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| 1 | /* | ||
| 2 | * Copyright (c) 1994, 2006, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.io; | ||
| 27 | |||
| 28 | import java.io.InputStream; | ||
| 29 | import java.util.Enumeration; | ||
| 30 | import java.util.Vector; | ||
| 31 | |||
| 32 | /** | ||
| 33 | * A <code>SequenceInputStream</code> represents | ||
| 34 | * the logical concatenation of other input | ||
| 35 | * streams. It starts out with an ordered | ||
| 36 | * collection of input streams and reads from | ||
| 37 | * the first one until end of file is reached, | ||
| 38 | * whereupon it reads from the second one, | ||
| 39 | * and so on, until end of file is reached | ||
| 40 | * on the last of the contained input streams. | ||
| 41 | * | ||
| 42 | * @author Author van Hoff | ||
| 43 | * @since JDK1.0 | ||
| 44 | */ | ||
| 45 | public | ||
| 46 | class SequenceInputStream extends InputStream { | ||
| 47 | Enumeration e; | ||
| 48 | InputStream in; | ||
| 49 | |||
| 50 | /** | ||
| 51 | * Initializes a newly created <code>SequenceInputStream</code> | ||
| 52 | * by remembering the argument, which must | ||
| 53 | * be an <code>Enumeration</code> that produces | ||
| 54 | * objects whose run-time type is <code>InputStream</code>. | ||
| 55 | * The input streams that are produced by | ||
| 56 | * the enumeration will be read, in order, | ||
| 57 | * to provide the bytes to be read from this | ||
| 58 | * <code>SequenceInputStream</code>. After | ||
| 59 | * each input stream from the enumeration | ||
| 60 | * is exhausted, it is closed by calling its | ||
| 61 | * <code>close</code> method. | ||
| 62 | * | ||
| 63 | * @param e an enumeration of input streams. | ||
| 64 | * @see java.util.Enumeration | ||
| 65 | */ | ||
| 66 | public SequenceInputStream(Enumeration<? extends InputStream> e) { | ||
| 67 | this.e = e; | ||
| 68 | try { | ||
| 69 | nextStream(); | ||
| 70 | } catch (IOException ex) { | ||
| 71 | // This should never happen | ||
| 72 | throw new Error("panic"); | ||
| 73 | } | ||
| 74 | } | ||
| 75 | |||
| 76 | /** | ||
| 77 | * Initializes a newly | ||
| 78 | * created <code>SequenceInputStream</code> | ||
| 79 | * by remembering the two arguments, which | ||
| 80 | * will be read in order, first <code>s1</code> | ||
| 81 | * and then <code>s2</code>, to provide the | ||
| 82 | * bytes to be read from this <code>SequenceInputStream</code>. | ||
| 83 | * | ||
| 84 | * @param s1 the first input stream to read. | ||
| 85 | * @param s2 the second input stream to read. | ||
| 86 | */ | ||
| 87 | public SequenceInputStream(InputStream s1, InputStream s2) { | ||
| 88 | Vector v = new Vector(2); | ||
| 89 | |||
| 90 | v.addElement(s1); | ||
| 91 | v.addElement(s2); | ||
| 92 | e = v.elements(); | ||
| 93 | try { | ||
| 94 | nextStream(); | ||
| 95 | } catch (IOException ex) { | ||
| 96 | // This should never happen | ||
| 97 | throw new Error("panic"); | ||
| 98 | } | ||
| 99 | } | ||
| 100 | |||
| 101 | /** | ||
| 102 | * Continues reading in the next stream if an EOF is reached. | ||
| 103 | */ | ||
| 104 | final void nextStream() throws IOException { | ||
| 105 | if (in != null) { | ||
| 106 | in.close(); | ||
| 107 | } | ||
| 108 | |||
| 109 | if (e.hasMoreElements()) { | ||
| 110 | in = (InputStream) e.nextElement(); | ||
| 111 | if (in == null) | ||
| 112 | throw new NullPointerException(); | ||
| 113 | } | ||
| 114 | else in = null; | ||
| 115 | |||
| 116 | } | ||
| 117 | |||
| 118 | /** | ||
| 119 | * Returns an estimate of the number of bytes that can be read (or | ||
| 120 | * skipped over) from the current underlying input stream without | ||
| 121 | * blocking by the next invocation of a method for the current | ||
| 122 | * underlying input stream. The next invocation might be | ||
| 123 | * the same thread or another thread. A single read or skip of this | ||
| 124 | * many bytes will not block, but may read or skip fewer bytes. | ||
| 125 | * <p> | ||
| 126 | * This method simply calls {@code available} of the current underlying | ||
| 127 | * input stream and returns the result. | ||
| 128 | * | ||
| 129 | * @return an estimate of the number of bytes that can be read (or | ||
| 130 | * skipped over) from the current underlying input stream | ||
| 131 | * without blocking or {@code 0} if this input stream | ||
| 132 | * has been closed by invoking its {@link #close()} method | ||
| 133 | * @exception IOException if an I/O error occurs. | ||
| 134 | * | ||
| 135 | * @since JDK1.1 | ||
| 136 | */ | ||
| 137 | public int available() throws IOException { | ||
| 138 | if(in == null) { | ||
| 139 | return 0; // no way to signal EOF from available() | ||
| 140 | } | ||
| 141 | return in.available(); | ||
| 142 | } | ||
| 143 | |||
| 144 | /** | ||
| 145 | * Reads the next byte of data from this input stream. The byte is | ||
| 146 | * returned as an <code>int</code> in the range <code>0</code> to | ||
| 147 | * <code>255</code>. If no byte is available because the end of the | ||
| 148 | * stream has been reached, the value <code>-1</code> is returned. | ||
| 149 | * This method blocks until input data is available, the end of the | ||
| 150 | * stream is detected, or an exception is thrown. | ||
| 151 | * <p> | ||
| 152 | * This method | ||
| 153 | * tries to read one character from the current substream. If it | ||
| 154 | * reaches the end of the stream, it calls the <code>close</code> | ||
| 155 | * method of the current substream and begins reading from the next | ||
| 156 | * substream. | ||
| 157 | * | ||
| 158 | * @return the next byte of data, or <code>-1</code> if the end of the | ||
| 159 | * stream is reached. | ||
| 160 | * @exception IOException if an I/O error occurs. | ||
| 161 | */ | ||
| 162 | public int read() throws IOException { | ||
| 163 | if (in == null) { | ||
| 164 | return -1; | ||
| 165 | } | ||
| 166 | int c = in.read(); | ||
| 167 | if (c == -1) { | ||
| 168 | nextStream(); | ||
| 169 | return read(); | ||
| 170 | } | ||
| 171 | return c; | ||
| 172 | } | ||
| 173 | |||
| 174 | /** | ||
| 175 | * Reads up to <code>len</code> bytes of data from this input stream | ||
| 176 | * into an array of bytes. If <code>len</code> is not zero, the method | ||
| 177 | * blocks until at least 1 byte of input is available; otherwise, no | ||
| 178 | * bytes are read and <code>0</code> is returned. | ||
| 179 | * <p> | ||
| 180 | * The <code>read</code> method of <code>SequenceInputStream</code> | ||
| 181 | * tries to read the data from the current substream. If it fails to | ||
| 182 | * read any characters because the substream has reached the end of | ||
| 183 | * the stream, it calls the <code>close</code> method of the current | ||
| 184 | * substream and begins reading from the next substream. | ||
| 185 | * | ||
| 186 | * @param b the buffer into which the data is read. | ||
| 187 | * @param off the start offset in array <code>b</code> | ||
| 188 | * at which the data is written. | ||
| 189 | * @param len the maximum number of bytes read. | ||
| 190 | * @return int the number of bytes read. | ||
| 191 | * @exception NullPointerException If <code>b</code> is <code>null</code>. | ||
| 192 | * @exception IndexOutOfBoundsException If <code>off</code> is negative, | ||
| 193 | * <code>len</code> is negative, or <code>len</code> is greater than | ||
| 194 | * <code>b.length - off</code> | ||
| 195 | * @exception IOException if an I/O error occurs. | ||
| 196 | */ | ||
| 197 | public int read(byte b[], int off, int len) throws IOException { | ||
| 198 | if (in == null) { | ||
| 199 | return -1; | ||
| 200 | } else if (b == null) { | ||
| 201 | throw new NullPointerException(); | ||
| 202 | } else if (off < 0 || len < 0 || len > b.length - off) { | ||
| 203 | throw new IndexOutOfBoundsException(); | ||
| 204 | } else if (len == 0) { | ||
| 205 | return 0; | ||
| 206 | } | ||
| 207 | |||
| 208 | int n = in.read(b, off, len); | ||
| 209 | if (n <= 0) { | ||
| 210 | nextStream(); | ||
| 211 | return read(b, off, len); | ||
| 212 | } | ||
| 213 | return n; | ||
| 214 | } | ||
| 215 | |||
| 216 | /** | ||
| 217 | * Closes this input stream and releases any system resources | ||
| 218 | * associated with the stream. | ||
| 219 | * A closed <code>SequenceInputStream</code> | ||
| 220 | * cannot perform input operations and cannot | ||
| 221 | * be reopened. | ||
| 222 | * <p> | ||
| 223 | * If this stream was created | ||
| 224 | * from an enumeration, all remaining elements | ||
| 225 | * are requested from the enumeration and closed | ||
| 226 | * before the <code>close</code> method returns. | ||
| 227 | * | ||
| 228 | * @exception IOException if an I/O error occurs. | ||
| 229 | */ | ||
| 230 | public void close() throws IOException { | ||
| 231 | do { | ||
| 232 | nextStream(); | ||
| 233 | } while (in != null); | ||
| 234 | } | ||
| 235 | } | ||