286 lines
9.5 KiB
Java
286 lines
9.5 KiB
Java
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/*
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* Copyright (c) 1996, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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/**
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* A character-stream reader that allows characters to be pushed back into the
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* stream.
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*
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* @author Mark Reinhold
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* @since 1.1
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*/
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public class PushbackReader extends FilterReader {
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/** Pushback buffer */
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private char[] buf;
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/** Current position in buffer */
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private int pos;
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/**
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* Creates a new pushback reader with a pushback buffer of the given size.
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*
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* @param in The reader from which characters will be read
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* @param size The size of the pushback buffer
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* @exception IllegalArgumentException if {@code size <= 0}
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*/
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public PushbackReader(Reader in, int size) {
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super(in);
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if (size <= 0) {
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throw new IllegalArgumentException("size <= 0");
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}
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this.buf = new char[size];
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this.pos = size;
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}
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/**
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* Creates a new pushback reader with a one-character pushback buffer.
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*
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* @param in The reader from which characters will be read
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*/
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public PushbackReader(Reader in) {
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this(in, 1);
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}
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/** Checks to make sure that the stream has not been closed. */
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private void ensureOpen() throws IOException {
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if (buf == null)
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throw new IOException("Stream closed");
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}
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/**
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* Reads a single character.
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*
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* @return The character read, or -1 if the end of the stream has been
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* reached
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*
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* @exception IOException If an I/O error occurs
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*/
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public int read() throws IOException {
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synchronized (lock) {
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ensureOpen();
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if (pos < buf.length)
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return buf[pos++];
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else
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return super.read();
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}
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}
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/**
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* Reads characters into a portion of an array.
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*
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* @param cbuf Destination buffer
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* @param off Offset at which to start writing characters
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* @param len Maximum number of characters to read
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*
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* @return The number of characters read, or -1 if the end of the
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* stream has been reached
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*
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* @exception IOException If an I/O error occurs
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* @exception IndexOutOfBoundsException {@inheritDoc}
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*/
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public int read(char cbuf[], int off, int len) throws IOException {
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synchronized (lock) {
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ensureOpen();
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try {
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if (len <= 0) {
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if (len < 0) {
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throw new IndexOutOfBoundsException();
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} else if ((off < 0) || (off > cbuf.length)) {
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throw new IndexOutOfBoundsException();
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}
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return 0;
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}
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int avail = buf.length - pos;
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if (avail > 0) {
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if (len < avail)
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avail = len;
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System.arraycopy(buf, pos, cbuf, off, avail);
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pos += avail;
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off += avail;
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len -= avail;
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}
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if (len > 0) {
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len = super.read(cbuf, off, len);
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if (len == -1) {
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return (avail == 0) ? -1 : avail;
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}
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return avail + len;
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}
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return avail;
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} catch (ArrayIndexOutOfBoundsException e) {
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throw new IndexOutOfBoundsException();
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}
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}
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}
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/**
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* Pushes back a single character by copying it to the front of the
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* pushback buffer. After this method returns, the next character to be read
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* will have the value <code>(char)c</code>.
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*
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* @param c The int value representing a character to be pushed back
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*
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* @exception IOException If the pushback buffer is full,
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* or if some other I/O error occurs
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*/
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public void unread(int c) throws IOException {
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synchronized (lock) {
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ensureOpen();
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if (pos == 0)
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throw new IOException("Pushback buffer overflow");
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buf[--pos] = (char) c;
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}
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}
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/**
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* Pushes back a portion of an array of characters by copying it to the
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* front of the pushback buffer. After this method returns, the next
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* character to be read will have the value <code>cbuf[off]</code>, the
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* character after that will have the value <code>cbuf[off+1]</code>, and
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* so forth.
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*
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* @param cbuf Character array
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* @param off Offset of first character to push back
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* @param len Number of characters to push back
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*
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* @exception IOException If there is insufficient room in the pushback
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* buffer, or if some other I/O error occurs
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*/
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public void unread(char cbuf[], int off, int len) throws IOException {
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synchronized (lock) {
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ensureOpen();
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if (len > pos)
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throw new IOException("Pushback buffer overflow");
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pos -= len;
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System.arraycopy(cbuf, off, buf, pos, len);
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}
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}
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/**
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* Pushes back an array of characters by copying it to the front of the
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* pushback buffer. After this method returns, the next character to be
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* read will have the value <code>cbuf[0]</code>, the character after that
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* will have the value <code>cbuf[1]</code>, and so forth.
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*
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* @param cbuf Character array to push back
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*
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* @exception IOException If there is insufficient room in the pushback
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* buffer, or if some other I/O error occurs
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*/
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public void unread(char cbuf[]) throws IOException {
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unread(cbuf, 0, cbuf.length);
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}
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/**
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* Tells whether this stream is ready to be read.
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*
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* @exception IOException If an I/O error occurs
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*/
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public boolean ready() throws IOException {
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synchronized (lock) {
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ensureOpen();
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return (pos < buf.length) || super.ready();
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}
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}
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/**
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* Marks the present position in the stream. The <code>mark</code>
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* for class <code>PushbackReader</code> always throws an exception.
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*
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* @exception IOException Always, since mark is not supported
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*/
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public void mark(int readAheadLimit) throws IOException {
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throw new IOException("mark/reset not supported");
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}
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/**
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* Resets the stream. The <code>reset</code> method of
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* <code>PushbackReader</code> always throws an exception.
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*
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* @exception IOException Always, since reset is not supported
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*/
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public void reset() throws IOException {
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throw new IOException("mark/reset not supported");
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}
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/**
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* Tells whether this stream supports the mark() operation, which it does
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* not.
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*/
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public boolean markSupported() {
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return false;
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}
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/**
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* Closes the stream and releases any system resources associated with
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* it. Once the stream has been closed, further read(),
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* unread(), ready(), or skip() invocations will throw an IOException.
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* Closing a previously closed stream has no effect. This method will block
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* while there is another thread blocking on the reader.
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*
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* @exception IOException If an I/O error occurs
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*/
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public void close() throws IOException {
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synchronized (lock) {
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super.close();
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buf = null;
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}
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}
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/**
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* Skips characters. This method will block until some characters are
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* available, an I/O error occurs, or the end of the stream is reached.
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*
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* @param n The number of characters to skip
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*
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* @return The number of characters actually skipped
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*
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* @exception IllegalArgumentException If <code>n</code> is negative.
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* @exception IOException If an I/O error occurs
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*/
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public long skip(long n) throws IOException {
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if (n < 0L)
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throw new IllegalArgumentException("skip value is negative");
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synchronized (lock) {
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ensureOpen();
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int avail = buf.length - pos;
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if (avail > 0) {
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if (n <= avail) {
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pos += n;
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return n;
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} else {
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pos = buf.length;
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n -= avail;
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}
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}
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return avail + super.skip(n);
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}
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}
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}
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