std::filesystem::path{filepath}.parent_path();
32 return std::filesystem::exists(target_directory) ||
33 std::filesystem::create_directories(target_directory)
34 ? pw::OkStatus()
35 : pw::Status::Internal();
36 }
37
38 // Copy file and remove on succes.
39 // If the copy fails, the file `input_target` is not removed.
CopyFile(std::string_view input_target,std::string_view output_target)40 pw::Status CopyFile(std::string_view input_target,
41 std::string_view output_target) {
42 auto err = std::error_code{};
43 std::filesystem::copy(input_target,
44 output_target,
45 std::filesystem::copy_options::overwrite_existing,
46 err);
47 if (err) {
48 PW_LOG_ERROR("Error with status code: %d (%s) during copy of file %s",
49 err.value(),
50 err.message().c_str(),
51 input_target.data());
52 return pw::Status::Internal();
53 }
54 PW_LOG_INFO("Successfully copied the file.");
55 if (!std::filesystem::remove(input_target)) {
56 PW_LOG_WARN("Failed to remove tmp file %s", input_target.data());
57 }
58 return pw::OkStatus();
59 }
60
61 // Uses the same approach as unix `mv` command. First try to rename. If we get
62 // a cross-device link error, copies then deletes input_target.
RenameFile(std::string_view input_target,std::string_view output_target)63 pw::Status RenameFile(std::string_view input_target,
64 std::string_view output_target) {
65 auto err = std::error_code{};
66 std::filesystem::rename(input_target, output_target, err);
67 if (err && err.value() == CROSS_DEVICE_LINK_ERROR) {
68 PW_LOG_INFO("%s[%d] during rename of file %s. Trying Copy/Remove.",
69 err.message().c_str(),
70 err.value(),
71 input_target.data());
72 return CopyFile(input_target, output_target);
73 }
74 return err ? pw::Status::Internal() : pw::OkStatus();
75 }
76
77 } // namespace
78
PrepareRead()79 Status AtomicFileTransferHandler::PrepareRead() {
80 auto file_path = path_.c_str();
81 PW_LOG_DEBUG("Preparing read for file %s", file_path);
82 if (!std::filesystem::exists(file_path)) {
83 PW_LOG_ERROR("File does not exist, path: %s", file_path);
84 return Status::NotFound();
85 }
86 set_reader(stream_.emplace<stream::StdFileReader>(file_path));
87 return OkStatus();
88 }
89
FinalizeRead(Status)90 void AtomicFileTransferHandler::FinalizeRead(Status) {
91 std::get<stream::StdFileReader>(stream_).Close();
92 }
93
PrepareWrite()94 Status AtomicFileTransferHandler::PrepareWrite() {
95 const std::string tmp_file = GetTempFilePath(path_);
96 PW_LOG_DEBUG("Preparing write for file %s", tmp_file.c_str());
97 set_writer(stream_.emplace<stream::StdFileWriter>(tmp_file.c_str()));
98 return OkStatus();
99 }
100
FinalizeWrite(Status status)101 Status AtomicFileTransferHandler::FinalizeWrite(Status status) {
102 std::get<stream::StdFileWriter>(stream_).Close();
103 auto tmp_file = GetTempFilePath(path_);
104 if (!status.ok() || !std::filesystem::exists(tmp_file) ||
105 std::filesystem::is_empty(tmp_file)) {
106 PW_LOG_ERROR("Transfer unsuccesful, attempt to remove temp file %s",
107 tmp_file.c_str());
108 // Remove temp file if transfer fails.
109 return std::filesystem::remove(tmp_file) ? status : Status::Aborted();
110 }
111
112 const auto directory_exists_status = EnsureDirectoryExists(path_);
113 if (!directory_exists_status.ok()) {
114 std::filesystem::remove(tmp_file);
115 return directory_exists_status;
116 }
117
118 PW_LOG_DEBUG(
119 "Copying file from: %s, to: %s", tmp_file.c_str(), path_.c_str());
120 const auto rename_status = RenameFile(tmp_file, path_);
121 if (!rename_status.ok()) {
122 std::filesystem::remove(tmp_file);
123 return rename_status;
124 }
125
126 PW_LOG_INFO("File transfer was successful.");
127 return OkStatus();
128 }
129
130 } // namespace pw::transfer
131