| /* |
| * Copyright (c) 1996, 2020, 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.nio.CharBuffer; |
| import java.util.Objects; |
| |
| /** |
| * Abstract class for reading character streams. The only methods that a |
| * subclass must implement are read(char[], int, int) and close(). Most |
| * subclasses, however, will override some of the methods defined here in order |
| * to provide higher efficiency, additional functionality, or both. |
| * |
| * |
| * @see BufferedReader |
| * @see LineNumberReader |
| * @see CharArrayReader |
| * @see InputStreamReader |
| * @see FileReader |
| * @see FilterReader |
| * @see PushbackReader |
| * @see PipedReader |
| * @see StringReader |
| * @see Writer |
| * |
| * @author Mark Reinhold |
| * @since 1.1 |
| */ |
| |
| public abstract class Reader implements Readable, Closeable { |
| |
| private static final int TRANSFER_BUFFER_SIZE = 8192; |
| |
| /** |
| * Returns a new {@code Reader} that reads no characters. The returned |
| * stream is initially open. The stream is closed by calling the |
| * {@code close()} method. Subsequent calls to {@code close()} have no |
| * effect. |
| * |
| * <p> While the stream is open, the {@code read()}, {@code read(char[])}, |
| * {@code read(char[], int, int)}, {@code read(CharBuffer)}, {@code |
| * ready()}, {@code skip(long)}, and {@code transferTo()} methods all |
| * behave as if end of stream has been reached. After the stream has been |
| * closed, these methods all throw {@code IOException}. |
| * |
| * <p> The {@code markSupported()} method returns {@code false}. The |
| * {@code mark()} and {@code reset()} methods throw an {@code IOException}. |
| * |
| * <p> The {@link #lock object} used to synchronize operations on the |
| * returned {@code Reader} is not specified. |
| * |
| * @return a {@code Reader} which reads no characters |
| * |
| * @since 11 |
| */ |
| public static Reader nullReader() { |
| return new Reader() { |
| private volatile boolean closed; |
| |
| private void ensureOpen() throws IOException { |
| if (closed) { |
| throw new IOException("Stream closed"); |
| } |
| } |
| |
| @Override |
| public int read() throws IOException { |
| ensureOpen(); |
| return -1; |
| } |
| |
| @Override |
| public int read(char[] cbuf, int off, int len) throws IOException { |
| Objects.checkFromIndexSize(off, len, cbuf.length); |
| ensureOpen(); |
| if (len == 0) { |
| return 0; |
| } |
| return -1; |
| } |
| |
| @Override |
| public int read(CharBuffer target) throws IOException { |
| Objects.requireNonNull(target); |
| ensureOpen(); |
| if (target.hasRemaining()) { |
| return -1; |
| } |
| return 0; |
| } |
| |
| @Override |
| public boolean ready() throws IOException { |
| ensureOpen(); |
| return false; |
| } |
| |
| @Override |
| public long skip(long n) throws IOException { |
| ensureOpen(); |
| return 0L; |
| } |
| |
| @Override |
| public long transferTo(Writer out) throws IOException { |
| Objects.requireNonNull(out); |
| ensureOpen(); |
| return 0L; |
| } |
| |
| @Override |
| public void close() { |
| closed = true; |
| } |
| }; |
| } |
| |
| /** |
| * The object used to synchronize operations on this stream. For |
| * efficiency, a character-stream object may use an object other than |
| * itself to protect critical sections. A subclass should therefore use |
| * the object in this field rather than {@code this} or a synchronized |
| * method. |
| */ |
| protected Object lock; |
| |
| /** |
| * Creates a new character-stream reader whose critical sections will |
| * synchronize on the reader itself. |
| */ |
| protected Reader() { |
| this.lock = this; |
| } |
| |
| /** |
| * Creates a new character-stream reader whose critical sections will |
| * synchronize on the given object. |
| * |
| * @param lock The Object to synchronize on. |
| */ |
| protected Reader(Object lock) { |
| if (lock == null) { |
| throw new NullPointerException(); |
| } |
| this.lock = lock; |
| } |
| |
| /** |
| * Attempts to read characters into the specified character buffer. |
| * The buffer is used as a repository of characters as-is: the only |
| * changes made are the results of a put operation. No flipping or |
| * rewinding of the buffer is performed. |
| * |
| * @param target the buffer to read characters into |
| * @return The number of characters added to the buffer, or |
| * -1 if this source of characters is at its end |
| * @throws IOException if an I/O error occurs |
| * @throws NullPointerException if target is null |
| * @throws java.nio.ReadOnlyBufferException if target is a read only buffer |
| * @since 1.5 |
| */ |
| public int read(CharBuffer target) throws IOException { |
| int len = target.remaining(); |
| char[] cbuf = new char[len]; |
| int n = read(cbuf, 0, len); |
| if (n > 0) |
| target.put(cbuf, 0, n); |
| return n; |
| } |
| |
| /** |
| * Reads a single character. This method will block until a character is |
| * available, an I/O error occurs, or the end of the stream is reached. |
| * |
| * <p> Subclasses that intend to support efficient single-character input |
| * should override this method. |
| * |
| * @return The character read, as an integer in the range 0 to 65535 |
| * ({@code 0x00-0xffff}), or -1 if the end of the stream has |
| * been reached |
| * |
| * @throws IOException If an I/O error occurs |
| */ |
| public int read() throws IOException { |
| char cb[] = new char[1]; |
| if (read(cb, 0, 1) == -1) |
| return -1; |
| else |
| return cb[0]; |
| } |
| |
| /** |
| * Reads characters into an array. This method will block until some input |
| * is available, an I/O error occurs, or the end of the stream is reached. |
| * |
| * @param cbuf Destination buffer |
| * |
| * @return The number of characters read, or -1 |
| * if the end of the stream |
| * has been reached |
| * |
| * @throws IOException If an I/O error occurs |
| */ |
| public int read(char cbuf[]) throws IOException { |
| return read(cbuf, 0, cbuf.length); |
| } |
| |
| /** |
| * Reads characters into a portion of an array. This method will block |
| * until some input is available, an I/O error occurs, or the end of the |
| * stream is reached. |
| * |
| * @param cbuf Destination buffer |
| * @param off Offset at which to start storing characters |
| * @param len Maximum number of characters to read |
| * |
| * @return The number of characters read, or -1 if the end of the |
| * stream has been reached |
| * |
| * @throws IOException If an I/O error occurs |
| * @throws IndexOutOfBoundsException |
| * If {@code off} is negative, or {@code len} is negative, |
| * or {@code len} is greater than {@code cbuf.length - off} |
| */ |
| public abstract int read(char cbuf[], int off, int len) throws IOException; |
| |
| /** Maximum skip-buffer size */ |
| private static final int maxSkipBufferSize = 8192; |
| |
| /** Skip buffer, null until allocated */ |
| private char skipBuffer[] = null; |
| |
| /** |
| * Skips characters. This method will block until some characters are |
| * available, an I/O error occurs, or the end of the stream is reached. |
| * |
| * @param n The number of characters to skip |
| * |
| * @return The number of characters actually skipped |
| * |
| * @throws IllegalArgumentException If {@code n} is negative. |
| * @throws IOException If an I/O error occurs |
| */ |
| public long skip(long n) throws IOException { |
| if (n < 0L) |
| throw new IllegalArgumentException("skip value is negative"); |
| int nn = (int) Math.min(n, maxSkipBufferSize); |
| synchronized (lock) { |
| if ((skipBuffer == null) || (skipBuffer.length < nn)) |
| skipBuffer = new char[nn]; |
| long r = n; |
| while (r > 0) { |
| int nc = read(skipBuffer, 0, (int)Math.min(r, nn)); |
| if (nc == -1) |
| break; |
| r -= nc; |
| } |
| return n - r; |
| } |
| } |
| |
| /** |
| * Tells whether this stream is ready to be read. |
| * |
| * @return True if the next read() is guaranteed not to block for input, |
| * false otherwise. Note that returning false does not guarantee that the |
| * next read will block. |
| * |
| * @throws IOException If an I/O error occurs |
| */ |
| public boolean ready() throws IOException { |
| return false; |
| } |
| |
| /** |
| * Tells whether this stream supports the mark() operation. The default |
| * implementation always returns false. Subclasses should override this |
| * method. |
| * |
| * @return true if and only if this stream supports the mark operation. |
| */ |
| public boolean markSupported() { |
| return false; |
| } |
| |
| /** |
| * Marks the present position in the stream. Subsequent calls to reset() |
| * will attempt to reposition the stream to this point. Not all |
| * character-input streams support the mark() operation. |
| * |
| * @param readAheadLimit Limit on the number of characters that may be |
| * read while still preserving the mark. After |
| * reading this many characters, attempting to |
| * reset the stream may fail. |
| * |
| * @throws IOException If the stream does not support mark(), |
| * or if some other I/O error occurs |
| */ |
| public void mark(int readAheadLimit) throws IOException { |
| throw new IOException("mark() not supported"); |
| } |
| |
| /** |
| * Resets the stream. If the stream has been marked, then attempt to |
| * reposition it at the mark. If the stream has not been marked, then |
| * attempt to reset it in some way appropriate to the particular stream, |
| * for example by repositioning it to its starting point. Not all |
| * character-input streams support the reset() operation, and some support |
| * reset() without supporting mark(). |
| * |
| * @throws IOException If the stream has not been marked, |
| * or if the mark has been invalidated, |
| * or if the stream does not support reset(), |
| * or if some other I/O error occurs |
| */ |
| public void reset() throws IOException { |
| throw new IOException("reset() not supported"); |
| } |
| |
| /** |
| * Closes the stream and releases any system resources associated with |
| * it. Once the stream has been closed, further read(), ready(), |
| * mark(), reset(), or skip() invocations will throw an IOException. |
| * Closing a previously closed stream has no effect. |
| * |
| * @throws IOException If an I/O error occurs |
| */ |
| public abstract void close() throws IOException; |
| |
| /** |
| * Reads all characters from this reader and writes the characters to the |
| * given writer in the order that they are read. On return, this reader |
| * will be at end of the stream. This method does not close either reader |
| * or writer. |
| * <p> |
| * This method may block indefinitely reading from the reader, or |
| * writing to the writer. The behavior for the case where the reader |
| * and/or writer is <i>asynchronously closed</i>, or the thread |
| * interrupted during the transfer, is highly reader and writer |
| * specific, and therefore not specified. |
| * <p> |
| * If an I/O error occurs reading from the reader or writing to the |
| * writer, then it may do so after some characters have been read or |
| * written. Consequently the reader may not be at end of the stream and |
| * one, or both, streams may be in an inconsistent state. It is strongly |
| * recommended that both streams be promptly closed if an I/O error occurs. |
| * |
| * @param out the writer, non-null |
| * @return the number of characters transferred |
| * @throws IOException if an I/O error occurs when reading or writing |
| * @throws NullPointerException if {@code out} is {@code null} |
| * |
| * @since 10 |
| */ |
| public long transferTo(Writer out) throws IOException { |
| Objects.requireNonNull(out, "out"); |
| long transferred = 0; |
| char[] buffer = new char[TRANSFER_BUFFER_SIZE]; |
| int nRead; |
| while ((nRead = read(buffer, 0, TRANSFER_BUFFER_SIZE)) >= 0) { |
| out.write(buffer, 0, nRead); |
| transferred += nRead; |
| } |
| return transferred; |
| } |
| |
| } |
