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package org.glassfish.jersey.internal.util.collection;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;

import org.glassfish.jersey.internal.LocalizationMessages;

/**
 * An {@link java.io.InputStream} backed by a queue of {@link java.nio.ByteBuffer byte buffers}
 * to be read.
 * 

* This input stream serves as a bridging inbound I/O component between a blocking upper I/O layer * and an underlying non-blocking I/O layer. In addition to the blocking {@code InputStream.read} operations, * this input stream provides the non-blocking {@code tryRead} counterparts. *

* * @author Marek Potociar (marek.potociar at oracle.com) */ public final class ByteBufferInputStream extends NonBlockingInputStream { /** * Constant buffer indicating EOF. */ private static final ByteBuffer EOF = ByteBuffer.wrap(new byte[]{}); /** * Read-side EOF flag. Does not have to be volatile, it is transient and only accessed from the reader thread. */ private boolean eof = false; /** * Currently read byte buffer. */ private ByteBuffer current; /** * Queue of byte buffers to be read. */ private final BlockingQueue buffers; /** * Content represents the buffer queue status. * * null = open, POISON_PILL = closed, Throwable = closed with error */ private final AtomicReference queueStatus = new AtomicReference(null); /** * Closed flag. */ private final AtomicBoolean closed = new AtomicBoolean(false); /** * Create a new input stream that is backed by a a queue of {@link java.nio.ByteBuffer byte buffers} * to be read. */ public ByteBufferInputStream() { this.buffers = DataStructures.createLinkedTransferQueue(); this.current = null; } private boolean fetchChunk(final boolean block) throws InterruptedException { if (eof) { return false; } // Read until no buffers available (poll returned null) // or until a non-empty buffer or EOF is reached. do { if (closed.get()) { current = EOF; break; } current = (block) ? buffers.take() : buffers.poll(); } while (current != null && current != EOF && !current.hasRemaining()); eof = current == EOF; return !eof; } private void checkNotClosed() throws IOException { if (closed.get()) { throw new IOException(LocalizationMessages.INPUT_STREAM_CLOSED()); } } private void checkThrowable() throws IOException { Object o = queueStatus.get(); if (o != null && o != EOF) { // should be faster than instanceof // if not null or EOF, then it must be Throwable if (queueStatus.compareAndSet(o, EOF)) { // clear throwable flag and throw exception try { throw new IOException((Throwable) o); } finally { close(); } } } } @Override public int available() throws IOException { if (eof || closed.get()) { checkThrowable(); return 0; } int available = 0; if (current != null && current.hasRemaining()) { available = current.remaining(); } for (ByteBuffer buffer : buffers) { if (buffer == EOF) { break; } available += buffer.remaining(); } checkThrowable(); return closed.get() ? 0 : available; } @Override public int read() throws IOException { if (eof) { checkThrowable(); checkNotClosed(); return -1; } final int c; if (current != null && current.hasRemaining()) { c = current.get(); } else { try { // let's block until next non-empty chunk or EOF c = fetchChunk(true) ? current.get() : -1; } catch (InterruptedException e) { Thread.currentThread().interrupt(); throw new IOException(e); } } checkThrowable(); checkNotClosed(); return c; } @Override public int tryRead() throws IOException { checkThrowable(); checkNotClosed(); if (eof) { return -1; } if (current != null && current.hasRemaining()) { return current.get(); } try { // try to fetch, but don't block && check if something has been fetched if (fetchChunk(false) && current != null) { return current.get(); } } catch (InterruptedException e) { Thread.currentThread().interrupt(); } return (eof) ? -1 : NOTHING; } @Override public int tryRead(byte b[]) throws IOException { return tryRead(b, 0, b.length); } @Override public int tryRead(byte b[], int off, int len) throws IOException { checkThrowable(); checkNotClosed(); if (b == null) { throw new NullPointerException(); } else if (off < 0 || len < 0 || len > b.length - off) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return 0; } if (eof) { return -1; } int i = 0; while (i < len) { if (current != null && current.hasRemaining()) { final int available = current.remaining(); if (available < len - i) { current.get(b, off + i, available); i += available; } else { current.get(b, off + i, len - i); return len; } } else try { if (!fetchChunk(false) || current == null) { break; // eof or no data } } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } return i; } @Override public void close() throws IOException { if (closed.compareAndSet(false, true)) { closeQueue(); // we can now safely clear the queue - any blocking read waiting for a buffer // has been resumed by the EOF buffer buffers.clear(); } checkThrowable(); } /** * Put the {@code ByteBuffer} to the internal queue to be available for reading from the stream. * *

* If the sink is open, the method {@link BlockingQueue#put(Object) puts the buffer} into an internal * byte buffer read queue , waiting if necessary for space to become available. Then the method returns * {@code true} to indicate the buffer has been successfully queued. In case the internal read queue has been * {@link #closeQueue() closed} already, the method simply returns {@code false} without registering * the buffer in the closed queue. *

* * @param src the source buffer to be registered in the byte buffer read queue. * @return {@code true} if the byte buffer has been successfully put in the read queue, * {@code false} if the read queue has been closed. * @throws InterruptedException in case the put operation has been interrupted. */ public boolean put(ByteBuffer src) throws InterruptedException { if (queueStatus.get() == null) { buffers.put(src); return true; } return false; } /** * Closes the byte buffer sink of this input stream to indicate that writing to the stream * has been finished. *

* If the sink has already been closed then this method returns immediately. Otherwise the * sink is marked as closed and no more data can be written to it. *

*/ public void closeQueue() { if (queueStatus.compareAndSet(null, EOF)) { try { buffers.put(EOF); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } /** * Closes the byte buffer sink of this input stream to indicate that writing to the stream * has been finished due to a throwable. * * The throwable set by this method will be propagated to the reader thread when a new attempt * to read bytes is made. *

* If the sink has already been closed then this method only sets the throwable in the stream and * then returns immediately. Otherwise the sink is also marked as closed and no more data can be * written to it. *

* * @param throwable throwable that is set in the stream. It will be thrown by the stream in case * an attempt to read more data or check available bytes is made. */ public void closeQueue(Throwable throwable) { if (queueStatus.compareAndSet(null, throwable)) { try { buffers.put(EOF); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } } } }