JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#ifndef SHARE_LOGGING_LOGCONFIGURATION_HPP
#define SHARE_LOGGING_LOGCONFIGURATION_HPP

#include "logging/logLevel.hpp"
#include "memory/allocation.hpp"
#include "utilities/globalDefinitions.hpp"

class LogOutput;
class LogDecorators;
class LogSelectionList;

// Global configuration of logging. Handles parsing and configuration of the logging framework,
// and manages the list of configured log outputs. The actual tag and level configuration is
// kept implicitly in the LogTagSets and their LogOutputLists. During configuration the tagsets
// are iterated over and updated accordingly.
class LogConfiguration : public AllStatic {
 friend class VMError;
 friend class LogTestFixture;
 public:
  // Function for listeners
  typedef void (*UpdateListenerFunction)(void);

  // Register callback for config change.
  // The callback is always called with ConfigurationLock held,
  // hence doing log reconfiguration from the callback will deadlock.
  // The main Java thread may call this callback if there is an early registration
  // else the attach listener JavaThread, started via diagnostic command, will be executing thread.
  // The main purpose of this callback is to see if a loglevel have been changed.
  // There is no way to unregister.
  static void register_update_listener(UpdateListenerFunction cb);

 private:
  static LogOutput**  _outputs;
  static size_t       _n_outputs;

  static UpdateListenerFunction*    _listener_callbacks;
  static size_t                     _n_listener_callbacks;

  // Create a new output. Returns NULL if failed.
  static LogOutput* new_output(const char* name, const char* options, outputStream* errstream);

  // Add an output to the list of configured outputs. Returns the assigned index.
  static size_t add_output(LogOutput* out);

  // Delete a configured output. The stderr/stdout outputs can not be removed.
  // Output should be completely disabled before it is deleted.
  static void delete_output(size_t idx);

  // Disable all logging to the specified output and then delete it (unless it is stdout/stderr).
  static void disable_output(size_t idx);

  // Get output index by name. Returns SIZE_MAX if output not found.
  static size_t find_output(const char* name);

  // Configure output (add or update existing configuration) to log on tag-level combination using specified decorators.
  static void configure_output(size_t idx, const LogSelectionList& tag_level_expression, const LogDecorators& decorators);

  // This should be called after any configuration change while still holding ConfigurationLock
  static void notify_update_listeners();

  // Respectively describe the built-in and runtime dependent portions of the configuration.
  static void describe_available(outputStream* out);
  static void describe_current_configuration(outputStream* out);


 public:
  // Initialization and finalization of log configuration, to be run at vm startup and shutdown respectively.
  static void initialize(jlong vm_start_time);
  static void finalize();

  // Perform necessary post-initialization after VM startup. Enables reconfiguration of logging.
  static void post_initialize();

  // Disable all logging, equivalent to -Xlog:disable.
  static void disable_logging();

  // Configures logging on stdout for the given tags and level combination.
  // Intended for mappings between -XX: flags and Unified Logging configuration.
  // If exact_match is true, only tagsets with precisely the specified tags will be configured
  // (exact_match=false is the same as "-Xlog:<tags>*=<level>", and exact_match=true is "-Xlog:<tags>=<level>").
  // Tags should be specified using the LOG_TAGS macro, e.g.
  // LogConfiguration::configure_stdout(LogLevel::<level>, <true/false>, LOG_TAGS(<tags>));
  static void configure_stdout(LogLevelType level, int exact_match, ...);

  // Parse command line configuration. Parameter 'opts' is the string immediately following the -Xlog: argument ("gc" for -Xlog:gc).
  static bool parse_command_line_arguments(const char* opts = "all");

  // Parse separated configuration arguments (from JCmd/MBean and command line).

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