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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/io/SequenceInputStream.java
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+/* SequenceInputStream.java -- Reads multiple input streams in sequence
+ Copyright (C) 1998, 1999, 2001, 2004, 2005 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.io;
+
+import java.util.Enumeration;
+
+/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
+ * "The Java Language Specification", ISBN 0-201-63451-1
+ * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
+ * Status: Believed complete and correct.
+ */
+
+/**
+ * This class merges a sequence of multiple <code>InputStream</code>'s in
+ * order to form a single logical stream that can be read by applications
+ * that expect only one stream.
+ * <p>
+ * The streams passed to the constructor method are read in order until
+ * they return -1 to indicate they are at end of stream. When a stream
+ * reports end of stream, it is closed, then the next stream is read.
+ * When the last stream is closed, the next attempt to read from this
+ * stream will return a -1 to indicate it is at end of stream.
+ * <p>
+ * If this stream is closed prior to all subordinate streams being read
+ * to completion, all subordinate streams are closed.
+ *
+ * @author Aaron M. Renn (arenn@urbanophile.com)
+ * @author Warren Levy (warrenl@cygnus.com)
+ */
+public class SequenceInputStream extends InputStream
+{
+ /** The handle for the current input stream. */
+ private InputStream in;
+
+ /** Secondary input stream; not used if constructed w/ enumeration. */
+ private InputStream in2;
+
+ /**
+ * The enumeration handle; not used if constructed w/ 2 explicit
+ * input streams.
+ */
+ private Enumeration<? extends InputStream> e;
+
+ /**
+ * This method creates a new <code>SequenceInputStream</code> that obtains
+ * its list of subordinate <code>InputStream</code>s from the specified
+ * <code>Enumeration</code>
+ *
+ * @param e An <code>Enumeration</code> that will return a list of
+ * <code>InputStream</code>s to read in sequence
+ */
+ public SequenceInputStream(Enumeration<? extends InputStream> e)
+ {
+ this.e = e;
+ in = e.nextElement();
+ in2 = null;
+ }
+
+ /**
+ * This method creates a new <code>SequenceInputStream</code> that will read
+ * the two specified subordinate <code>InputStream</code>s in sequence.
+ *
+ * @param s1 The first <code>InputStream</code> to read
+ * @param s2 The second <code>InputStream</code> to read
+ */
+ public SequenceInputStream(InputStream s1, InputStream s2)
+ {
+ in = s1;
+ in2 = s2;
+ }
+
+ /**
+ * This method returns the number of bytes than can be read from the
+ * currently being read subordinate stream before that stream could
+ * block. Note that it is possible more bytes than this can actually
+ * be read without the stream blocking. If a 0 is returned, then the
+ * stream could block on the very next read.
+ *
+ * @return The number of bytes that can be read before blocking could occur
+ *
+ * @exception IOException If an error occurs
+ */
+ public int available() throws IOException
+ {
+ if (in == null)
+ return 0;
+
+ return in.available();
+ }
+
+ /**
+ * Closes this stream. This will cause any remaining unclosed subordinate
+ * <code>InputStream</code>'s to be closed as well. Subsequent attempts to
+ * read from this stream may cause an exception.
+ *
+ * @exception IOException If an error occurs
+ */
+ public void close() throws IOException
+ {
+ while (in != null)
+ {
+ in.close();
+ in = getNextStream ();
+ }
+ }
+
+ /**
+ * This method reads an unsigned byte from the input stream and returns it
+ * as an int in the range of 0-255. This method also will return -1 if
+ * the end of the stream has been reached. This will only happen when
+ * all of the subordinate streams have been read.
+ * <p>
+ * This method will block until the byte can be read.
+ *
+ * @return The byte read, or -1 if end of stream
+ *
+ * @exception IOException If an error occurs
+ */
+ public int read() throws IOException
+ {
+ int ch = -1;
+
+ while (in != null && (ch = in.read()) < 0)
+ {
+ in.close();
+ in = getNextStream();
+ }
+
+ return ch;
+ }
+
+ /**
+ * This method reads bytes from a stream and stores them into a caller
+ * supplied buffer. It starts storing the data at index <code>offset</code>
+ * into the buffer and attempts to read <code>len</code> bytes. This method
+ * can return before reading the number of bytes requested. The actual number
+ * of bytes read is returned as an int. A -1 is returend to indicate the
+ * end of the stream. This will only happen when all of the subordinate
+ * streams have been read.
+ * <p>
+ * This method will block until at least one byte can be read.
+ *
+ * @param b The array into which bytes read should be stored
+ * @param off The offset into the array to start storing bytes
+ * @param len The requested number of bytes to read
+ *
+ * @return The actual number of bytes read, or -1 if end of stream
+ *
+ * @exception IOException If an error occurs
+ */
+ public int read(byte[] b, int off, int len) throws IOException
+ {
+ int ch = -1;
+
+ // The validity of the parameters will be checked by in.read so
+ // don't bother doing it here.
+ while (in != null && (ch = in.read(b, off, len)) < 0)
+ {
+ in.close();
+ in = getNextStream();
+ }
+
+ return ch;
+ }
+
+ /**
+ * This private method is used to get the next <code>InputStream</code> to
+ * read from. Returns null when no more streams are available.
+ */
+ private InputStream getNextStream()
+ {
+ InputStream nextIn = null;
+
+ if (e != null)
+ {
+ if (e.hasMoreElements())
+ nextIn = e.nextElement();
+ }
+ else if (in2 != null)
+ {
+ nextIn = in2;
+ in2 = null;
+ }
+
+ return nextIn;
+ }
+}