io.aeron.logbuffer.BufferClaim Maven / Gradle / Ivy
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/*
* Copyright 2014-2021 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 io.aeron.logbuffer;
import org.agrona.DirectBuffer;
import org.agrona.MutableDirectBuffer;
import org.agrona.concurrent.AtomicBuffer;
import org.agrona.concurrent.UnsafeBuffer;
import java.nio.ByteOrder;
import static io.aeron.protocol.DataHeaderFlyweight.*;
import static java.nio.ByteOrder.LITTLE_ENDIAN;
/**
* Represents a claimed range in a buffer to be used for recording a message without copy semantics for later commit.
*
* The claimed space is in {@link #buffer()} between {@link #offset()} and {@link #offset()} + {@link #length()}.
* When the buffer is filled with message data, use {@link #commit()} to make it available to subscribers.
*
* If the claimed space is no longer required it can be aborted by calling {@link #abort()}.
*
* @see io.aeron.Publication#tryClaim(int, BufferClaim)
*/
public final class BufferClaim
{
private final UnsafeBuffer buffer = new UnsafeBuffer(0, 0);
/**
* Wrap a region of an underlying log buffer so can can represent a claimed space for use by a publisher.
*
* @param buffer to be wrapped.
* @param offset at which the claimed region begins including space for the header.
* @param length length of the underlying claimed region including space for the header.
*/
public void wrap(final AtomicBuffer buffer, final int offset, final int length)
{
this.buffer.wrap(buffer, offset, length);
}
/**
* The referenced buffer to be used.
*
* @return the referenced buffer to be used.
*/
public MutableDirectBuffer buffer()
{
return buffer;
}
/**
* The offset in the buffer at which the claimed range begins.
*
* @return offset in the buffer at which the range begins.
*/
public int offset()
{
return HEADER_LENGTH;
}
/**
* The length of the claimed range in the buffer.
*
* @return length of the range in the buffer.
*/
public int length()
{
return buffer.capacity() - HEADER_LENGTH;
}
/**
* Get the value of the header type field. The lower 16 bits are valid.
*
* @return the value of the header type field.
* @see io.aeron.protocol.DataHeaderFlyweight
*/
public int headerType()
{
return buffer.getShort(TYPE_FIELD_OFFSET, LITTLE_ENDIAN) & 0xFFFF;
}
/**
* Get the value of the flags field.
*
* @return the value of the header flags field.
* @see io.aeron.protocol.DataHeaderFlyweight
*/
public byte flags()
{
return buffer.getByte(FLAGS_FIELD_OFFSET);
}
/**
* Set the value of the header flags field.
*
* @param flags value to be set in the header.
* @return this for a fluent API.
* @see io.aeron.protocol.DataHeaderFlyweight
*/
public BufferClaim flags(final byte flags)
{
buffer.putByte(FLAGS_FIELD_OFFSET, flags);
return this;
}
/**
* Set the value of the header type field. The lower 16 bits are valid.
*
* @param type value to be set in the header.
* @return this for a fluent API.
* @see io.aeron.protocol.DataHeaderFlyweight
*/
public BufferClaim headerType(final int type)
{
buffer.putShort(TYPE_FIELD_OFFSET, (short)type, LITTLE_ENDIAN);
return this;
}
/**
* Get the value stored in the reserve space at the end of a data frame header.
*
* Note: The value is in {@link ByteOrder#LITTLE_ENDIAN} format.
*
* @return the value stored in the reserve space at the end of a data frame header.
* @see io.aeron.protocol.DataHeaderFlyweight
*/
public long reservedValue()
{
return buffer.getLong(RESERVED_VALUE_OFFSET, LITTLE_ENDIAN);
}
/**
* Write the provided value into the reserved space at the end of the data frame header.
*
* Note: The value will be written in {@link ByteOrder#LITTLE_ENDIAN} format.
*
* @param value to be stored in the reserve space at the end of a data frame header.
* @return this for fluent API semantics.
* @see io.aeron.protocol.DataHeaderFlyweight
*/
public BufferClaim reservedValue(final long value)
{
buffer.putLong(RESERVED_VALUE_OFFSET, value, LITTLE_ENDIAN);
return this;
}
/**
* Put bytes into the claimed buffer space for a message. To write multiple parts then use {@link #buffer()}
* and {@link #offset()}.
*
* @param srcBuffer to copy into the claimed space.
* @param srcIndex in the source buffer from which to copy.
* @param length of the source buffer to copy.
* @return this for a fluent API.
*/
public BufferClaim putBytes(final DirectBuffer srcBuffer, final int srcIndex, final int length)
{
buffer.putBytes(HEADER_LENGTH, srcBuffer, srcIndex, length);
return this;
}
/**
* Commit the message to the log buffer so that is it available to subscribers.
*/
public void commit()
{
int frameLength = buffer.capacity();
if (ByteOrder.nativeOrder() != LITTLE_ENDIAN)
{
frameLength = Integer.reverseBytes(frameLength);
}
buffer.putIntOrdered(FRAME_LENGTH_FIELD_OFFSET, frameLength);
}
/**
* Abort a claim of the message space to the log buffer so that the log can progress by ignoring this claim.
*/
public void abort()
{
int frameLength = buffer.capacity();
if (ByteOrder.nativeOrder() != LITTLE_ENDIAN)
{
frameLength = Integer.reverseBytes(frameLength);
}
buffer.putShort(TYPE_FIELD_OFFSET, (short)HDR_TYPE_PAD, LITTLE_ENDIAN);
buffer.putIntOrdered(FRAME_LENGTH_FIELD_OFFSET, frameLength);
}
}