added native file logging

sharing/linux/app/BUILD

@@ -1,4 +1,5 @@
 load("@rules_cc//cc:cc_library.bzl", "cc_library")
+load("@rules_cc//cc:cc_test.bzl", "cc_test")
 load("@rules_qt//:qt.bzl", "qt_cc_binary", "qt_cc_library", "qt_resource_via_qrc")
 load("@rules_shell//shell:sh_binary.bzl", "sh_binary")
 
@@ -67,6 +68,38 @@ qt_cc_library(
     ],
 )
 
+cc_library(
+    name = "native_file_logging",
+    srcs = ["native_file_logging.cc"],
+    hdrs = ["native_file_logging.h"],
+    deps = [
+        "//sharing/linux:linux_sharing_platform",
+        "@com_google_absl//absl/base:log_severity",
+        "@com_google_absl//absl/log:globals",
+        "@com_google_absl//absl/log:initialize",
+        "@com_google_absl//absl/log:log_entry",
+        "@com_google_absl//absl/log:log_sink",
+        "@com_google_absl//absl/log:log_sink_registry",
+        "@com_google_absl//absl/strings:string_view",
+    ],
+)
+
+cc_test(
+    name = "native_file_logging_test",
+    size = "small",
+    srcs = ["native_file_logging_test.cc"],
+    deps = [
+        ":native_file_logging",
+        "//sharing/linux:linux_sharing_platform",
+        "@com_google_absl//absl/log",
+        "@com_google_absl//absl/log:globals",
+        "@com_google_absl//absl/log:initialize",
+        "@com_google_absl//absl/log:log_sink",
+        "@com_google_absl//absl/log:log_sink_registry",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 qt_cc_binary(
     name = "app",
     srcs = ["main.cc"],
@@ -76,6 +109,7 @@ qt_cc_binary(
     deps = [
         ":app_resources",
         ":backend",
+        ":native_file_logging",
         "@rules_qt//:qt_core",
         "@rules_qt//:qt_gui",
         "@rules_qt//:qt_hdrs",

sharing/linux/app/main.cc

@@ -18,6 +18,7 @@
 #include <QQmlContext>
 #include "backend.h"
 #include "qobject.h"
+#include "sharing/linux/app/native_file_logging.h"
 
 namespace {
 
@@ -113,6 +114,8 @@ void InstallTerminationCleanup(QApplication& app) {
 }  // namespace
 
 int main(int argc, char* argv[]) {
+  std::unique_ptr<nearby::sharing::linux::NativeFileLogging> native_logging =
+      nearby::sharing::linux::NativeFileLogging::Initialize();
   QApplication app(argc, argv);
   app.setApplicationName(QStringLiteral("QuickShare"));
   app.setDesktopFileName(QStringLiteral("quickshare"));

sharing/linux/app/native_file_logging.cc

@@ -0,0 +1,213 @@
+// Copyright 2026 Google LLC
+//
+// 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
+//
+//     https://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.
+
+#include "sharing/linux/app/native_file_logging.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <cstdio>
+#include <system_error>
+#include <utility>
+
+#include "absl/log/globals.h"
+#include "absl/log/initialize.h"
+#include "absl/log/log_sink_registry.h"
+#include "absl/strings/string_view.h"
+#include "sharing/linux/platform/platform_util.h"
+
+namespace nearby::sharing::linux {
+namespace {
+
+constexpr char kLogFileName[] = "quickshare.log";
+constexpr char kLockFileName[] = ".quickshare.log.lock";
+
+bool WriteAll(int fd, const char* data, size_t size) {
+  while (size > 0) {
+    const ssize_t written = write(fd, data, size);
+    if (written < 0) {
+      if (errno == EINTR) {
+        continue;
+      }
+      return false;
+    }
+    data += written;
+    size -= static_cast<size_t>(written);
+  }
+  return true;
+}
+
+void WriteToStderr(absl::string_view message) {
+  static_cast<void>(WriteAll(STDERR_FILENO, message.data(), message.size()));
+}
+
+}  // namespace
+
+std::unique_ptr<NativeFileLogSink> NativeFileLogSink::Create(
+    std::filesystem::path log_directory, size_t max_file_size, int file_count) {
+  if (max_file_size == 0 || file_count < 1) {
+    return nullptr;
+  }
+
+  std::error_code error;
+  std::filesystem::create_directories(log_directory, error);
+  if (error) {
+    return nullptr;
+  }
+  std::filesystem::permissions(log_directory, std::filesystem::perms::owner_all,
+                               std::filesystem::perm_options::replace, error);
+  if (error) {
+    return nullptr;
+  }
+
+  const std::filesystem::path lock_path = log_directory / kLockFileName;
+  const int lock_fd =
+      open(lock_path.c_str(), O_CREAT | O_RDWR | O_CLOEXEC | O_NOFOLLOW, 0600);
+  if (lock_fd < 0) {
+    return nullptr;
+  }
+  if (fchmod(lock_fd, 0600) != 0) {
+    close(lock_fd);
+    return nullptr;
+  }
+
+  const std::filesystem::path log_path = log_directory / kLogFileName;
+  const int log_fd =
+      open(log_path.c_str(),
+           O_CREAT | O_WRONLY | O_APPEND | O_CLOEXEC | O_NOFOLLOW, 0600);
+  if (log_fd < 0 || fchmod(log_fd, 0600) != 0) {
+    if (log_fd >= 0) {
+      close(log_fd);
+    }
+    close(lock_fd);
+    return nullptr;
+  }
+  close(log_fd);
+
+  return std::unique_ptr<NativeFileLogSink>(new NativeFileLogSink(
+      std::move(log_directory), lock_fd, max_file_size, file_count));
+}
+
+NativeFileLogSink::NativeFileLogSink(std::filesystem::path log_directory,
+                                     int lock_fd, size_t max_file_size,
+                                     int file_count)
+    : log_path_(std::move(log_directory) / kLogFileName),
+      lock_fd_(lock_fd),
+      max_file_size_(max_file_size),
+      file_count_(file_count) {}
+
+NativeFileLogSink::~NativeFileLogSink() {
+  close(lock_fd_);
+}
+
+void NativeFileLogSink::Send(const absl::LogEntry& entry) {
+  const absl::string_view message =
+      entry.text_message_with_prefix_and_newline();
+  const bool flush = entry.log_severity() >= absl::LogSeverity::kError;
+
+  std::lock_guard<std::mutex> lock(mutex_);
+  if (flock(lock_fd_, LOCK_EX) != 0) {
+    WriteFallback(message.data(), message.size());
+    return;
+  }
+
+  const bool success = RotateIfNeeded(message.size()) &&
+                       WriteRecord(message.data(), message.size(), flush);
+  static_cast<void>(flock(lock_fd_, LOCK_UN));
+  if (!success) {
+    WriteFallback(message.data(), message.size());
+  }
+}
+
+bool NativeFileLogSink::RotateIfNeeded(size_t incoming_size) {
+  struct stat status{};
+  if (stat(log_path_.c_str(), &status) != 0) {
+    return errno == ENOENT;
+  }
+  const size_t current_size =
+      status.st_size > 0 ? static_cast<size_t>(status.st_size) : 0;
+  if (current_size == 0 || (incoming_size <= max_file_size_ &&
+                            current_size <= max_file_size_ - incoming_size)) {
+    return true;
+  }
+
+  for (int index = file_count_ - 1; index >= 1; --index) {
+    const std::filesystem::path destination =
+        log_path_.string() + "." + std::to_string(index);
+    const std::filesystem::path source =
+        index == 1 ? log_path_
+                   : std::filesystem::path(log_path_.string() + "." +
+                                           std::to_string(index - 1));
+    if (rename(source.c_str(), destination.c_str()) != 0 && errno != ENOENT) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool NativeFileLogSink::WriteRecord(const char* data, size_t size, bool flush) {
+  const int fd =
+      open(log_path_.c_str(),
+           O_CREAT | O_WRONLY | O_APPEND | O_CLOEXEC | O_NOFOLLOW, 0600);
+  if (fd < 0) {
+    return false;
+  }
+
+  bool success = fchmod(fd, 0600) == 0 && WriteAll(fd, data, size);
+  if (success && flush) {
+    success = fsync(fd) == 0;
+  }
+  if (close(fd) != 0) {
+    success = false;
+  }
+  return success;
+}
+
+void NativeFileLogSink::WriteFallback(const char* data, size_t size) {
+  WriteToStderr(absl::string_view(data, size));
+}
+
+std::unique_ptr<NativeFileLogging> NativeFileLogging::Initialize() {
+  std::unique_ptr<NativeFileLogSink> sink =
+      NativeFileLogSink::Create(internal::GetQuickShareLogPath().ToString());
+  absl::InitializeLog();
+  if (sink == nullptr) {
+    WriteToStderr(
+        "QuickShare: unable to initialize file logging; using "
+        "stderr.\n");
+    return nullptr;
+  }
+
+  absl::AddLogSink(sink.get());
+  const absl::LogSeverityAtLeast previous_threshold = absl::StderrThreshold();
+  absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfinity);
+  return std::unique_ptr<NativeFileLogging>(
+      new NativeFileLogging(std::move(sink), previous_threshold));
+}
+
+NativeFileLogging::NativeFileLogging(
+    std::unique_ptr<NativeFileLogSink> sink,
+    absl::LogSeverityAtLeast previous_stderr_threshold)
+    : sink_(std::move(sink)),
+      previous_stderr_threshold_(previous_stderr_threshold) {}
+
+NativeFileLogging::~NativeFileLogging() {
+  absl::SetStderrThreshold(previous_stderr_threshold_);
+  absl::RemoveLogSink(sink_.get());
+}
+
+}  // namespace nearby::sharing::linux

sharing/linux/app/native_file_logging.h

@@ -0,0 +1,82 @@
+// Copyright 2026 Google LLC
+//
+// 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
+//
+//     https://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 SHARING_LINUX_APP_NATIVE_FILE_LOGGING_H_
+#define SHARING_LINUX_APP_NATIVE_FILE_LOGGING_H_
+
+#include <cstddef>
+#include <filesystem>
+#include <memory>
+#include <mutex>
+
+#include "absl/base/log_severity.h"
+#include "absl/log/log_entry.h"
+#include "absl/log/log_sink.h"
+
+namespace nearby::sharing::linux {
+
+class NativeFileLogSink final : public absl::LogSink {
+ public:
+  static constexpr size_t kDefaultMaxFileSize = 10 * 1024 * 1024;
+  static constexpr int kDefaultFileCount = 5;
+
+  static std::unique_ptr<NativeFileLogSink> Create(
+      std::filesystem::path log_directory,
+      size_t max_file_size = kDefaultMaxFileSize,
+      int file_count = kDefaultFileCount);
+
+  NativeFileLogSink(const NativeFileLogSink&) = delete;
+  NativeFileLogSink& operator=(const NativeFileLogSink&) = delete;
+  ~NativeFileLogSink() override;
+
+  void Send(const absl::LogEntry& entry) override;
+
+  const std::filesystem::path& log_path() const { return log_path_; }
+
+ private:
+  NativeFileLogSink(std::filesystem::path log_directory, int lock_fd,
+                    size_t max_file_size, int file_count);
+
+  bool RotateIfNeeded(size_t incoming_size);
+  bool WriteRecord(const char* data, size_t size, bool flush);
+  void WriteFallback(const char* data, size_t size);
+
+  std::filesystem::path log_path_;
+  int lock_fd_;
+  size_t max_file_size_;
+  int file_count_;
+  std::mutex mutex_;
+};
+
+// Owns the process-wide Abseil sink registration. Initialize() must be called
+// exactly once, before any application components start logging.
+class NativeFileLogging final {
+ public:
+  static std::unique_ptr<NativeFileLogging> Initialize();
+
+  NativeFileLogging(const NativeFileLogging&) = delete;
+  NativeFileLogging& operator=(const NativeFileLogging&) = delete;
+  ~NativeFileLogging();
+
+ private:
+  NativeFileLogging(std::unique_ptr<NativeFileLogSink> sink,
+                    absl::LogSeverityAtLeast previous_stderr_threshold);
+
+  std::unique_ptr<NativeFileLogSink> sink_;
+  absl::LogSeverityAtLeast previous_stderr_threshold_;
+};
+
+}  // namespace nearby::sharing::linux
+
+#endif  // SHARING_LINUX_APP_NATIVE_FILE_LOGGING_H_

sharing/linux/app/native_file_logging_test.cc

@@ -0,0 +1,265 @@
+// Copyright 2026 Google LLC
+//
+// 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
+//
+//     https://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.
+
+#include "sharing/linux/app/native_file_logging.h"
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <mutex>
+#include <optional>
+#include <sstream>
+#include <string>
+#include <thread>
+#include <utility>
+#include <vector>
+
+#include "absl/log/globals.h"
+#include "absl/log/initialize.h"
+#include "absl/log/log.h"
+#include "absl/log/log_sink.h"
+#include "absl/log/log_sink_registry.h"
+#include "gtest/gtest.h"
+#include "sharing/linux/platform/platform_util.h"
+
+namespace nearby::sharing::linux {
+namespace {
+
+class TemporaryDirectory {
+ public:
+  TemporaryDirectory() {
+    std::string path =
+        (std::filesystem::temp_directory_path() /
+         ("quickshare-logging-test-" + std::to_string(getpid()) + "-XXXXXX"))
+            .string();
+    path.push_back('\0');
+    char* created = mkdtemp(path.data());
+    EXPECT_NE(created, nullptr);
+    if (created != nullptr) {
+      path_ = created;
+    }
+  }
+
+  ~TemporaryDirectory() {
+    std::error_code error;
+    std::filesystem::remove_all(path_, error);
+  }
+
+  const std::filesystem::path& path() const { return path_; }
+
+ private:
+  std::filesystem::path path_;
+};
+
+class ScopedEnvironmentVariable {
+ public:
+  ScopedEnvironmentVariable(const char* name, std::optional<std::string> value)
+      : name_(name) {
+    const char* old_value = std::getenv(name);
+    if (old_value != nullptr) {
+      old_value_ = old_value;
+    }
+    if (value.has_value()) {
+      setenv(name, value->c_str(), 1);
+    } else {
+      unsetenv(name);
+    }
+  }
+
+  ~ScopedEnvironmentVariable() {
+    if (old_value_.has_value()) {
+      setenv(name_.c_str(), old_value_->c_str(), 1);
+    } else {
+      unsetenv(name_.c_str());
+    }
+  }
+
+ private:
+  std::string name_;
+  std::optional<std::string> old_value_;
+};
+
+class CaptureSink final : public absl::LogSink {
+ public:
+  void Send(const absl::LogEntry& entry) override {
+    std::lock_guard<std::mutex> lock(mutex_);
+    records_.emplace_back(entry.text_message_with_prefix_and_newline());
+  }
+
+  std::vector<std::string> records() {
+    std::lock_guard<std::mutex> lock(mutex_);
+    return records_;
+  }
+
+ private:
+  std::mutex mutex_;
+  std::vector<std::string> records_;
+};
+
+void EnsureAbslLoggingInitialized() {
+  static const bool initialized = [] {
+    absl::InitializeLog();
+    return true;
+  }();
+  static_cast<void>(initialized);
+}
+
+std::string ReadFile(const std::filesystem::path& path) {
+  std::ifstream stream(path, std::ios::binary);
+  std::ostringstream contents;
+  contents << stream.rdbuf();
+  return contents.str();
+}
+
+int PermissionBits(const std::filesystem::path& path) {
+  struct stat status{};
+  EXPECT_EQ(stat(path.c_str(), &status), 0);
+  return status.st_mode & 0777;
+}
+
+TEST(NativeFileLogSinkTest, PreservesOriginalAbseilRecord) {
+  EnsureAbslLoggingInitialized();
+  TemporaryDirectory temporary_directory;
+  auto sink = NativeFileLogSink::Create(temporary_directory.path());
+  ASSERT_NE(sink, nullptr);
+  CaptureSink capture;
+  absl::ScopedStderrThreshold suppress_stderr(
+      absl::LogSeverityAtLeast::kInfinity);
+  absl::AddLogSink(sink.get());
+  absl::AddLogSink(&capture);
+
+  LOG(INFO) << "native-record-sentinel";
+
+  absl::RemoveLogSink(&capture);
+  absl::RemoveLogSink(sink.get());
+  const std::vector<std::string> records = capture.records();
+  ASSERT_EQ(records.size(), size_t{1});
+  EXPECT_EQ(ReadFile(sink->log_path()), records.front());
+}
+
+TEST(NativeFileLogSinkTest, RotatesAndRetainsFiveFiles) {
+  EnsureAbslLoggingInitialized();
+  TemporaryDirectory temporary_directory;
+  auto sink = NativeFileLogSink::Create(temporary_directory.path(), 256, 5);
+  ASSERT_NE(sink, nullptr);
+  absl::ScopedStderrThreshold suppress_stderr(
+      absl::LogSeverityAtLeast::kInfinity);
+  absl::AddLogSink(sink.get());
+
+  for (int index = 0; index < 8; ++index) {
+    LOG(INFO) << "rotation-record-" << index << "-" << std::string(180, 'x');
+  }
+
+  absl::RemoveLogSink(sink.get());
+  EXPECT_TRUE(std::filesystem::exists(sink->log_path()));
+  for (int index = 1; index <= 4; ++index) {
+    EXPECT_TRUE(std::filesystem::exists(sink->log_path().string() + "." +
+                                        std::to_string(index)));
+  }
+  EXPECT_FALSE(std::filesystem::exists(sink->log_path().string() + ".5"));
+}
+
+TEST(NativeFileLogSinkTest, SerializesConcurrentRecords) {
+  EnsureAbslLoggingInitialized();
+  TemporaryDirectory temporary_directory;
+  auto sink = NativeFileLogSink::Create(temporary_directory.path());
+  ASSERT_NE(sink, nullptr);
+  absl::ScopedStderrThreshold suppress_stderr(
+      absl::LogSeverityAtLeast::kInfinity);
+  absl::AddLogSink(sink.get());
+
+  std::vector<std::thread> threads;
+  for (int thread = 0; thread < 4; ++thread) {
+    threads.emplace_back([thread] {
+      for (int record = 0; record < 20; ++record) {
+        LOG(INFO) << "concurrent-record-" << thread << "-" << record;
+      }
+    });
+  }
+  for (std::thread& thread : threads) {
+    thread.join();
+  }
+
+  absl::RemoveLogSink(sink.get());
+  const std::string contents = ReadFile(sink->log_path());
+  size_t record_count = 0;
+  size_t position = 0;
+  while ((position = contents.find("concurrent-record-", position)) !=
+         std::string::npos) {
+    ++record_count;
+    position += 18;
+  }
+  EXPECT_EQ(record_count, size_t{80});
+}
+
+TEST(NativeFileLogSinkTest, UsesPrivatePermissions) {
+  TemporaryDirectory temporary_directory;
+  const std::filesystem::path log_directory =
+      temporary_directory.path() / "nested" / "logs";
+  auto sink = NativeFileLogSink::Create(log_directory);
+  ASSERT_NE(sink, nullptr);
+
+  EXPECT_EQ(PermissionBits(log_directory), 0700);
+  EXPECT_EQ(PermissionBits(sink->log_path()), 0600);
+  EXPECT_EQ(PermissionBits(log_directory / ".quickshare.log.lock"), 0600);
+}
+
+TEST(NativeFileLogSinkTest, RejectsUnavailableDirectory) {
+  TemporaryDirectory temporary_directory;
+  const std::filesystem::path regular_file =
+      temporary_directory.path() / "not-a-directory";
+  {
+    std::ofstream stream(regular_file);
+    stream << "content";
+  }
+
+  EXPECT_EQ(NativeFileLogSink::Create(regular_file), nullptr);
+}
+
+TEST(LogPathTest, UsesAbsoluteXdgStateHome) {
+  TemporaryDirectory temporary_directory;
+  ScopedEnvironmentVariable state_home("XDG_STATE_HOME",
+                                       temporary_directory.path().string());
+
+  EXPECT_EQ(internal::GetQuickShareLogPath().ToString(),
+            (temporary_directory.path() / "quickshare" / "logs").string());
+}
+
+TEST(LogPathTest, FallsBackToHomeForRelativeXdgStateHome) {
+  TemporaryDirectory temporary_directory;
+  ScopedEnvironmentVariable home("HOME", temporary_directory.path().string());
+  ScopedEnvironmentVariable state_home("XDG_STATE_HOME", "relative/path");
+
+  EXPECT_EQ(
+      internal::GetQuickShareLogPath().ToString(),
+      (temporary_directory.path() / ".local" / "state" / "quickshare" / "logs")
+          .string());
+}
+
+TEST(LogPathTest, FallsBackToHomeWhenXdgStateHomeIsMissing) {
+  TemporaryDirectory temporary_directory;
+  ScopedEnvironmentVariable home("HOME", temporary_directory.path().string());
+  ScopedEnvironmentVariable state_home("XDG_STATE_HOME", std::nullopt);
+
+  EXPECT_EQ(
+      internal::GetQuickShareLogPath().ToString(),
+      (temporary_directory.path() / ".local" / "state" / "quickshare" / "logs")
+          .string());
+}
+
+}  // namespace
+}  // namespace nearby::sharing::linux