src/hotspot/share/logging/logStream.hpp

/*
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 * 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_LOGSTREAM_HPP
#define SHARE_LOGGING_LOGSTREAM_HPP

#include "logging/log.hpp"
#include "logging/logHandle.hpp"
#include "logging/logMessage.hpp"
#include "utilities/ostream.hpp"

class LogStreamImplBase : public outputStream {
  friend class LogStreamTest_TestLineBufferAllocation_vm_Test;
  friend class LogStreamTest_TestLineBufferAllocationCap_vm_Test;

  // No heap allocation of LogStream.
  static void* operator new   (size_t) = delete;
  static void* operator new[] (size_t) = delete;

  // Helper class, maintains the line buffer. For small line lengths,
  // we avoid malloc and use a fixed sized member char array. If LogStream
  // is allocated on the stack, this means small lines are assembled
  // directly on the stack.
  class LineBuffer {
    char _smallbuf[64];
    char* _buf;
    size_t _cap;
    size_t _pos;
    bool try_ensure_cap(size_t cap);

  public:
    LineBuffer();
    ~LineBuffer();
    bool is_empty() const {
      return _pos == 0;
    }
    const char* buffer() const {
      return _buf;
    }
    void append(const char* s, size_t len);
    void reset();
  };

protected:
  LineBuffer _current_line;
};

template <typename BackingLog>
class LogStreamImpl : public LogStreamImplBase {
private:
  BackingLog _backing_log;

public:
  explicit LogStreamImpl(BackingLog bl)
    : _backing_log(bl) {};

  ~LogStreamImpl() override;

  bool is_enabled() {
    return _backing_log.is_enabled();
  }

  void write(const char* s, size_t len) override;
};

class LogStream : public LogStreamImpl<LogTargetHandle> {
  // see test/hotspot/gtest/logging/test_logStream.cpp
  friend class LogStreamTest_TestLineBufferAllocation_vm_Test;
  friend class LogStreamTest_TestLineBufferAllocationCap_vm_Test;

  NONCOPYABLE(LogStream);

public:
  // Constructor to support creation from a LogTarget instance.
  //
  // LogTarget(Debug, gc) log;
  // LogStream(log) stream;
  template <LogLevelType level, LogTagType T0, LogTagType T1, LogTagType T2, LogTagType T3, LogTagType T4, LogTagType GuardTag>
  LogStream(const LogTargetImpl<level, T0, T1, T2, T3, T4, GuardTag>& type_carrier)
    : LogStreamImpl(LogTargetHandle(level, LogTagSetMapping<T0, T1, T2, T3, T4>::tagset())) {}

  // Constructor to support creation from typed (likely null) pointer. Mostly used by the logging framework.
  //
  // LogStream stream(log.debug());
  //  or
  // LogStream stream((LogTargetImpl<level, T0, T1, T2, T3, T4, GuardTag>*)nullptr);
  template <LogLevelType level, LogTagType T0, LogTagType T1, LogTagType T2, LogTagType T3, LogTagType T4, LogTagType GuardTag>
  LogStream(const LogTargetImpl<level, T0, T1, T2, T3, T4, GuardTag>* type_carrier)
    : LogStreamImpl(LogTargetHandle(level, LogTagSetMapping<T0, T1, T2, T3, T4>::tagset())) {}

  // Constructor to support creation from a LogTargetHandle.
  //
  // LogTarget(Debug, gc) log;
  // LogTargetHandle(log) handle;
  // LogStream stream(handle);
  LogStream(LogTargetHandle handle)
    : LogStreamImpl(handle) {}

  // Constructor to support creation from a log level and tagset.
  //
  // LogStream(level, tageset);
  LogStream(LogLevelType level, LogTagSet& tagset)
    : LogStreamImpl(LogTargetHandle(level, tagset)) {}

  // Destructor writes any unfinished output left in the line buffer.
};

// Support creation of a LogStream without having to provide a LogTarget pointer.
#define LogStreamHandle(level, ...) LogStreamTemplate<LogLevel::level, LOG_TAGS(__VA_ARGS__)>

template <LogLevelType level, LogTagType T0, LogTagType T1, LogTagType T2, LogTagType T3, LogTagType T4, LogTagType GuardTag>
class LogStreamTemplate : public LogStream {
public:
  LogStreamTemplate()
    : LogStream((LogTargetImpl<level, T0, T1, T2, T3, T4, GuardTag>*)nullptr) {}
};

class LogMessageHandle {
  const LogLevelType _level;
  LogMessageImpl& _lm;

public:
  LogMessageHandle(const LogLevelType level, LogMessageImpl& lm)
    : _level(level), _lm(lm) {}

  bool is_enabled() {
    return _lm.is_level(_level);
  }

  void print(const char* fmt, ...) ATTRIBUTE_PRINTF(2, 3) {
    va_list args;
    va_start(args, fmt);
    if (is_enabled()) {
      _lm.vwrite(_level, fmt, args);
    }
    va_end(args);
  }
};

class NonInterleavingLogStream : public LogStreamImpl<LogMessageHandle> {
public:
  NonInterleavingLogStream(LogLevelType level, LogMessageImpl& lm)
    : LogStreamImpl(LogMessageHandle(level, lm)) {}
};

#endif // SHARE_LOGGING_LOGSTREAM_HPP