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annotate src/goodjava/io/BufferedInputStream.java @ 1480:1f41e5921090
input buffering
| author | Franklin Schmidt <fschmidt@gmail.com> |
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| date | Fri, 24 Apr 2020 14:32:20 -0600 |
| parents | bd13aaeaf6d4 |
| children | 97740900c820 |
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1 /* |
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2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved. |
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3 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
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4 */ |
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5 |
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6 package goodjava.io; |
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7 |
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8 import java.io.InputStream; |
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9 import java.io.FilterInputStream; |
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10 import java.io.IOException; |
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11 |
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12 /** |
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13 * A <code>BufferedInputStream</code> adds |
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14 * functionality to another input stream-namely, |
| 1480 | 15 * the ability to buffer the input. When the <code>BufferedInputStream</code> |
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16 * is created, an internal buffer array is |
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17 * created. As bytes from the stream are read |
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18 * or skipped, the internal buffer is refilled |
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19 * as necessary from the contained input stream, |
| 1480 | 20 * many bytes at a time. |
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21 * |
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22 * @author Arthur van Hoff |
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23 * @since JDK1.0 |
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24 */ |
| 1480 | 25 public final class BufferedInputStream extends FilterInputStream { |
| 1479 | 26 private static int DEFAULT_BUFFER_SIZE = 8192; |
| 1480 | 27 private final byte buf[]; |
| 28 private boolean isClosed = false; | |
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29 |
| 1479 | 30 /** |
| 31 * The index one greater than the index of the last valid byte in | |
| 32 * the buffer. | |
| 33 * This value is always | |
| 34 * in the range <code>0</code> through <code>buf.length</code>; | |
| 35 * elements <code>buf[0]</code> through <code>buf[count-1] | |
| 36 * </code>contain buffered input data obtained | |
| 1480 | 37 * from the underlying input stream. |
| 1479 | 38 */ |
| 1480 | 39 private int count; |
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40 |
| 1479 | 41 /** |
| 42 * The current position in the buffer. This is the index of the next | |
| 43 * character to be read from the <code>buf</code> array. | |
| 44 * <p> | |
| 45 * This value is always in the range <code>0</code> | |
| 46 * through <code>count</code>. If it is less | |
| 47 * than <code>count</code>, then <code>buf[pos]</code> | |
| 48 * is the next byte to be supplied as input; | |
| 49 * if it is equal to <code>count</code>, then | |
| 50 * the next <code>read</code> or <code>skip</code> | |
| 51 * operation will require more bytes to be | |
| 52 * read from the contained input stream. | |
| 53 * | |
| 54 * @see java.io.BufferedInputStream#buf | |
| 55 */ | |
| 1480 | 56 private int pos; |
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57 |
| 1480 | 58 private void checkClosed() throws IOException { |
| 59 if (isClosed) | |
| 1479 | 60 throw new IOException("Stream closed"); |
| 61 } | |
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62 |
| 1479 | 63 /** |
| 64 * Creates a <code>BufferedInputStream</code> | |
| 65 * and saves its argument, the input stream | |
| 66 * <code>in</code>, for later use. An internal | |
| 67 * buffer array is created and stored in <code>buf</code>. | |
| 68 * | |
| 69 * @param in the underlying input stream. | |
| 70 */ | |
| 71 public BufferedInputStream(InputStream in) { | |
| 72 this(in, DEFAULT_BUFFER_SIZE); | |
| 73 } | |
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74 |
| 1479 | 75 /** |
| 76 * Creates a <code>BufferedInputStream</code> | |
| 77 * with the specified buffer size, | |
| 78 * and saves its argument, the input stream | |
| 79 * <code>in</code>, for later use. An internal | |
| 80 * buffer array of length <code>size</code> | |
| 81 * is created and stored in <code>buf</code>. | |
| 82 * | |
| 83 * @param in the underlying input stream. | |
| 84 * @param size the buffer size. | |
| 85 */ | |
| 86 public BufferedInputStream(InputStream in, int size) { | |
| 87 super(in); | |
| 88 buf = new byte[size]; | |
| 89 } | |
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90 |
| 1479 | 91 /** |
| 1480 | 92 * Fills the buffer with more data. |
| 1479 | 93 * Assumes that it is being called by a synchronized method. |
| 94 * This method also assumes that all data has already been read in, | |
| 95 * hence pos > count. | |
| 96 */ | |
| 97 private void fill() throws IOException { | |
| 1480 | 98 pos = 0; |
| 99 count = 0; | |
| 100 int n = super.read(buf, 0, buf.length); | |
| 1479 | 101 if (n > 0) |
| 1480 | 102 count = n; |
| 1479 | 103 } |
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104 |
| 1479 | 105 /** |
| 106 * See | |
| 107 * the general contract of the <code>read</code> | |
| 108 * method of <code>InputStream</code>. | |
| 109 * | |
| 110 * @return the next byte of data, or <code>-1</code> if the end of the | |
| 111 * stream is reached. | |
| 112 * @exception IOException if this input stream has been closed by | |
| 113 * invoking its {@link #close()} method, | |
| 114 * or an I/O error occurs. | |
| 115 * @see java.io.FilterInputStream#in | |
| 116 */ | |
| 117 public synchronized int read() throws IOException { | |
| 1480 | 118 checkClosed(); |
| 1479 | 119 if (pos >= count) { |
| 120 fill(); | |
| 121 if (pos >= count) | |
| 122 return -1; | |
| 123 } | |
| 1480 | 124 return buf[pos++] & 0xff; |
| 1479 | 125 } |
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126 |
| 1479 | 127 /** |
| 128 * Read characters into a portion of an array, reading from the underlying | |
| 129 * stream at most once if necessary. | |
| 130 */ | |
| 1480 | 131 public synchronized int read(byte[] b, int off, int len) throws IOException { |
| 132 checkClosed(); | |
| 1479 | 133 int avail = count - pos; |
| 134 if (avail <= 0) { | |
| 1480 | 135 /* If the requested length is at least as large as the buffer, do not bother to copy the |
| 1479 | 136 bytes into the local buffer. In this way buffered streams will |
| 137 cascade harmlessly. */ | |
| 1480 | 138 if (len >= buf.length) { |
| 139 return super.read(b, off, len); | |
| 1479 | 140 } |
| 141 fill(); | |
| 142 avail = count - pos; | |
| 143 if (avail <= 0) return -1; | |
| 144 } | |
| 145 int cnt = (avail < len) ? avail : len; | |
| 1480 | 146 System.arraycopy(buf, pos, b, off, cnt); |
| 1479 | 147 pos += cnt; |
| 148 return cnt; | |
| 149 } | |
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150 |
| 1479 | 151 /** |
| 152 * See the general contract of the <code>skip</code> | |
| 153 * method of <code>InputStream</code>. | |
| 154 * | |
| 155 * @exception IOException if the stream does not support seek, | |
| 156 * or if this input stream has been closed by | |
| 157 * invoking its {@link #close()} method, or an | |
| 158 * I/O error occurs. | |
| 159 */ | |
| 160 public synchronized long skip(long n) throws IOException { | |
| 1480 | 161 checkClosed(); |
| 1479 | 162 long avail = count - pos; |
| 163 if (avail <= 0) { | |
| 1480 | 164 return super.skip(n); |
| 1479 | 165 } |
| 166 long skipped = (avail < n) ? avail : n; | |
| 167 pos += skipped; | |
| 168 return skipped; | |
| 169 } | |
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170 |
| 1479 | 171 /** |
| 172 * Returns an estimate of the number of bytes that can be read (or | |
| 173 * skipped over) from this input stream without blocking by the next | |
| 174 * invocation of a method for this input stream. The next invocation might be | |
| 175 * the same thread or another thread. A single read or skip of this | |
| 176 * many bytes will not block, but may read or skip fewer bytes. | |
| 177 * <p> | |
| 178 * This method returns the sum of the number of bytes remaining to be read in | |
| 179 * the buffer (<code>count - pos</code>) and the result of calling the | |
| 180 * {@link java.io.FilterInputStream#in in}.available(). | |
| 181 * | |
| 182 * @return an estimate of the number of bytes that can be read (or skipped | |
| 183 * over) from this input stream without blocking. | |
| 184 * @exception IOException if this input stream has been closed by | |
| 185 * invoking its {@link #close()} method, | |
| 186 * or an I/O error occurs. | |
| 187 */ | |
| 188 public synchronized int available() throws IOException { | |
| 189 int n = count - pos; | |
| 1480 | 190 int avail = super.available(); |
| 1479 | 191 return n > (Integer.MAX_VALUE - avail) |
| 192 ? Integer.MAX_VALUE | |
| 193 : n + avail; | |
| 194 } | |
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195 |
| 1480 | 196 public void mark(int readlimit) {} |
| 197 | |
| 198 public void reset() throws IOException { | |
| 199 throw new IOException("mark/reset not supported"); | |
| 1479 | 200 } |
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201 |
| 1479 | 202 public boolean markSupported() { |
| 1480 | 203 return false; |
| 1479 | 204 } |
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205 |
| 1479 | 206 /** |
| 207 * Closes this input stream and releases any system resources | |
| 208 * associated with the stream. | |
| 209 * Once the stream has been closed, further read(), available(), reset(), | |
| 210 * or skip() invocations will throw an IOException. | |
| 211 * Closing a previously closed stream has no effect. | |
| 212 * | |
| 213 * @exception IOException if an I/O error occurs. | |
| 214 */ | |
| 1480 | 215 public synchronized void close() throws IOException { |
| 216 isClosed = true; | |
| 217 super.close(); | |
| 1479 | 218 } |
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219 } |