src/main/cpp/mdcpatternconverter.cpp

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <log4cxx/pattern/mdcpatternconverter.h>
#include <log4cxx/private/patternconverter_priv.h>
#include <log4cxx/spi/loggingevent.h>
#include <log4cxx/jsonlayout.h>

using namespace LOG4CXX_NS;
using namespace LOG4CXX_NS::pattern;

IMPLEMENT_LOG4CXX_OBJECT(MDCPatternConverter)

MDCPatternConverter::MDCPatternConverter
	( const LogString&              name
	, const LogString&              style
	, const std::vector<LogString>& options
	)
	: LoggingEventPatternConverter(std::make_unique<PatternConverter::PatternConverterPrivate>(name, style))
{
}

PatternConverterPtr MDCPatternConverter::newInstance(
	const std::vector<LogString>& options)
{
	if (options.empty())
		return std::make_shared<MDCPatternConverter>();
	return std::make_shared<MDCPatternConverter>(LogString(), options.front());
}

void MDCPatternConverter::format( const spi::LoggingEventPtr& event, LogString& toAppendTo ) const
{
	size_t startIndex = toAppendTo.size();
	auto& info = getFormattingInfo();
	if (m_priv->name.empty()) // Full MDC required?
	{
		const size_t separCount = 2;
		const size_t quoteCount = 2;
		LogString separ = LOG4CXX_STR("{");
		size_t remainingLength = info.getMaxLength() > 0
			? static_cast<size_t>(info.getMaxLength()) - 1
			: 0;
		for (auto key : event->getMDCKeySet())
		{
			LogString value;
			event->getMDC(key, value);
			auto itemLength = separCount + key.length() + quoteCount + value.length() + quoteCount;
			if (remainingLength < itemLength)
				break;
			toAppendTo.append(separ);
			JSONLayout::appendItem(key, toAppendTo);
			toAppendTo.append(LOG4CXX_STR(":"));
			JSONLayout::appendItem(value, toAppendTo);
			separ = LOG4CXX_STR(",");
			remainingLength -= itemLength;
		}
		if (LOG4CXX_STR(",") == separ)
			toAppendTo.append(LOG4CXX_STR("}"));
	}
	else
	{
		LogString value;
		event->getMDC(m_priv->name, value);
		if (info.getMaxLength() < value.length())
			toAppendTo.append(value.substr(value.length() - info.getMaxLength()));
		else
			toAppendTo.append(value);
	}
	if (!m_priv->style.empty()) // In a quoted context?
	{
		auto quote = m_priv->style.front();
		if (toAppendTo.find(quote, startIndex) != toAppendTo.npos)
		{
			// Duplicate each quote character in a single linear pass:
			// repeated single-character insert() shifts the tail of the
			// output buffer on every quote, which is quadratic in the
			// (attacker-controllable) MDC content length.
			LogString input = toAppendTo.substr(startIndex);
			toAppendTo.resize(startIndex);
			size_t endIndex, index = 0;
			while ((endIndex = input.find(quote, index)) != input.npos)
			{
				toAppendTo.append(input, index, endIndex - index + 1);
				toAppendTo += quote;
				index = endIndex + 1;
			}
			toAppendTo.append(input, index, LogString::npos);
		}
	}
}