implement C++ logger (#575)

* implement logger, apple impl and other impl, with test.

* some minor fixes

*   re-organize cmake build rules;
*   fix bugs in log_apple.mm;

* style fix by style.sh

* Complete removal of LogAssert

1 files changed, 63 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/util/log.h b/Firestore/core/src/firebase/firestore/util/log.h
new file mode 100644
index 0000000..d0cff4d
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/util/log.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright 2017 Google
+ *
+ * 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 FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_LOG_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_LOG_H_
+
+#include <stdarg.h>
+
+namespace firebase {
+namespace firestore {
+namespace util {
+
+/// @brief Levels used when logging messages.
+enum LogLevel {
+  /// Verbose Log Level
+  kLogLevelVerbose = 0,
+  /// Debug Log Level
+  kLogLevelDebug,
+  /// Info Log Level
+  kLogLevelInfo,
+  /// Warning Log Level
+  kLogLevelWarning,
+  /// Error Log Level
+  kLogLevelError,
+};
+
+// Common log methods.
+
+// All messages at or above the specified log level value are displayed.
+void LogSetLevel(LogLevel level);
+// Get the currently set log level.
+LogLevel LogGetLevel();
+// Log a debug message to the system log.
+void LogDebug(const char* format, ...);
+// Log an info message to the system log.
+void LogInfo(const char* format, ...);
+// Log a warning to the system log.
+void LogWarning(const char* format, ...);
+// Log an error to the system log.
+void LogError(const char* format, ...);
+// Log a firebase message (implemented by the platform specific logger).
+void LogMessageV(LogLevel log_level, const char* format, va_list args);
+// Log a firebase message via LogMessageV().
+void LogMessage(LogLevel log_level, const char* format, ...);
+
+}  // namespace util
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_UTIL_LOG_H_