1 /* 2 * Copyright (c) 1994, 2018, 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.util.Arrays; 29 import java.util.Objects; 30 31 /** 32 * A {@code ByteArrayInputStream} contains 33 * an internal buffer that contains bytes that 34 * may be read from the stream. An internal 35 * counter keeps track of the next byte to 36 * be supplied by the {@code read} method. 37 * <p> 38 * Closing a {@code ByteArrayInputStream} has no effect. The methods in 39 * this class can be called after the stream has been closed without 40 * generating an {@code IOException}. 41 * 42 * @author Arthur van Hoff 43 * @see java.io.StringBufferInputStream 44 * @since 1.0 45 */ 46 public class ByteArrayInputStream extends InputStream { 47 48 /** 49 * An array of bytes that was provided 50 * by the creator of the stream. Elements {@code buf[0]} 51 * through {@code buf[count-1]} are the 52 * only bytes that can ever be read from the 53 * stream; element {@code buf[pos]} is 54 * the next byte to be read. 55 */ 56 protected byte buf[]; 57 58 /** 59 * The index of the next character to read from the input stream buffer. 60 * This value should always be nonnegative 61 * and not larger than the value of {@code count}. 62 * The next byte to be read from the input stream buffer 63 * will be {@code buf[pos]}. 64 */ 65 protected int pos; 66 67 /** 68 * The currently marked position in the stream. 69 * ByteArrayInputStream objects are marked at position zero by 70 * default when constructed. They may be marked at another 71 * position within the buffer by the {@code mark()} method. 72 * The current buffer position is set to this point by the 73 * {@code reset()} method. 74 * <p> 75 * If no mark has been set, then the value of mark is the offset 76 * passed to the constructor (or 0 if the offset was not supplied). 77 * 78 * @since 1.1 79 */ 80 protected int mark = 0; 81 82 /** 83 * The index one greater than the last valid character in the input 84 * stream buffer. 85 * This value should always be nonnegative 86 * and not larger than the length of {@code buf}. 87 * It is one greater than the position of 88 * the last byte within {@code buf} that 89 * can ever be read from the input stream buffer. 90 */ 91 protected int count; 92 93 /** 94 * Creates a {@code ByteArrayInputStream} 95 * so that it uses {@code buf} as its 96 * buffer array. 97 * The buffer array is not copied. 98 * The initial value of {@code pos} 99 * is {@code 0} and the initial value 100 * of {@code count} is the length of 101 * {@code buf}. 102 * 103 * @param buf the input buffer. 104 */ ByteArrayInputStream(byte buf[])105 public ByteArrayInputStream(byte buf[]) { 106 this.buf = buf; 107 this.pos = 0; 108 this.count = buf.length; 109 } 110 111 /** 112 * Creates {@code ByteArrayInputStream} 113 * that uses {@code buf} as its 114 * buffer array. The initial value of {@code pos} 115 * is {@code offset} and the initial value 116 * of {@code count} is the minimum of {@code offset+length} 117 * and {@code buf.length}. 118 * The buffer array is not copied. The buffer's mark is 119 * set to the specified offset. 120 * 121 * @param buf the input buffer. 122 * @param offset the offset in the buffer of the first byte to read. 123 * @param length the maximum number of bytes to read from the buffer. 124 */ ByteArrayInputStream(byte buf[], int offset, int length)125 public ByteArrayInputStream(byte buf[], int offset, int length) { 126 this.buf = buf; 127 this.pos = offset; 128 this.count = Math.min(offset + length, buf.length); 129 this.mark = offset; 130 } 131 132 /** 133 * Reads the next byte of data from this input stream. The value 134 * byte is returned as an {@code int} in the range 135 * {@code 0} to {@code 255}. If no byte is available 136 * because the end of the stream has been reached, the value 137 * {@code -1} is returned. 138 * <p> 139 * This {@code read} method 140 * cannot block. 141 * 142 * @return the next byte of data, or {@code -1} if the end of the 143 * stream has been reached. 144 */ read()145 public synchronized int read() { 146 return (pos < count) ? (buf[pos++] & 0xff) : -1; 147 } 148 149 /** 150 * Reads up to {@code len} bytes of data into an array of bytes from this 151 * input stream. If {@code pos} equals {@code count}, then {@code -1} is 152 * returned to indicate end of file. Otherwise, the number {@code k} of 153 * bytes read is equal to the smaller of {@code len} and {@code count-pos}. 154 * If {@code k} is positive, then bytes {@code buf[pos]} through 155 * {@code buf[pos+k-1]} are copied into {@code b[off]} through 156 * {@code b[off+k-1]} in the manner performed by {@code System.arraycopy}. 157 * The value {@code k} is added into {@code pos} and {@code k} is returned. 158 * <p> 159 * This {@code read} method cannot block. 160 * 161 * @param b the buffer into which the data is read. 162 * @param off the start offset in the destination array {@code b} 163 * @param len the maximum number of bytes read. 164 * @return the total number of bytes read into the buffer, or 165 * {@code -1} if there is no more data because the end of 166 * the stream has been reached. 167 * @throws NullPointerException If {@code b} is {@code null}. 168 * @throws IndexOutOfBoundsException If {@code off} is negative, 169 * {@code len} is negative, or {@code len} is greater than 170 * {@code b.length - off} 171 */ read(byte b[], int off, int len)172 public synchronized int read(byte b[], int off, int len) { 173 Objects.checkFromIndexSize(off, len, b.length); 174 175 if (pos >= count) { 176 return -1; 177 } 178 179 int avail = count - pos; 180 if (len > avail) { 181 len = avail; 182 } 183 if (len <= 0) { 184 return 0; 185 } 186 System.arraycopy(buf, pos, b, off, len); 187 pos += len; 188 return len; 189 } 190 readAllBytes()191 public synchronized byte[] readAllBytes() { 192 byte[] result = Arrays.copyOfRange(buf, pos, count); 193 pos = count; 194 return result; 195 } 196 readNBytes(byte[] b, int off, int len)197 public int readNBytes(byte[] b, int off, int len) { 198 int n = read(b, off, len); 199 return n == -1 ? 0 : n; 200 } 201 transferTo(OutputStream out)202 public synchronized long transferTo(OutputStream out) throws IOException { 203 int len = count - pos; 204 out.write(buf, pos, len); 205 pos = count; 206 return len; 207 } 208 209 /** 210 * Skips {@code n} bytes of input from this input stream. Fewer 211 * bytes might be skipped if the end of the input stream is reached. 212 * The actual number {@code k} 213 * of bytes to be skipped is equal to the smaller 214 * of {@code n} and {@code count-pos}. 215 * The value {@code k} is added into {@code pos} 216 * and {@code k} is returned. 217 * 218 * @param n the number of bytes to be skipped. 219 * @return the actual number of bytes skipped. 220 */ skip(long n)221 public synchronized long skip(long n) { 222 long k = count - pos; 223 if (n < k) { 224 k = n < 0 ? 0 : n; 225 } 226 227 pos += k; 228 return k; 229 } 230 231 /** 232 * Returns the number of remaining bytes that can be read (or skipped over) 233 * from this input stream. 234 * <p> 235 * The value returned is {@code count - pos}, 236 * which is the number of bytes remaining to be read from the input buffer. 237 * 238 * @return the number of remaining bytes that can be read (or skipped 239 * over) from this input stream without blocking. 240 */ 241 public synchronized int available() { 242 return count - pos; 243 } 244 245 /** 246 * Tests if this {@code InputStream} supports mark/reset. The 247 * {@code markSupported} method of {@code ByteArrayInputStream} 248 * always returns {@code true}. 249 * 250 * @since 1.1 251 */ 252 public boolean markSupported() { 253 return true; 254 } 255 256 /** 257 * Set the current marked position in the stream. 258 * ByteArrayInputStream objects are marked at position zero by 259 * default when constructed. They may be marked at another 260 * position within the buffer by this method. 261 * <p> 262 * If no mark has been set, then the value of the mark is the 263 * offset passed to the constructor (or 0 if the offset was not 264 * supplied). 265 * 266 * <p> Note: The {@code readAheadLimit} for this class 267 * has no meaning. 268 * 269 * @since 1.1 270 */ 271 public void mark(int readAheadLimit) { 272 mark = pos; 273 } 274 275 /** 276 * Resets the buffer to the marked position. The marked position 277 * is 0 unless another position was marked or an offset was specified 278 * in the constructor. 279 */ 280 public synchronized void reset() { 281 pos = mark; 282 } 283 284 /** 285 * Closing a {@code ByteArrayInputStream} has no effect. The methods in 286 * this class can be called after the stream has been closed without 287 * generating an {@code IOException}. 288 */ 289 public void close() throws IOException { 290 } 291 292 } 293