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annotate src/goodjava/io/BufferedInputStream.java @ 1487:044a360c2300
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| author | Franklin Schmidt <fschmidt@gmail.com> |
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| date | Fri, 01 May 2020 16:17:20 -0600 |
| parents | 97740900c820 |
| children | fe237d72b234 |
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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 { |
| 26 private final byte buf[]; | |
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27 |
| 1479 | 28 /** |
| 29 * The index one greater than the index of the last valid byte in | |
| 30 * the buffer. | |
| 31 * This value is always | |
| 32 * in the range <code>0</code> through <code>buf.length</code>; | |
| 33 * elements <code>buf[0]</code> through <code>buf[count-1] | |
| 34 * </code>contain buffered input data obtained | |
| 1480 | 35 * from the underlying input stream. |
| 1479 | 36 */ |
| 1480 | 37 private int count; |
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38 |
| 1479 | 39 /** |
| 40 * The current position in the buffer. This is the index of the next | |
| 41 * character to be read from the <code>buf</code> array. | |
| 42 * <p> | |
| 43 * This value is always in the range <code>0</code> | |
| 44 * through <code>count</code>. If it is less | |
| 45 * than <code>count</code>, then <code>buf[pos]</code> | |
| 46 * is the next byte to be supplied as input; | |
| 47 * if it is equal to <code>count</code>, then | |
| 48 * the next <code>read</code> or <code>skip</code> | |
| 49 * operation will require more bytes to be | |
| 50 * read from the contained input stream. | |
| 51 * | |
| 52 * @see java.io.BufferedInputStream#buf | |
| 53 */ | |
| 1480 | 54 private int pos; |
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55 |
| 1479 | 56 /** |
| 57 * Creates a <code>BufferedInputStream</code> | |
| 58 * and saves its argument, the input stream | |
| 59 * <code>in</code>, for later use. An internal | |
| 60 * buffer array is created and stored in <code>buf</code>. | |
| 61 * | |
| 62 * @param in the underlying input stream. | |
| 63 */ | |
| 64 public BufferedInputStream(InputStream in) { | |
| 1483 | 65 this(in, 8192); |
| 1479 | 66 } |
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67 |
| 1479 | 68 /** |
| 69 * Creates a <code>BufferedInputStream</code> | |
| 70 * with the specified buffer size, | |
| 71 * and saves its argument, the input stream | |
| 72 * <code>in</code>, for later use. An internal | |
| 73 * buffer array of length <code>size</code> | |
| 74 * is created and stored in <code>buf</code>. | |
| 75 * | |
| 76 * @param in the underlying input stream. | |
| 77 * @param size the buffer size. | |
| 78 */ | |
| 79 public BufferedInputStream(InputStream in, int size) { | |
| 80 super(in); | |
| 81 buf = new byte[size]; | |
| 82 } | |
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83 |
| 1479 | 84 /** |
| 1480 | 85 * Fills the buffer with more data. |
| 1479 | 86 * Assumes that it is being called by a synchronized method. |
| 87 * This method also assumes that all data has already been read in, | |
| 88 * hence pos > count. | |
| 89 */ | |
| 90 private void fill() throws IOException { | |
| 1480 | 91 pos = 0; |
| 92 count = 0; | |
| 93 int n = super.read(buf, 0, buf.length); | |
| 1479 | 94 if (n > 0) |
| 1480 | 95 count = n; |
| 1479 | 96 } |
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97 |
| 1479 | 98 /** |
| 99 * See | |
| 100 * the general contract of the <code>read</code> | |
| 101 * method of <code>InputStream</code>. | |
| 102 * | |
| 103 * @return the next byte of data, or <code>-1</code> if the end of the | |
| 104 * stream is reached. | |
| 105 * @exception IOException if this input stream has been closed by | |
| 106 * invoking its {@link #close()} method, | |
| 107 * or an I/O error occurs. | |
| 108 * @see java.io.FilterInputStream#in | |
| 109 */ | |
| 110 public synchronized int read() throws IOException { | |
| 111 if (pos >= count) { | |
| 112 fill(); | |
| 113 if (pos >= count) | |
| 114 return -1; | |
| 115 } | |
| 1480 | 116 return buf[pos++] & 0xff; |
| 1479 | 117 } |
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118 |
| 1479 | 119 /** |
| 120 * Read characters into a portion of an array, reading from the underlying | |
| 121 * stream at most once if necessary. | |
| 122 */ | |
| 1480 | 123 public synchronized int read(byte[] b, int off, int len) throws IOException { |
| 1479 | 124 int avail = count - pos; |
| 125 if (avail <= 0) { | |
| 1480 | 126 /* If the requested length is at least as large as the buffer, do not bother to copy the |
| 1479 | 127 bytes into the local buffer. In this way buffered streams will |
| 128 cascade harmlessly. */ | |
| 1480 | 129 if (len >= buf.length) { |
| 130 return super.read(b, off, len); | |
| 1479 | 131 } |
| 132 fill(); | |
| 133 avail = count - pos; | |
| 134 if (avail <= 0) return -1; | |
| 135 } | |
| 136 int cnt = (avail < len) ? avail : len; | |
| 1480 | 137 System.arraycopy(buf, pos, b, off, cnt); |
| 1479 | 138 pos += cnt; |
| 139 return cnt; | |
| 140 } | |
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141 |
| 1479 | 142 /** |
| 143 * See the general contract of the <code>skip</code> | |
| 144 * method of <code>InputStream</code>. | |
| 145 * | |
| 146 * @exception IOException if the stream does not support seek, | |
| 147 * or if this input stream has been closed by | |
| 148 * invoking its {@link #close()} method, or an | |
| 149 * I/O error occurs. | |
| 150 */ | |
| 151 public synchronized long skip(long n) throws IOException { | |
| 152 long avail = count - pos; | |
| 153 if (avail <= 0) { | |
| 1480 | 154 return super.skip(n); |
| 1479 | 155 } |
| 156 long skipped = (avail < n) ? avail : n; | |
| 157 pos += skipped; | |
| 158 return skipped; | |
| 159 } | |
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160 |
| 1479 | 161 /** |
| 162 * Returns an estimate of the number of bytes that can be read (or | |
| 163 * skipped over) from this input stream without blocking by the next | |
| 164 * invocation of a method for this input stream. The next invocation might be | |
| 165 * the same thread or another thread. A single read or skip of this | |
| 166 * many bytes will not block, but may read or skip fewer bytes. | |
| 167 * <p> | |
| 168 * This method returns the sum of the number of bytes remaining to be read in | |
| 169 * the buffer (<code>count - pos</code>) and the result of calling the | |
| 170 * {@link java.io.FilterInputStream#in in}.available(). | |
| 171 * | |
| 172 * @return an estimate of the number of bytes that can be read (or skipped | |
| 173 * over) from this input stream without blocking. | |
| 174 * @exception IOException if this input stream has been closed by | |
| 175 * invoking its {@link #close()} method, | |
| 176 * or an I/O error occurs. | |
| 177 */ | |
| 178 public synchronized int available() throws IOException { | |
| 179 int n = count - pos; | |
| 1480 | 180 int avail = super.available(); |
| 1479 | 181 return n > (Integer.MAX_VALUE - avail) |
| 182 ? Integer.MAX_VALUE | |
| 183 : n + avail; | |
| 184 } | |
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185 |
| 1480 | 186 public void mark(int readlimit) {} |
| 187 | |
| 188 public void reset() throws IOException { | |
| 189 throw new IOException("mark/reset not supported"); | |
| 1479 | 190 } |
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191 |
| 1479 | 192 public boolean markSupported() { |
| 1480 | 193 return false; |
| 1479 | 194 } |
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195 |
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196 } |