Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

common/log.h

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2022 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
+ *
+ *      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 COMMON_LOG_H_
+#define COMMON_LOG_H_
+
+#include <memory>
+
+#include "absl/strings/str_format.h"
+#include "absl/synchronization/mutex.h"
+#include "common/clock.h"
+
+namespace cdc_ft {
+
+enum class LogLevel { kVerbose, kDebug, kInfo, kWarning, kError };
+
+// Note: Bazel always uses forward slashes for paths.
+#define __FILENAME__ \
+  (strrchr(__FILE__, '/') ? strrchr(__FILE__, '/') + 1 : __FILE__)
+
+#define LOG_VERBOSE(...)                                                \
+  ::cdc_ft::Log::SafePrintf(::cdc_ft::LogLevel::kVerbose, __FILENAME__, \
+                            __LINE__, __func__, __VA_ARGS__);
+#define LOG_DEBUG(...)                                                \
+  ::cdc_ft::Log::SafePrintf(::cdc_ft::LogLevel::kDebug, __FILENAME__, \
+                            __LINE__, __func__, __VA_ARGS__);
+#define LOG_INFO(...)                                                          \
+  ::cdc_ft::Log::SafePrintf(::cdc_ft::LogLevel::kInfo, __FILENAME__, __LINE__, \
+                            __func__, __VA_ARGS__);
+#define LOG_WARNING(...)                                                \
+  ::cdc_ft::Log::SafePrintf(::cdc_ft::LogLevel::kWarning, __FILENAME__, \
+                            __LINE__, __func__, __VA_ARGS__);
+#define LOG_ERROR(...)                                                \
+  ::cdc_ft::Log::SafePrintf(::cdc_ft::LogLevel::kError, __FILENAME__, \
+                            __LINE__, __func__, __VA_ARGS__);
+#define LOG_LEVEL(level, ...)                                        \
+  ::cdc_ft::Log::SafePrintf(level, __FILENAME__, __LINE__, __func__, \
+                            __VA_ARGS__);
+
+class Log {
+ public:
+  // Initializes the Log singleton. Should be called in the beginning.
+  static void Initialize(std::unique_ptr<Log> log);
+
+  // Deletes the Log singleton. Must be called in the end.
+  static void Shutdown();
+
+  // Returns the global log instance.
+  static Log* Instance();
+
+  template <typename... Args>
+  static void SafePrintf(LogLevel level, const char* file, int line,
+                         const char* func,
+                         const absl::FormatSpec<Args...>& format,
+                         Args... args) {
+    Log* inst = MaybeNullInstance();
+    if (inst) {
+      inst->Printf(level, file, line, func, format, args...);
+    } else {
+      DefaultWriteLogMessage(level, file, line,
+                             absl::StrFormat(format, args...).c_str());
+    }
+  }
+
+  template <typename... Args>
+  void Printf(LogLevel level, const char* file, int line, const char* func,
+              const absl::FormatSpec<Args...>& format, Args... args) {
+    if (log_level_ <= level) {
+      WriteLogMessage(level, file, line, func,
+                      absl::StrFormat(format, args...).c_str());
+    }
+  }
+
+  static LogLevel VerbosityToLogLevel(int verbosity);
+
+  void SetLogLevel(LogLevel log_level) { log_level_ = log_level; }
+  LogLevel GetLogLevel() const { return log_level_; }
+
+  virtual ~Log();
+
+ protected:
+  explicit Log(LogLevel log_level) : log_level_(log_level) {}
+
+  virtual void WriteLogMessage(LogLevel level, const char* file, int line,
+                               const char* func, const char* message) = 0;
+
+ private:
+  // A default log writer implementation in case the log was not initialized.
+  static void DefaultWriteLogMessage(LogLevel level, const char* file, int line,
+                                     const char* message);
+
+  // Returns the global log instance.
+  static Log* MaybeNullInstance();
+
+  static Log* instance_;
+
+  LogLevel log_level_;
+};
+
+class ConsoleLog : public Log {
+ public:
+  explicit ConsoleLog(LogLevel log_level) : Log(log_level) {}
+
+ protected:
+  void WriteLogMessage(LogLevel level, const char* file, int line,
+                       const char* func, const char* message) override
+      ABSL_LOCKS_EXCLUDED(mutex_);
+
+ private:
+  absl::Mutex mutex_;
+};
+
+class FileLog : public Log {
+ public:
+  FileLog(LogLevel log_level, const char* path);
+  ~FileLog();
+
+ protected:
+  void WriteLogMessage(LogLevel level, const char* file, int line,
+                       const char* func, const char* message) override
+      ABSL_LOCKS_EXCLUDED(mutex_);
+
+ private:
+  FILE* file_;
+  DefaultSystemClock clock_;
+  absl::Mutex mutex_;
+};
+
+}  // namespace cdc_ft
+
+#endif  // COMMON_LOG_H_