// Copyright (c) 2006, Google Inc.
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// this software without specific prior written permission.
//
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// exception_handler.h:  MacOS exception handler
// This class can install a Mach exception port handler to trap most common
// programming errors.  If an exception occurs, a minidump file will be
// generated which contains detailed information about the process and the
// exception.

#ifndef CLIENT_MAC_HANDLER_EXCEPTION_HANDLER_H__
#define CLIENT_MAC_HANDLER_EXCEPTION_HANDLER_H__

#include <mach/mach.h>

#include <string>

namespace google_airbag {

using std::string;

struct ExceptionParameters;

class ExceptionHandler {
 public:
  // A callback function to run before Airbag performs any substantial
  // processing of an exception.  A FilterCallback is called before writing
  // a minidump.  context is the parameter supplied by the user as
  // callback_context when the handler was created.
  //
  // If a FilterCallback returns true, Airbag will continue processing,
  // attempting to write a minidump.  If a FilterCallback returns false, Airbag
  // will immediately report the exception as unhandled without writing a
  // minidump, allowing another handler the opportunity to handle it.
  typedef bool (*FilterCallback)(void *context);
  
  // A callback function to run after the minidump has been written.
  // |minidump_id| is a unique id for the dump, so the minidump
  // file is <dump_dir>/<minidump_id>.dmp.
  // |context| is the value passed into the constructor. 
  // |succeeded| indicates whether a minidump file was successfully written.
  // Return true if the exception was fully handled and airbag should exit.
  // Return false to allow any other exception handlers to process the 
  // exception.
  typedef bool (*MinidumpCallback)(const char *dump_dir,
                                   const char *minidump_id,
                                   void *context, bool succeeded);

  // Creates a new ExceptionHandler instance to handle writing minidumps.
  // Minidump files will be written to dump_path, and the optional callback
  // is called after writing the dump file, as described above.
  // If install_handler is true, then a minidump will be written whenever
  // an unhandled exception occurs.  If it is false, minidumps will only
  // be written when WriteMinidump is called.
  ExceptionHandler(const string &dump_path, 
                   FilterCallback filter, MinidumpCallback callback,
                   void *callback_context, bool install_handler);
  ~ExceptionHandler();

  // Get and set the minidump path.
  string dump_path() const { return dump_path_; }
  void set_dump_path(const string &dump_path) {
    dump_path_ = dump_path;
    dump_path_c_ = dump_path_.c_str();
    UpdateNextID();  // Necessary to put dump_path_ in next_minidump_path_.
  }
  
  // Writes a minidump immediately.  This can be used to capture the
  // execution state independently of a crash.  Returns true on success.
  bool WriteMinidump();

  // Convenience form of WriteMinidump which does not require an
  // ExceptionHandler instance.
  static bool WriteMinidump(const string &dump_path, MinidumpCallback callback,
                            void *callback_context);

 private:
  // Install the mach exception handler
  bool InstallHandler();

  // Uninstall the mach exception handler (if any)
  bool UninstallHandler();
      
  // Setup the handler thread, and if |install_handler| is true, install the
  // mach exception port handler
  bool Setup(bool install_handler);
    
  // Uninstall the mach exception handler (if any) and terminate the helper
  // thread
  bool Teardown();

  // Send an "empty" mach message to the exception handler.  Return true on
  // success, false otherwise
  bool SendEmptyMachMessage();

  // All minidump writing goes through this one routine
  bool WriteMinidumpWithException(int exception_type, int exception_code,
                                  mach_port_t thread_name);

  // When installed, this static function will be call from a newly created
  // pthread with |this| as the argument
  static void *WaitForMessage(void *exception_handler_class);

  // disallow copy ctor and operator=
  explicit ExceptionHandler(const ExceptionHandler &);
  void operator=(const ExceptionHandler &);

  // Generates a new ID and stores it in next_minidump_id_, and stores the
  // path of the next minidump to be written in next_minidump_path_.
  void UpdateNextID();
  
  // The destination directory for the minidump
  string dump_path_;
  
  // The basename of the next minidump w/o extension
  string next_minidump_id_;
  
  // The full path to the next minidump to be written, including extension
  string next_minidump_path_;
  
  // Pointers to the UTF-8 versions of above
  const char *dump_path_c_;
  const char *next_minidump_id_c_;
  const char *next_minidump_path_c_;

  // The callback function and pointer to be passed back after the minidump
  // has been written
  FilterCallback filter_;
  MinidumpCallback callback_;
  void *callback_context_;

  // The thread that is created for the handler
  pthread_t handler_thread_;

  // The port that is waiting on an exception message to be sent, if the
  // handler is installed
  mach_port_t handler_port_;

  // These variables save the previous exception handler's data so that it
  // can be re-installed when this handler is uninstalled
  ExceptionParameters *previous_;

  // True, if we've installed the exception handler
  bool installed_exception_handler_;
  
  // True, if we're in the process of uninstalling the exception handler and
  // the thread.
  bool is_in_teardown_;
  
  // Save the last result of the last minidump
  bool last_minidump_write_result_;
  
  // A mutex for use when writing out a minidump that was requested on a 
  // thread other than the exception handler.
  pthread_mutex_t minidump_write_mutex_;
  
  // True, if we're using the mutext to indicate when mindump writing occurs
  bool use_minidump_write_mutex_;
};

}  // namespace google_airbag

#endif  // CLIENT_MAC_HANDLER_EXCEPTION_HANDLER_H__