From 2f5f3754dce85212a71138fd80c2300b73461908 Mon Sep 17 00:00:00 2001 From: Kenny Root Date: Sat, 18 Jul 2015 11:30:18 -0700 Subject: Rename project to sshlib --- .../main/java/com/trilead/ssh2/StreamGobbler.java | 229 +++++++++++++++++++++ 1 file changed, 229 insertions(+) create mode 100644 sshlib/src/main/java/com/trilead/ssh2/StreamGobbler.java (limited to 'sshlib/src/main/java/com/trilead/ssh2/StreamGobbler.java') diff --git a/sshlib/src/main/java/com/trilead/ssh2/StreamGobbler.java b/sshlib/src/main/java/com/trilead/ssh2/StreamGobbler.java new file mode 100644 index 0000000..e93c388 --- /dev/null +++ b/sshlib/src/main/java/com/trilead/ssh2/StreamGobbler.java @@ -0,0 +1,229 @@ + +package com.trilead.ssh2; + +import java.io.IOException; +import java.io.InputStream; + +/** + * A StreamGobbler is an InputStream that uses an internal worker + * thread to constantly consume input from another InputStream. It uses a buffer + * to store the consumed data. The buffer size is automatically adjusted, if needed. + *

+ * This class is sometimes very convenient - if you wrap a session's STDOUT and STDERR + * InputStreams with instances of this class, then you don't have to bother about + * the shared window of STDOUT and STDERR in the low level SSH-2 protocol, + * since all arriving data will be immediatelly consumed by the worker threads. + * Also, as a side effect, the streams will be buffered (e.g., single byte + * read() operations are faster). + *

+ * Other SSH for Java libraries include this functionality by default in + * their STDOUT and STDERR InputStream implementations, however, please be aware + * that this approach has also a downside: + *

+ * If you do not call the StreamGobbler's read() method often enough + * and the peer is constantly sending huge amounts of data, then you will sooner or later + * encounter a low memory situation due to the aggregated data (well, it also depends on the Java heap size). + * Joe Average will like this class anyway - a paranoid programmer would never use such an approach. + *

+ * The term "StreamGobbler" was taken from an article called "When Runtime.exec() won't", + * see http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html. + * + * @author Christian Plattner, plattner@trilead.com + * @version $Id: StreamGobbler.java,v 1.1 2007/10/15 12:49:56 cplattne Exp $ + */ + +public class StreamGobbler extends InputStream +{ + class GobblerThread extends Thread + { + public void run() + { + byte[] buff = new byte[8192]; + + while (true) + { + try + { + int avail = is.read(buff); + + synchronized (synchronizer) + { + if (avail <= 0) + { + isEOF = true; + synchronizer.notifyAll(); + break; + } + + int space_available = buffer.length - write_pos; + + if (space_available < avail) + { + /* compact/resize buffer */ + + int unread_size = write_pos - read_pos; + int need_space = unread_size + avail; + + byte[] new_buffer = buffer; + + if (need_space > buffer.length) + { + int inc = need_space / 3; + inc = (inc < 256) ? 256 : inc; + inc = (inc > 8192) ? 8192 : inc; + new_buffer = new byte[need_space + inc]; + } + + if (unread_size > 0) + System.arraycopy(buffer, read_pos, new_buffer, 0, unread_size); + + buffer = new_buffer; + + read_pos = 0; + write_pos = unread_size; + } + + System.arraycopy(buff, 0, buffer, write_pos, avail); + write_pos += avail; + + synchronizer.notifyAll(); + } + } + catch (IOException e) + { + synchronized (synchronizer) + { + exception = e; + synchronizer.notifyAll(); + break; + } + } + } + } + } + + private InputStream is; + private GobblerThread t; + + private Object synchronizer = new Object(); + + private boolean isEOF = false; + private boolean isClosed = false; + private IOException exception = null; + + private byte[] buffer = new byte[2048]; + private int read_pos = 0; + private int write_pos = 0; + + public StreamGobbler(InputStream is) + { + this.is = is; + t = new GobblerThread(); + t.setDaemon(true); + t.start(); + } + + public int read() throws IOException + { + synchronized (synchronizer) + { + if (isClosed) + throw new IOException("This StreamGobbler is closed."); + + while (read_pos == write_pos) + { + if (exception != null) + throw exception; + + if (isEOF) + return -1; + + try + { + synchronizer.wait(); + } + catch (InterruptedException e) + { + } + } + + int b = buffer[read_pos++] & 0xff; + + return b; + } + } + + public int available() throws IOException + { + synchronized (synchronizer) + { + if (isClosed) + throw new IOException("This StreamGobbler is closed."); + + return write_pos - read_pos; + } + } + + public int read(byte[] b) throws IOException + { + return read(b, 0, b.length); + } + + public void close() throws IOException + { + synchronized (synchronizer) + { + if (isClosed) + return; + isClosed = true; + isEOF = true; + synchronizer.notifyAll(); + is.close(); + } + } + + public int read(byte[] b, int off, int len) throws IOException + { + if (b == null) + throw new NullPointerException(); + + if ((off < 0) || (len < 0) || ((off + len) > b.length) || ((off + len) < 0) || (off > b.length)) + throw new IndexOutOfBoundsException(); + + if (len == 0) + return 0; + + synchronized (synchronizer) + { + if (isClosed) + throw new IOException("This StreamGobbler is closed."); + + while (read_pos == write_pos) + { + if (exception != null) + throw exception; + + if (isEOF) + return -1; + + try + { + synchronizer.wait(); + } + catch (InterruptedException e) + { + } + } + + int avail = write_pos - read_pos; + + avail = (avail > len) ? len : avail; + + System.arraycopy(buffer, read_pos, b, off, avail); + + read_pos += avail; + + return avail; + } + } +} -- cgit v1.2.3