src/hotspot/share/logging/logStream.cpp

/*
 * Copyright (c) 2016, 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"

LogStream::LineBuffer::LineBuffer()
 : _buf(_smallbuf), _cap(sizeof(_smallbuf)), _pos(0)
{
  _buf[0] = '\0';
}

LogStream::LineBuffer::~LineBuffer() {
  assert(_pos == 0, "still outstanding bytes in the line buffer");
  if (_buf != _smallbuf) {
    os::free(_buf);
  }
}

// try_ensure_cap tries to enlarge the capacity of the internal buffer
// to the given atleast value. May fail if either OOM happens or atleast
// is larger than a reasonable max of 1 M. Caller must not assume
// capacity without checking.
void LogStream::LineBuffer::try_ensure_cap(size_t atleast) {
  assert(_cap >= sizeof(_smallbuf), "sanity");
  if (_cap < atleast) {
    // Cap out at a reasonable max to prevent runaway leaks.
    const size_t reasonable_max = 1 * M;
    assert(_cap <= reasonable_max, "sanity");
    if (_cap == reasonable_max) {
      return;
    }

    const size_t additional_expansion = 256;
    size_t newcap = align_up(atleast + additional_expansion, additional_expansion);
    if (newcap > reasonable_max) {
      log_info(logging)("Suspiciously long log line: \"%.100s%s",
              _buf, (_pos >= 100 ? "..." : ""));
      newcap = reasonable_max;
    }

    char* const newbuf = (char*) os::malloc(newcap, mtLogging);
    if (newbuf == NULL) { // OOM. Leave object unchanged.
      return;
    }
    if (_pos > 0) { // preserve old content
      memcpy(newbuf, _buf, _pos + 1); // ..including trailing zero
    }
    if (_buf != _smallbuf) {
      os::free(_buf);
    }
    _buf = newbuf;
    _cap = newcap;
  }
  assert(_cap >= atleast, "sanity");
}

void LogStream::LineBuffer::append(const char* s, size_t len) {
  assert(_buf[_pos] == '\0', "sanity");
  assert(_pos < _cap, "sanity");
  const size_t minimum_capacity_needed = _pos + len + 1;
  try_ensure_cap(minimum_capacity_needed);
  // try_ensure_cap may not have enlarged the capacity to the full requested
  // extend or may have not worked at all. In that case, just gracefully work
  // with what we have already; just truncate if necessary.
  if (_cap < minimum_capacity_needed) {
    len = _cap - _pos - 1;
    if (len == 0) {
      return;
    }
  }
  memcpy(_buf + _pos, s, len);
  _pos += len;
  _buf[_pos] = '\0';
}

void LogStream::LineBuffer::reset() {
  _pos = 0;
  _buf[_pos] = '\0';
}

void LogStream::write(const char* s, size_t len) {
  if (len > 0 && s[len - 1] == '\n') {
    _current_line.append(s, len - 1); // omit the newline.
    _log_handle.print("%s", _current_line.buffer());
    _current_line.reset();
  } else {
    _current_line.append(s, len);
  }
  update_position(s, len);
}

// Destructor writes any unfinished output left in the line buffer.
LogStream::~LogStream() {
  if (_current_line.is_empty() == false) {
    _log_handle.print("%s", _current_line.buffer());
    _current_line.reset();
  }
}