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High-Performance FIX Gateway
/*
* Copyright 2015-2023 Real Logic Limited.
*
* Licensed 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
*
* https://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.
*/
package uk.co.real_logic.artio.otf;
import org.agrona.DirectBuffer;
import org.agrona.collections.IntHashSet;
import uk.co.real_logic.artio.dictionary.LongDictionary;
import uk.co.real_logic.artio.fields.AsciiFieldFlyweight;
import uk.co.real_logic.artio.util.AsciiBuffer;
import uk.co.real_logic.artio.util.MutableAsciiBuffer;
import static uk.co.real_logic.artio.ValidationError.INVALID_CHECKSUM;
import static uk.co.real_logic.artio.ValidationError.PARSE_ERROR;
import static uk.co.real_logic.artio.dictionary.SessionConstants.*;
import static uk.co.real_logic.artio.otf.MessageControl.STOP;
import static uk.co.real_logic.artio.util.AsciiBuffer.UNKNOWN_INDEX;
/**
* Zero allocation generic parser for fix messages.
*
* Take care when refactoring:
*
* There are a lot of places where values are passed as parameters and not assigned to fields in order to
* allow stack allocated primitives and avoid allocation.
*/
public final class OtfParser
{
private static final int NO_CHECKSUM = -2;
private static final int UNKNOWN = -1;
private final AsciiBuffer string = new MutableAsciiBuffer();
private final AsciiFieldFlyweight stringField = new AsciiFieldFlyweight();
private final OtfMessageAcceptor acceptor;
private final LongDictionary groupToField;
private int checksum;
private int checksumOffset;
private long messageType;
private int tag;
public OtfParser(final OtfMessageAcceptor acceptor, final LongDictionary groupToField)
{
this.acceptor = acceptor;
this.groupToField = groupToField;
}
public void onMessage(final DirectBuffer buffer, final int offset, final int length)
{
string.wrap(buffer);
if (acceptor.onNext() == STOP)
{
return;
}
tag = UNKNOWN;
this.messageType = UNKNOWN;
checksum = NO_CHECKSUM;
checksumOffset = 0;
try
{
if (parseFields(offset, offset + length, UNKNOWN, null, 0) < 0)
{
return;
}
if (validChecksum(offset, checksum))
{
acceptor.onComplete();
}
else
{
invalidChecksum(this.messageType);
}
}
catch (final NumberFormatException ex)
{
parseError(this.messageType, tag);
}
}
private int parseFields(
final int offset,
final int end,
final int groupTag,
final IntHashSet groupFields,
final int numberOfElementsInGroup)
{
int firstFieldInGroup = UNKNOWN;
int indexOfGroupElement = 0;
int position = offset;
while (position < end)
{
final int equalsPosition = string.scan(position, end, '=');
if (!validatePosition(equalsPosition, acceptor))
{
return position;
}
tag = string.getNatural(position, equalsPosition);
final int valueOffset = equalsPosition + 1;
final int endOfField = string.scan(valueOffset, end, START_OF_HEADER);
if (!validatePosition(endOfField, acceptor))
{
return position;
}
final int valueLength = endOfField - valueOffset;
final IntHashSet newGroupFields = groupToField.values(tag);
if (newGroupFields == null)
{
if (insideAGroup(groupTag))
{
if (isEndOfGroup(groupFields))
{
groupEnd(groupTag, numberOfElementsInGroup, indexOfGroupElement);
return position;
}
else
{
// First field first iteration
if (firstFieldInGroup == UNKNOWN)
{
firstFieldInGroup = tag;
}
// We've seen the first field again - its a new group iteration
else if (tag == firstFieldInGroup)
{
if (groupEnd(groupTag, numberOfElementsInGroup, indexOfGroupElement) == STOP)
{
return position;
}
indexOfGroupElement++;
if (groupBegin(groupTag, numberOfElementsInGroup, indexOfGroupElement) == STOP)
{
return position;
}
}
}
}
final MessageControl control = acceptor.onField(tag, string, valueOffset, valueLength);
collectImportantFields(equalsPosition, valueOffset, endOfField, valueLength);
position = endOfField + 1;
if (control == STOP)
{
return ~position;
}
}
else
{
if (insideAGroup(groupTag) && isEndOfGroup(groupFields))
{
groupEnd(groupTag, numberOfElementsInGroup, indexOfGroupElement);
return position;
}
else
{
position = parseGroup(tag, valueOffset, endOfField, end, newGroupFields);
if (position < 0)
{
return position;
}
}
}
}
return position;
}
private int parseGroup(
final int tag,
final int valueOffset,
final int endOfField,
final int end,
final IntHashSet groupFields)
{
final int numberOfElements = string.getNatural(valueOffset, endOfField);
acceptor.onGroupHeader(tag, numberOfElements);
if (numberOfElements > 0)
{
if (groupBegin(tag, numberOfElements, 0) == STOP)
{
return ~endOfField;
}
final int position = parseFields(endOfField + 1, end, tag, groupFields, numberOfElements);
if (position == end)
{
if (groupEnd(tag, numberOfElements, numberOfElements - 1) == STOP)
{
return ~position;
}
}
return position;
}
return endOfField;
}
private boolean isEndOfGroup(final IntHashSet groupFields)
{
return !groupFields.contains(tag);
}
private void collectImportantFields(
final int equalsPosition,
final int valueOffset,
final int endOfField,
final int valueLength)
{
if (tag == CHECKSUM)
{
checksum = string.getNatural(valueOffset, endOfField);
checksumOffset = equalsPosition - 2;
}
else if (tag == MESSAGE_TYPE)
{
messageType = string.getMessageType(valueOffset, valueLength);
}
}
private boolean insideAGroup(final int tag)
{
return tag != UNKNOWN;
}
private MessageControl groupBegin(final int tag, final int numberOfElements, final int index)
{
return acceptor.onGroupBegin(tag, numberOfElements, index);
}
private MessageControl groupEnd(final int tag, final int numberOfElements, final int index)
{
return acceptor.onGroupEnd(tag, numberOfElements, index);
}
private boolean parseError(final long messageType, final int tag)
{
return acceptor.onError(PARSE_ERROR, messageType, tag, stringField);
}
private boolean invalidChecksum(final long messageType)
{
return acceptor.onError(INVALID_CHECKSUM, messageType, CHECKSUM, stringField);
}
private boolean validatePosition(final int position, final OtfMessageAcceptor acceptor)
{
if (position == UNKNOWN_INDEX)
{
// null because there's no actual field data at this point.
acceptor.onError(PARSE_ERROR, messageType, tag, null);
return false;
}
return true;
}
private boolean validChecksum(final int offset, final int messageChecksum)
{
if (messageChecksum == NO_CHECKSUM)
{
return false;
}
final int correctChecksum = string.computeChecksum(offset, checksumOffset);
return correctChecksum == messageChecksum;
}
}