/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.common.io;
import java.io.IOException;
import java.io.Reader;
/**
* A character stream whose source is a string that is <b>not thread safe</b>
* <p>
* (shay.banon
* )
*/
public class FastStringReader extends Reader implements CharSequence {
private String str;
private int length;
private int next = 0;
private int mark = 0;
/**
* Creates a new string reader.
*
* @param s String providing the character stream.
*/
public FastStringReader(String s) {
this.str = s;
this.length = s.length();
}
/**
* Check to make sure that the stream has not been closed
*/
private void ensureOpen() throws IOException {
if (length == -1)
throw new IOException("Stream closed");
}
@Override
public int length() {
return length;
}
@Override
public char charAt(int index) {
return str.charAt(index);
}
@Override
public CharSequence subSequence(int start, int end) {
return str.subSequence(start, end);
}
/**
* Reads a single character.
*
* @return The character read, or -1 if the end of the stream has been
* reached
* @throws IOException If an I/O error occurs
*/
@Override
public int read() throws IOException {
ensureOpen();
if (next >= length)
return -1;
return str.charAt(next++);
}
/**
* 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
* @throws IOException If an I/O error occurs
*/
@Override
public int read(char cbuf[], int off, int len) throws IOException {
ensureOpen();
if (len == 0) {
return 0;
}
if (next >= length)
return -1;
int n = Math.min(length - next, len);
str.getChars(next, next + n, cbuf, off);
next += n;
return n;
}
/**
* Skips the specified number of characters in the stream. Returns
* the number of characters that were skipped.
* <p>
* The <code>ns</code> parameter may be negative, even though the
* <code>skip</code> method of the {@link Reader} superclass throws
* an exception in this case. Negative values of <code>ns</code> cause the
* stream to skip backwards. Negative return values indicate a skip
* backwards. It is not possible to skip backwards past the beginning of
* the string.
* <p>
* If the entire string has been read or skipped, then this method has
* no effect and always returns 0.
*
* @throws IOException If an I/O error occurs
*/
@Override
public long skip(long ns) throws IOException {
ensureOpen();
if (next >= length)
return 0;
// Bound skip by beginning and end of the source
long n = Math.min(length - next, ns);
n = Math.max(-next, n);
next += n;
return n;
}
/**
* Tells whether this stream is ready to be read.
*
* @return True if the next read() is guaranteed not to block for input
* @throws IOException If the stream is closed
*/
@Override
public boolean ready() throws IOException {
ensureOpen();
return true;
}
/**
* Tells whether this stream supports the mark() operation, which it does.
*/
@Override
public boolean markSupported() {
return true;
}
/**
* Marks the present position in the stream. Subsequent calls to reset()
* will reposition the stream to this point.
*
* @param readAheadLimit Limit on the number of characters that may be
* read while still preserving the mark. Because
* the stream's input comes from a string, there
* is no actual limit, so this argument must not
* be negative, but is otherwise ignored.
* @throws IllegalArgumentException If readAheadLimit is < 0
* @throws IOException If an I/O error occurs
*/
@Override
public void mark(int readAheadLimit) throws IOException {
if (readAheadLimit < 0) {
throw new IllegalArgumentException("Read-ahead limit < 0");
}
ensureOpen();
mark = next;
}
/**
* Resets the stream to the most recent mark, or to the beginning of the
* string if it has never been marked.
*
* @throws IOException If an I/O error occurs
*/
@Override
public void reset() throws IOException {
ensureOpen();
next = mark;
}
/**
* Closes the stream and releases any system resources associated with
* it. Once the stream has been closed, further read(),
* ready(), mark(), or reset() invocations will throw an IOException.
* Closing a previously closed stream has no effect.
*/
@Override
public void close() {
length = -1;
}
@Override
public String toString() {
return str;
}
}