kafka.message.MessageSet.scala Maven / Gradle / Ivy
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/**
* 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.
*/
package kafka.message
import java.nio._
import java.nio.channels._
/**
* Message set helper functions
*/
object MessageSet {
val MessageSizeLength = 4
val OffsetLength = 8
val LogOverhead = MessageSizeLength + OffsetLength
val Empty = new ByteBufferMessageSet(ByteBuffer.allocate(0))
/**
* The size of a message set containing the given messages
*/
def messageSetSize(messages: Iterable[Message]): Int =
messages.foldLeft(0)(_ + entrySize(_))
/**
* The size of a list of messages
*/
def messageSetSize(messages: java.util.List[Message]): Int = {
var size = 0
val iter = messages.iterator
while(iter.hasNext) {
val message = iter.next.asInstanceOf[Message]
size += entrySize(message)
}
size
}
/**
* The size of a size-delimited entry in a message set
*/
def entrySize(message: Message): Int = LogOverhead + message.size
}
/**
* A set of messages with offsets. A message set has a fixed serialized form, though the container
* for the bytes could be either in-memory or on disk. The format of each message is
* as follows:
* 8 byte message offset number
* 4 byte size containing an integer N
* N message bytes as described in the Message class
*/
abstract class MessageSet extends Iterable[MessageAndOffset] {
/** Write the messages in this set to the given channel starting at the given offset byte.
* Less than the complete amount may be written, but no more than maxSize can be. The number
* of bytes written is returned */
def writeTo(channel: GatheringByteChannel, offset: Long, maxSize: Int): Int
/**
* Provides an iterator over the message/offset pairs in this set
*/
def iterator: Iterator[MessageAndOffset]
/**
* Gives the total size of this message set in bytes
*/
def sizeInBytes: Int
/**
* Print this message set's contents. If the message set has more than 100 messages, just
* print the first 100.
*/
override def toString: String = {
val builder = new StringBuilder()
builder.append(getClass.getSimpleName + "(")
val iter = this.iterator
var i = 0
while(iter.hasNext && i < 100) {
val message = iter.next
builder.append(message)
if(iter.hasNext)
builder.append(", ")
i += 1
}
if(iter.hasNext)
builder.append("...")
builder.append(")")
builder.toString
}
}