xerial.core.io.DataProducer.scala Maven / Gradle / Ivy
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//--------------------------------------
//
// DataProducer.scala
// Since: 2012/03/14 11:01
//
//--------------------------------------
package xerial.core.io
import java.io._
import java.nio.CharBuffer
import xerial.core.log.Logger
/**
* Data producer produces data using a thread, and provides input stream to fetch the data.
* To use this trait, implement the [[xerial.core.io.DataProducer.produce]] method, in which
* binary data produced
*
* @author leo
*/
trait DataProducer extends InputStream with DataProducerBase[InputStream, OutputStream] {
protected val pipeIn = new PipedInputStream(8192)
// 8K
protected val pipeOut = new PipedOutputStream(pipeIn)
protected def produceStart: Unit = {
try
produce(pipeOut)
finally {
pipeOut.flush
pipeOut.close
}
}
def produce(out: OutputStream): Unit
def toReader = new InputStreamReader(this)
override def read(): Int = wrap(pipeIn.read)
override def read(b: Array[Byte]): Int = wrap(pipeIn.read(b))
override def read(b: Array[Byte], off: Int, len: Int) = wrap(pipeIn.read(b, off, len))
override def skip(n: Long) = wrap(pipeIn.skip(n))
override def available() = wrap(pipeIn.available())
override def mark(readlimit: Int) = wrap(pipeIn.mark(readlimit))
override def reset() = wrap(pipeIn.reset)
override def markSupported() = wrap(pipeIn.markSupported)
}
/**
* Implementer must invoke startWorker.
* @tparam PipeIn
* @tparam PipeOut
*/
trait DataProducerBase[PipeIn <: Closeable, PipeOut <: Closeable] extends Closeable with Logger {
protected val pipeIn: PipeIn
protected val pipeOut: PipeOut
protected val worker = new Thread(new Runnable {
def run() {
try {
produceStart
}
catch {
case e: InterruptedException => {
// terminated by close
warn("Interrupted while producing data")
}
}
}
})
/**
* Start data production
*/
protected def produceStart: Unit
lazy protected val started: Boolean = {
worker.setDaemon(true)
worker.start()
try {
// Wait until the first data is produced. That also means initialization of classes extending this trait is finished.
// The current thread is awaken by (PipedWriter.write -> PipedReader.recieve -> notifyAll)
Thread.sleep(0)
}
catch {
case e: InterruptedException =>
trace("sleep interrupted")
}
true
}
/**
* Use this method to wrap any read method
* @param f
* @tparam A
* @return
*/
protected def wrap[A](f: => A): A = {
if (started != true)
sys.error("Failed to start the producer")
f
}
override def close {
// No need exists to close the reader explicitly since PipeReader.close resets the buffer
pipeIn.close
pipeOut.close
if (started && worker.isAlive) {
worker.interrupt
}
}
}
/**
* Producer of text data.
*/
trait TextDataProducer extends Reader with DataProducerBase[Reader, Writer] {
protected val pipeIn = new PipedReader
protected val pipeOut = new PrintWriter(new PipedWriter(pipeIn))
protected def produceStart: Unit = {
try {
produce(pipeOut)
}
finally {
pipeOut.flush
pipeOut.close
}
}
def produce(out: PrintWriter): Unit
class LineIterator extends Iterator[String] {
val bufferedReader = new BufferedReader(pipeIn)
var nextLine: String = null
def hasNext = {
if (nextLine == null) {
nextLine = bufferedReader.readLine()
}
nextLine != null
}
def next(): String = {
if (hasNext) {
val line = nextLine
nextLine = null
line
}
else
Iterator.empty.next
}
}
/**
* @deprecated This method has no support for closing the input stream appropriately. Use eachLine or lineIterator instead
* @return
*/
def lines: Iterator[String] = wrap(new LineIterator)
def lineIterator[A](f: Iterator[String] => A): A = {
val lineIt = wrap(new LineIterator)
try
f(lineIt)
finally
close
}
def eachLine[A](f: String => A): Unit = lineIterator(it => it.foreach(line => f(line)))
def readAsString: String = {
try {
val b = new StringBuilder
val buf = new Array[Char](8192)
def loop: Unit = {
val readLen = read(buf)
if (readLen != -1) {
b.appendAll(buf, 0, readLen)
loop
}
}
loop
b.result()
}
finally
close
}
def toInputStream : InputStream = new ReaderInputStream(this)
override def read(target: CharBuffer) = wrap(pipeIn.read(target))
override def read() = wrap(pipeIn.read())
override def read(cbuf: Array[Char]) = wrap(pipeIn.read(cbuf))
override def read(cbuf: Array[Char], offset: Int, len: Int) = wrap(pipeIn.read(cbuf, offset, len))
override def skip(n: Long) = wrap(pipeIn.skip(n))
override def ready() = wrap(pipeIn.ready)
override def markSupported() = wrap(pipeIn.markSupported())
override def mark(readAheadLimit: Int) = wrap(pipeIn.mark(readAheadLimit))
override def reset() = wrap(pipeIn.reset)
}