| /* |
| * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code 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 |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.io; |
| |
| import java.io.InputStream; |
| import java.util.Enumeration; |
| import java.util.Vector; |
| |
| /** |
| * A <code>SequenceInputStream</code> represents |
| * the logical concatenation of other input |
| * streams. It starts out with an ordered |
| * collection of input streams and reads from |
| * the first one until end of file is reached, |
| * whereupon it reads from the second one, |
| * and so on, until end of file is reached |
| * on the last of the contained input streams. |
| * |
| * @author Author van Hoff |
| * @since JDK1.0 |
| */ |
| public |
| class SequenceInputStream extends InputStream { |
| Enumeration<? extends InputStream> e; |
| InputStream in; |
| |
| /** |
| * Initializes a newly created <code>SequenceInputStream</code> |
| * by remembering the argument, which must |
| * be an <code>Enumeration</code> that produces |
| * objects whose run-time type is <code>InputStream</code>. |
| * The input streams that are produced by |
| * the enumeration will be read, in order, |
| * to provide the bytes to be read from this |
| * <code>SequenceInputStream</code>. After |
| * each input stream from the enumeration |
| * is exhausted, it is closed by calling its |
| * <code>close</code> method. |
| * |
| * @param e an enumeration of input streams. |
| * @see java.util.Enumeration |
| */ |
| public SequenceInputStream(Enumeration<? extends InputStream> e) { |
| this.e = e; |
| try { |
| nextStream(); |
| } catch (IOException ex) { |
| // This should never happen |
| throw new Error("panic"); |
| } |
| } |
| |
| /** |
| * Initializes a newly |
| * created <code>SequenceInputStream</code> |
| * by remembering the two arguments, which |
| * will be read in order, first <code>s1</code> |
| * and then <code>s2</code>, to provide the |
| * bytes to be read from this <code>SequenceInputStream</code>. |
| * |
| * @param s1 the first input stream to read. |
| * @param s2 the second input stream to read. |
| */ |
| public SequenceInputStream(InputStream s1, InputStream s2) { |
| Vector<InputStream> v = new Vector<>(2); |
| |
| v.addElement(s1); |
| v.addElement(s2); |
| e = v.elements(); |
| try { |
| nextStream(); |
| } catch (IOException ex) { |
| // This should never happen |
| throw new Error("panic"); |
| } |
| } |
| |
| /** |
| * Continues reading in the next stream if an EOF is reached. |
| */ |
| final void nextStream() throws IOException { |
| if (in != null) { |
| in.close(); |
| } |
| |
| if (e.hasMoreElements()) { |
| in = (InputStream) e.nextElement(); |
| if (in == null) |
| throw new NullPointerException(); |
| } |
| else in = null; |
| |
| } |
| |
| /** |
| * Returns an estimate of the number of bytes that can be read (or |
| * skipped over) from the current underlying input stream without |
| * blocking by the next invocation of a method for the current |
| * underlying input stream. The next invocation might be |
| * the same thread or another thread. A single read or skip of this |
| * many bytes will not block, but may read or skip fewer bytes. |
| * <p> |
| * This method simply calls {@code available} of the current underlying |
| * input stream and returns the result. |
| * |
| * @return an estimate of the number of bytes that can be read (or |
| * skipped over) from the current underlying input stream |
| * without blocking or {@code 0} if this input stream |
| * has been closed by invoking its {@link #close()} method |
| * @exception IOException if an I/O error occurs. |
| * |
| * @since JDK1.1 |
| */ |
| public int available() throws IOException { |
| if (in == null) { |
| return 0; // no way to signal EOF from available() |
| } |
| return in.available(); |
| } |
| |
| /** |
| * Reads the next byte of data from this input stream. The byte is |
| * returned as an <code>int</code> in the range <code>0</code> to |
| * <code>255</code>. If no byte is available because the end of the |
| * stream has been reached, the value <code>-1</code> is returned. |
| * This method blocks until input data is available, the end of the |
| * stream is detected, or an exception is thrown. |
| * <p> |
| * This method |
| * tries to read one character from the current substream. If it |
| * reaches the end of the stream, it calls the <code>close</code> |
| * method of the current substream and begins reading from the next |
| * substream. |
| * |
| * @return the next byte of data, or <code>-1</code> if the end of the |
| * stream is reached. |
| * @exception IOException if an I/O error occurs. |
| */ |
| public int read() throws IOException { |
| while (in != null) { |
| int c = in.read(); |
| if (c != -1) { |
| return c; |
| } |
| nextStream(); |
| } |
| return -1; |
| } |
| |
| /** |
| * Reads up to <code>len</code> bytes of data from this input stream |
| * into an array of bytes. If <code>len</code> is not zero, the method |
| * blocks until at least 1 byte of input is available; otherwise, no |
| * bytes are read and <code>0</code> is returned. |
| * <p> |
| * The <code>read</code> method of <code>SequenceInputStream</code> |
| * tries to read the data from the current substream. If it fails to |
| * read any characters because the substream has reached the end of |
| * the stream, it calls the <code>close</code> method of the current |
| * substream and begins reading from the next substream. |
| * |
| * @param b the buffer into which the data is read. |
| * @param off the start offset in array <code>b</code> |
| * at which the data is written. |
| * @param len the maximum number of bytes read. |
| * @return int the number of bytes read. |
| * @exception NullPointerException If <code>b</code> is <code>null</code>. |
| * @exception IndexOutOfBoundsException If <code>off</code> is negative, |
| * <code>len</code> is negative, or <code>len</code> is greater than |
| * <code>b.length - off</code> |
| * @exception IOException if an I/O error occurs. |
| */ |
| public int read(byte b[], int off, int len) throws IOException { |
| if (in == null) { |
| return -1; |
| } else 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; |
| } |
| do { |
| int n = in.read(b, off, len); |
| if (n > 0) { |
| return n; |
| } |
| nextStream(); |
| } while (in != null); |
| return -1; |
| } |
| |
| /** |
| * Closes this input stream and releases any system resources |
| * associated with the stream. |
| * A closed <code>SequenceInputStream</code> |
| * cannot perform input operations and cannot |
| * be reopened. |
| * <p> |
| * If this stream was created |
| * from an enumeration, all remaining elements |
| * are requested from the enumeration and closed |
| * before the <code>close</code> method returns. |
| * |
| * @exception IOException if an I/O error occurs. |
| */ |
| public void close() throws IOException { |
| do { |
| nextStream(); |
| } while (in != null); |
| } |
| } |