aos/common/logging/logging_interface.h

#ifndef AOS_COMMON_LOGGING_LOGGING_INTERFACE_H_
#define AOS_COMMON_LOGGING_LOGGING_INTERFACE_H_

#include <stdarg.h>

#include <string>
#include <functional>

#include "aos/common/logging/logging.h"

namespace aos {

struct MessageType;

}  // namespace aos

namespace aos {
namespace logging {

// Represents a system that can actually take log messages and do something
// useful with them.
// All of the code (transitively too!) in the DoLog here can make
// normal LOG and LOG_DYNAMIC calls but can NOT call LOG_CORK/LOG_UNCORK. These
// calls will not result in DoLog recursing. However, implementations must be
// safe to call from multiple threads/tasks at the same time. Also, any other
// overriden methods may end up logging through a given implementation's DoLog.
class LogImplementation {
 public:
  LogImplementation() : next_(NULL) {}

  // The one that this one's implementation logs to.
  // NULL means that there is no next one.
  LogImplementation *next() { return next_; }
  // Virtual in case a subclass wants to perform checks. There will be a valid
  // logger other than this one available while this is called.
  virtual void set_next(LogImplementation *next) { next_ = next; }

 private:
  // Actually logs the given message. Implementations should somehow create a
  // LogMessage and then call internal::FillInMessage.
  __attribute__((format(GOOD_PRINTF_FORMAT_TYPE, 3, 0)))
  virtual void DoLog(log_level level, const char *format, va_list ap) = 0;
  __attribute__((format(GOOD_PRINTF_FORMAT_TYPE, 3, 4)))
  void DoLogVariadic(log_level level, const char *format, ...) {
    va_list ap;
    va_start(ap, format);
    DoLog(level, format, ap);
    va_end(ap);
  }

  // Logs the contents of an auto-generated structure. The implementation here
  // just converts it to a string with PrintMessage and then calls DoLog with
  // that, however some implementations can be a lot more efficient than that.
  // size and type are the result of calling Size() and Type() on the type of
  // the message.
  // serialize will call Serialize on the message.
  virtual void LogStruct(log_level level, const ::std::string &message,
                         size_t size, const MessageType *type,
                         const ::std::function<size_t(char *)> &serialize);
  // Similiar to LogStruct, except for matrixes.
  // type_id is the type of the elements of the matrix.
  // data points to rows*cols*type_id.Size() bytes of data in row-major order.
  virtual void LogMatrix(log_level level, const ::std::string &message,
                         uint32_t type_id, int rows, int cols,
                         const void *data);

  // These functions call similar methods on the "current" LogImplementation or
  // Die if they can't find one.
  // levels is how many LogImplementations to not use off the stack.
  static void DoVLog(log_level, const char *format, va_list ap, int levels)
      __attribute__((format(GOOD_PRINTF_FORMAT_TYPE, 2, 0)));
  // This one is implemented in queue_logging.cc.
  static void DoLogStruct(log_level level, const ::std::string &message,
                          size_t size, const MessageType *type,
                          const ::std::function<size_t(char *)> &serialize,
                          int levels);
  // This one is implemented in matrix_logging.cc.
  static void DoLogMatrix(log_level level, const ::std::string &message,
                          uint32_t type_id, int rows, int cols,
                          const void *data, int levels);

  // Friends so that they can access the static Do* functions.
  friend void VLog(log_level, const char *, va_list);
  friend void LogNext(log_level, const char *, ...);
  template <class T>
  friend void DoLogStruct(log_level, const ::std::string &, const T &);
  template <class T>
  friend void DoLogMatrix(log_level, const ::std::string &, const T &);

  LogImplementation *next_;
};

}  // namespace logging
}  // namespace aos

#endif  // AOS_COMMON_LOGGING_LOGGING_INTERFACE_H_