| /* |
| * Copyright (c) 1996, 2015, 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; |
| |
| |
| /** |
| * A character-stream reader that allows characters to be pushed back into the |
| * stream. |
| * |
| * @author Mark Reinhold |
| * @since 1.1 |
| */ |
| |
| public class PushbackReader extends FilterReader { |
| |
| /** Pushback buffer */ |
| private char[] buf; |
| |
| /** Current position in buffer */ |
| private int pos; |
| |
| /** |
| * Creates a new pushback reader with a pushback buffer of the given size. |
| * |
| * @param in The reader from which characters will be read |
| * @param size The size of the pushback buffer |
| * @exception IllegalArgumentException if {@code size <= 0} |
| */ |
| public PushbackReader(Reader in, int size) { |
| super(in); |
| if (size <= 0) { |
| throw new IllegalArgumentException("size <= 0"); |
| } |
| this.buf = new char[size]; |
| this.pos = size; |
| } |
| |
| /** |
| * Creates a new pushback reader with a one-character pushback buffer. |
| * |
| * @param in The reader from which characters will be read |
| */ |
| public PushbackReader(Reader in) { |
| this(in, 1); |
| } |
| |
| /** Checks to make sure that the stream has not been closed. */ |
| private void ensureOpen() throws IOException { |
| if (buf == null) |
| throw new IOException("Stream closed"); |
| } |
| |
| /** |
| * Reads a single character. |
| * |
| * @return The character read, or -1 if the end of the stream has been |
| * reached |
| * |
| * @exception IOException If an I/O error occurs |
| */ |
| public int read() throws IOException { |
| synchronized (lock) { |
| ensureOpen(); |
| if (pos < buf.length) |
| return buf[pos++]; |
| else |
| return super.read(); |
| } |
| } |
| |
| /** |
| * Reads characters into a portion of an array. |
| * |
| * @param cbuf Destination buffer |
| * @param off Offset at which to start writing 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 |
| * |
| * @exception IOException If an I/O error occurs |
| * @exception IndexOutOfBoundsException {@inheritDoc} |
| */ |
| public int read(char cbuf[], int off, int len) throws IOException { |
| synchronized (lock) { |
| ensureOpen(); |
| try { |
| if (len <= 0) { |
| if (len < 0) { |
| throw new IndexOutOfBoundsException(); |
| } else if ((off < 0) || (off > cbuf.length)) { |
| throw new IndexOutOfBoundsException(); |
| } |
| return 0; |
| } |
| int avail = buf.length - pos; |
| if (avail > 0) { |
| if (len < avail) |
| avail = len; |
| System.arraycopy(buf, pos, cbuf, off, avail); |
| pos += avail; |
| off += avail; |
| len -= avail; |
| } |
| if (len > 0) { |
| len = super.read(cbuf, off, len); |
| if (len == -1) { |
| return (avail == 0) ? -1 : avail; |
| } |
| return avail + len; |
| } |
| return avail; |
| } catch (ArrayIndexOutOfBoundsException e) { |
| throw new IndexOutOfBoundsException(); |
| } |
| } |
| } |
| |
| /** |
| * Pushes back a single character by copying it to the front of the |
| * pushback buffer. After this method returns, the next character to be read |
| * will have the value <code>(char)c</code>. |
| * |
| * @param c The int value representing a character to be pushed back |
| * |
| * @exception IOException If the pushback buffer is full, |
| * or if some other I/O error occurs |
| */ |
| public void unread(int c) throws IOException { |
| synchronized (lock) { |
| ensureOpen(); |
| if (pos == 0) |
| throw new IOException("Pushback buffer overflow"); |
| buf[--pos] = (char) c; |
| } |
| } |
| |
| /** |
| * Pushes back a portion of an array of characters by copying it to the |
| * front of the pushback buffer. After this method returns, the next |
| * character to be read will have the value <code>cbuf[off]</code>, the |
| * character after that will have the value <code>cbuf[off+1]</code>, and |
| * so forth. |
| * |
| * @param cbuf Character array |
| * @param off Offset of first character to push back |
| * @param len Number of characters to push back |
| * |
| * @exception IOException If there is insufficient room in the pushback |
| * buffer, or if some other I/O error occurs |
| */ |
| public void unread(char cbuf[], int off, int len) throws IOException { |
| synchronized (lock) { |
| ensureOpen(); |
| if (len > pos) |
| throw new IOException("Pushback buffer overflow"); |
| pos -= len; |
| System.arraycopy(cbuf, off, buf, pos, len); |
| } |
| } |
| |
| /** |
| * Pushes back an array of characters by copying it to the front of the |
| * pushback buffer. After this method returns, the next character to be |
| * read will have the value <code>cbuf[0]</code>, the character after that |
| * will have the value <code>cbuf[1]</code>, and so forth. |
| * |
| * @param cbuf Character array to push back |
| * |
| * @exception IOException If there is insufficient room in the pushback |
| * buffer, or if some other I/O error occurs |
| */ |
| public void unread(char cbuf[]) throws IOException { |
| unread(cbuf, 0, cbuf.length); |
| } |
| |
| /** |
| * Tells whether this stream is ready to be read. |
| * |
| * @exception IOException If an I/O error occurs |
| */ |
| public boolean ready() throws IOException { |
| synchronized (lock) { |
| ensureOpen(); |
| return (pos < buf.length) || super.ready(); |
| } |
| } |
| |
| /** |
| * Marks the present position in the stream. The <code>mark</code> |
| * for class <code>PushbackReader</code> always throws an exception. |
| * |
| * @exception IOException Always, since mark is not supported |
| */ |
| public void mark(int readAheadLimit) throws IOException { |
| throw new IOException("mark/reset not supported"); |
| } |
| |
| /** |
| * Resets the stream. The <code>reset</code> method of |
| * <code>PushbackReader</code> always throws an exception. |
| * |
| * @exception IOException Always, since reset is not supported |
| */ |
| public void reset() throws IOException { |
| throw new IOException("mark/reset not supported"); |
| } |
| |
| /** |
| * Tells whether this stream supports the mark() operation, which it does |
| * not. |
| */ |
| public boolean markSupported() { |
| return false; |
| } |
| |
| /** |
| * Closes the stream and releases any system resources associated with |
| * it. Once the stream has been closed, further read(), |
| * unread(), ready(), or skip() invocations will throw an IOException. |
| * Closing a previously closed stream has no effect. This method will block |
| * while there is another thread blocking on the reader. |
| * |
| * @exception IOException If an I/O error occurs |
| */ |
| public void close() throws IOException { |
| synchronized (lock) { |
| super.close(); |
| buf = 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 |
| * |
| * @exception IllegalArgumentException If <code>n</code> is negative. |
| * @exception IOException If an I/O error occurs |
| */ |
| public long skip(long n) throws IOException { |
| if (n < 0L) |
| throw new IllegalArgumentException("skip value is negative"); |
| synchronized (lock) { |
| ensureOpen(); |
| int avail = buf.length - pos; |
| if (avail > 0) { |
| if (n <= avail) { |
| pos += n; |
| return n; |
| } else { |
| pos = buf.length; |
| n -= avail; |
| } |
| } |
| return avail + super.skip(n); |
| } |
| } |
| } |