214 lines
6.8 KiB
Java
214 lines
6.8 KiB
Java
/*
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* Copyright (c) 1996, 2023, 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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import java.util.Objects;
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/**
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* A character stream whose source is a string.
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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 StringReader extends Reader {
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private final int length;
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private String str;
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private int next = 0;
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private int mark = 0;
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/**
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* Creates a new string reader.
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*
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* @param s String providing the character stream.
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*/
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public StringReader(String s) {
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this.length = s.length();
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this.str = s;
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}
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/** Check to make sure that the stream has not been closed */
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private void ensureOpen() throws IOException {
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if (str == 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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* @throws 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 (next >= length)
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return -1;
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return str.charAt(next++);
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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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* <p> If {@code len} is zero, then no characters are read and {@code 0} is
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* returned; otherwise, there is an attempt to read at least one character.
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* If no character is available because the stream is at its end, the value
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* {@code -1} is returned; otherwise, at least one character is read and
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* stored into {@code cbuf}.
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*
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* @param cbuf {@inheritDoc}
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* @param off {@inheritDoc}
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* @param len {@inheritDoc}
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*
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* @return {@inheritDoc}
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*
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* @throws IndexOutOfBoundsException {@inheritDoc}
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* @throws IOException {@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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Objects.checkFromIndexSize(off, len, cbuf.length);
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if (len == 0) {
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return 0;
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}
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if (next >= length)
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return -1;
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int n = Math.min(length - next, len);
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str.getChars(next, next + n, cbuf, off);
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next += n;
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return n;
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}
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}
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/**
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* Skips characters. If the stream is already at its end before this method
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* is invoked, then no characters are skipped and zero is returned.
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*
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* <p>The {@code n} parameter may be negative, even though the
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* {@code skip} method of the {@link Reader} superclass throws
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* an exception in this case. Negative values of {@code n} cause the
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* stream to skip backwards. Negative return values indicate a skip
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* backwards. It is not possible to skip backwards past the beginning of
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* the string.
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*
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* <p>If the entire string has been read or skipped, then this method has
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* no effect and always returns {@code 0}.
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*
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* @param n {@inheritDoc}
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*
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* @return {@inheritDoc}
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*
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* @throws IOException {@inheritDoc}
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*/
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public long skip(long n) throws IOException {
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synchronized (lock) {
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ensureOpen();
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if (next >= length)
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return 0;
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// Bound skip by beginning and end of the source
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long r = Math.min(length - next, n);
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r = Math.max(-next, r);
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next += (int)r;
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return r;
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}
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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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* @return True if the next read() is guaranteed not to block for input
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*
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* @throws IOException If the stream is closed
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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 true;
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}
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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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*/
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public boolean markSupported() {
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return true;
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}
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/**
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* Marks the present position in the stream. Subsequent calls to reset()
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* will reposition the stream to this point.
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*
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* @param readAheadLimit Limit on the number of characters that may be
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* read while still preserving the mark. Because
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* the stream's input comes from a string, there
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* is no actual limit, so this argument must not
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* be negative, but is otherwise ignored.
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*
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* @throws IllegalArgumentException If {@code readAheadLimit < 0}
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* @throws IOException If an I/O error occurs
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*/
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public void mark(int readAheadLimit) throws IOException {
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if (readAheadLimit < 0){
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throw new IllegalArgumentException("Read-ahead limit < 0");
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}
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synchronized (lock) {
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ensureOpen();
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mark = next;
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}
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}
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/**
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* Resets the stream to the most recent mark, or to the beginning of the
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* string if it has never been marked.
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*
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* @throws IOException If an I/O error occurs
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*/
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public void reset() throws IOException {
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synchronized (lock) {
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ensureOpen();
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next = mark;
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}
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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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* ready(), mark(), or reset() 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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public void close() {
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synchronized (lock) {
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str = null;
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}
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}
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}
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