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[Java] Add tryClaim API to the RingBuffer #199

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Jan 20, 2020
Merged

[Java] Add tryClaim API to the RingBuffer #199

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116 changes: 89 additions & 27 deletions agrona/src/main/java/org/agrona/concurrent/ringbuffer/ManyToOneRingBuffer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,17 +27,8 @@
/**
* A ring-buffer that supports the exchange of messages from many producers to a single consumer.
*/
public class ManyToOneRingBuffer implements RingBuffer
public final class ManyToOneRingBuffer implements RingBuffer
{
/**
* Record type is padding to prevent fragmentation in the buffer.
*/
public static final int PADDING_MSG_TYPE_ID = -1;

/**
* Buffer has insufficient capacity to record a message.
*/
private static final int INSUFFICIENT_CAPACITY = -2;

private final int capacity;
private final int maxMsgLength;
Expand Down Expand Up @@ -84,31 +75,27 @@ public int capacity()
/**
* {@inheritDoc}
*/
public boolean write(final int msgTypeId, final DirectBuffer srcBuffer, final int srcIndex, final int length)
public boolean write(final int msgTypeId, final DirectBuffer srcBuffer, final int offset, final int length)
{
checkTypeId(msgTypeId);
checkMsgLength(length);

boolean isSuccessful = false;

final AtomicBuffer buffer = this.buffer;
final int recordLength = length + HEADER_LENGTH;
final int requiredCapacity = align(recordLength, ALIGNMENT);
final int recordIndex = claimCapacity(buffer, requiredCapacity);
final int recordIndex = claimCapacity(buffer, recordLength);

if (INSUFFICIENT_CAPACITY != recordIndex)
if (INSUFFICIENT_CAPACITY == recordIndex)
{
buffer.putIntOrdered(lengthOffset(recordIndex), -recordLength);
UnsafeAccess.UNSAFE.storeFence();

buffer.putInt(typeOffset(recordIndex), msgTypeId);
buffer.putBytes(encodedMsgOffset(recordIndex), srcBuffer, srcIndex, length);
buffer.putIntOrdered(lengthOffset(recordIndex), recordLength);

isSuccessful = true;
return false;
}

return isSuccessful;
buffer.putIntOrdered(lengthOffset(recordIndex), -recordLength);
UnsafeAccess.UNSAFE.storeFence();

buffer.putInt(typeOffset(recordIndex), msgTypeId);
buffer.putBytes(encodedMsgOffset(recordIndex), srcBuffer, offset, length);
buffer.putIntOrdered(lengthOffset(recordIndex), recordLength);
return true;
}

/**
Expand Down Expand Up @@ -305,6 +292,55 @@ else if (0 == length)
return unblocked;
}

/**
* {@inheritDoc}
*/
public int tryClaim(final int msgTypeId, final int length)
{
checkTypeId(msgTypeId);
checkMsgLength(length);

final AtomicBuffer buffer = this.buffer;
final int recordLength = length + HEADER_LENGTH;
final int recordIndex = claimCapacity(buffer, recordLength);

if (INSUFFICIENT_CAPACITY == recordIndex)
{
return recordIndex;
}

buffer.putIntOrdered(lengthOffset(recordIndex), -recordLength);
UnsafeAccess.UNSAFE.storeFence();
buffer.putInt(typeOffset(recordIndex), msgTypeId);

return encodedMsgOffset(recordIndex);
}

/**
* {@inheritDoc}
*/
public void commit(final int index)
{
final int recordIndex = computeRecordIndex(index);
final AtomicBuffer buffer = this.buffer;
final int recordLength = verifyClaimedSpaceNotReleased(buffer, recordIndex);

buffer.putIntOrdered(lengthOffset(recordIndex), -recordLength);
}

/**
* {@inheritDoc}
*/
public void abort(final int index)
{
final int recordIndex = computeRecordIndex(index);
final AtomicBuffer buffer = this.buffer;
final int recordLength = verifyClaimedSpaceNotReleased(buffer, recordIndex);

buffer.putInt(typeOffset(recordIndex), PADDING_MSG_TYPE_ID);
buffer.putIntOrdered(lengthOffset(recordIndex), -recordLength);
}

private static boolean scanBackToConfirmStillZeroed(final AtomicBuffer buffer, final int from, final int limit)
{
int i = from - ALIGNMENT;
Expand All @@ -325,15 +361,20 @@ private static boolean scanBackToConfirmStillZeroed(final AtomicBuffer buffer, f

private void checkMsgLength(final int length)
{
if (length > maxMsgLength)
if (length < 0)
{
throw new IllegalArgumentException("invalid message length=" + length);
}
else if (length > maxMsgLength)
{
throw new IllegalArgumentException(
"encoded message exceeds maxMsgLength of " + maxMsgLength + ", length=" + length);
}
}

private int claimCapacity(final AtomicBuffer buffer, final int requiredCapacity)
private int claimCapacity(final AtomicBuffer buffer, final int recordLength)
{
final int requiredCapacity = align(recordLength, ALIGNMENT);
final int capacity = this.capacity;
final int tailPositionIndex = this.tailPositionIndex;
final int headCachePositionIndex = this.headCachePositionIndex;
Expand Down Expand Up @@ -398,4 +439,25 @@ private int claimCapacity(final AtomicBuffer buffer, final int requiredCapacity)

return tailIndex;
}

private int computeRecordIndex(final int index)
{
final int recordIndex = index - HEADER_LENGTH;
if (recordIndex < 0 || recordIndex > (capacity - HEADER_LENGTH))
{
throw new IllegalArgumentException("invalid message index " + index);
}
return recordIndex;
}

private int verifyClaimedSpaceNotReleased(final AtomicBuffer buffer, final int recordIndex)
{
final int recordLength = buffer.getInt(lengthOffset(recordIndex));
if (recordLength < 0)
{
return recordLength;
}
throw new IllegalStateException("claimed space was already " +
(PADDING_MSG_TYPE_ID == buffer.getInt(typeOffset(recordIndex)) ? "aborted" : "committed"));
}
}
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