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/*
* Copyright 2013-2024 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.sbe.otf;
import org.agrona.DirectBuffer;
import uk.co.real_logic.sbe.ir.Token;
import java.util.List;
import static uk.co.real_logic.sbe.ir.Signal.BEGIN_FIELD;
import static uk.co.real_logic.sbe.ir.Signal.BEGIN_GROUP;
import static uk.co.real_logic.sbe.ir.Signal.BEGIN_VAR_DATA;
/**
* On-the-fly decoder that dynamically decodes messages based on the IR for a schema.
*
* The contents of the messages are structurally decomposed and passed to a {@link TokenListener} for decoding the
* primitive values.
*
* The design keeps all state on the stack to maximise performance and avoid object allocation. The message decoder can
* be reused repeatably by calling {@link OtfMessageDecoder#decode(DirectBuffer, int, int, int, List, TokenListener)}
* which is thread safe to be used across multiple threads.
*/
@SuppressWarnings("FinalParameters")
public class OtfMessageDecoder
{
/**
* Decode a message from the provided buffer based on the message schema described with IR {@link Token}s.
*
* @param buffer containing the encoded message.
* @param offset at which the message encoding starts in the buffer.
* @param actingVersion of the encoded message for dealing with extension fields.
* @param blockLength of the root message fields.
* @param msgTokens in IR format describing the message structure.
* @param listener to callback for decoding the primitive values as discovered in the structure.
* @return the index in the underlying buffer after decoding.
*/
public static int decode(
final DirectBuffer buffer,
final int offset,
final int actingVersion,
final int blockLength,
final List msgTokens,
final TokenListener listener)
{
listener.onBeginMessage(msgTokens.get(0));
int i = offset;
final int numTokens = msgTokens.size();
final int tokenIdx = decodeFields(buffer, i, actingVersion, msgTokens, 1, numTokens, listener);
i += blockLength;
final long packedValues = decodeGroups(
buffer, i, actingVersion, msgTokens, tokenIdx, numTokens, listener);
i = decodeData(
buffer,
bufferOffset(packedValues),
msgTokens,
tokenIndex(packedValues),
numTokens,
actingVersion,
listener);
listener.onEndMessage(msgTokens.get(numTokens - 1));
return i;
}
private static int decodeFields(
final DirectBuffer buffer,
final int bufferOffset,
final int actingVersion,
final List tokens,
final int tokenIndex,
final int numTokens,
final TokenListener listener)
{
int i = tokenIndex;
while (i < numTokens)
{
final Token fieldToken = tokens.get(i);
if (BEGIN_FIELD != fieldToken.signal())
{
break;
}
final int nextFieldIdx = i + fieldToken.componentTokenCount();
i++;
final Token typeToken = tokens.get(i);
final int offset = typeToken.offset();
switch (typeToken.signal())
{
case BEGIN_COMPOSITE:
decodeComposite(
fieldToken,
buffer,
bufferOffset + offset,
tokens, i,
nextFieldIdx - 2,
actingVersion,
listener);
break;
case BEGIN_ENUM:
listener.onEnum(
fieldToken, buffer, bufferOffset + offset, tokens, i, nextFieldIdx - 2, actingVersion);
break;
case BEGIN_SET:
listener.onBitSet(
fieldToken, buffer, bufferOffset + offset, tokens, i, nextFieldIdx - 2, actingVersion);
break;
case ENCODING:
listener.onEncoding(fieldToken, buffer, bufferOffset + offset, typeToken, actingVersion);
break;
default:
break;
}
i = nextFieldIdx;
}
return i;
}
private static long decodeGroups(
final DirectBuffer buffer,
int bufferOffset,
final int actingVersion,
final List tokens,
int tokenIdx,
final int numTokens,
final TokenListener listener)
{
while (tokenIdx < numTokens)
{
final Token token = tokens.get(tokenIdx);
if (BEGIN_GROUP != token.signal())
{
break;
}
final boolean isPresent = token.version() <= actingVersion;
final Token blockLengthToken = tokens.get(tokenIdx + 2);
final int blockLength = isPresent ? Types.getInt(
buffer,
bufferOffset + blockLengthToken.offset(),
blockLengthToken.encoding().primitiveType(),
blockLengthToken.encoding().byteOrder()) : 0;
final Token numInGroupToken = tokens.get(tokenIdx + 3);
final int numInGroup = isPresent ? Types.getInt(
buffer,
bufferOffset + numInGroupToken.offset(),
numInGroupToken.encoding().primitiveType(),
numInGroupToken.encoding().byteOrder()) : 0;
final Token dimensionTypeComposite = tokens.get(tokenIdx + 1);
if (isPresent)
{
bufferOffset += dimensionTypeComposite.encodedLength();
}
final int beginFieldsIdx = tokenIdx + dimensionTypeComposite.componentTokenCount() + 1;
listener.onGroupHeader(token, numInGroup);
for (int i = 0; i < numInGroup; i++)
{
listener.onBeginGroup(token, i, numInGroup);
final int afterFieldsIdx = decodeFields(
buffer, bufferOffset, actingVersion, tokens, beginFieldsIdx, numTokens, listener);
bufferOffset += blockLength;
final long packedValues = decodeGroups(
buffer, bufferOffset, actingVersion, tokens, afterFieldsIdx, numTokens, listener);
bufferOffset = decodeData(
buffer,
bufferOffset(packedValues),
tokens,
tokenIndex(packedValues),
numTokens,
actingVersion,
listener);
listener.onEndGroup(token, i, numInGroup);
}
tokenIdx += token.componentTokenCount();
}
return pack(bufferOffset, tokenIdx);
}
private static void decodeComposite(
final Token fieldToken,
final DirectBuffer buffer,
final int bufferOffset,
final List tokens,
final int tokenIdx,
final int toIndex,
final int actingVersion,
final TokenListener listener)
{
listener.onBeginComposite(fieldToken, tokens, tokenIdx, toIndex);
for (int i = tokenIdx + 1; i < toIndex; )
{
final Token typeToken = tokens.get(i);
final int nextFieldIdx = i + typeToken.componentTokenCount();
final int offset = typeToken.offset();
switch (typeToken.signal())
{
case BEGIN_COMPOSITE:
decodeComposite(
fieldToken,
buffer,
bufferOffset + offset,
tokens, i,
nextFieldIdx - 1,
actingVersion,
listener);
break;
case BEGIN_ENUM:
listener.onEnum(
fieldToken, buffer, bufferOffset + offset, tokens, i, nextFieldIdx - 1, actingVersion);
break;
case BEGIN_SET:
listener.onBitSet(
fieldToken, buffer, bufferOffset + offset, tokens, i, nextFieldIdx - 1, actingVersion);
break;
case ENCODING:
listener.onEncoding(typeToken, buffer, bufferOffset + offset, typeToken, actingVersion);
break;
default:
break;
}
i += typeToken.componentTokenCount();
}
listener.onEndComposite(fieldToken, tokens, tokenIdx, toIndex);
}
private static int decodeData(
final DirectBuffer buffer,
int bufferOffset,
final List tokens,
int tokenIdx,
final int numTokens,
final int actingVersion,
final TokenListener listener)
{
while (tokenIdx < numTokens)
{
final Token token = tokens.get(tokenIdx);
if (BEGIN_VAR_DATA != token.signal())
{
break;
}
final boolean isPresent = token.version() <= actingVersion;
final Token lengthToken = tokens.get(tokenIdx + 2);
final int length = isPresent ? Types.getInt(
buffer,
bufferOffset + lengthToken.offset(),
lengthToken.encoding().primitiveType(),
lengthToken.encoding().byteOrder()) : 0;
final Token dataToken = tokens.get(tokenIdx + 3);
if (isPresent)
{
bufferOffset += dataToken.offset();
}
listener.onVarData(token, buffer, bufferOffset, length, dataToken);
bufferOffset += length;
tokenIdx += token.componentTokenCount();
}
return bufferOffset;
}
private static long pack(final int bufferOffset, final int tokenIndex)
{
return ((long)bufferOffset << 32) | tokenIndex;
}
private static int bufferOffset(final long packedValues)
{
return (int)(packedValues >>> 32);
}
private static int tokenIndex(final long packedValues)
{
return (int)packedValues;
}
}