com.epam.deltix.util.io.CharSequenceReader Maven / Gradle / Ivy
/*
* Copyright 2021 EPAM Systems, Inc
*
* See the NOTICE file distributed with this work for additional information
* regarding copyright ownership. Licensed 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 com.epam.deltix.util.io;
import java.io.*;
/**
* A character stream whose source is a CharSequence.
* Patterned after StringReader.
*/
public class CharSequenceReader extends Reader {
private CharSequence 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 CharSequenceReader(CharSequence 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 (str == 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 (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
*
* @exception IOException If an I/O error occurs
*/
public int read(char cbuf[], int off, int len) throws IOException {
synchronized (lock) {
ensureOpen();
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
((off + len) > cbuf.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return 0;
}
if (next >= length)
return -1;
int n = 0;
while (next < length && n < len)
cbuf [off + n++] = str.charAt (next++);
return n;
}
}
/**
* Skips the specified number of characters in the stream. Returns
* the number of characters that were skipped.
*
* The ns parameter may be negative, even though the
* skip method of the {@link Reader} superclass throws
* an exception in this case. Negative values of ns 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.
*
* If the entire string has been read or skipped, then this method has
* no effect and always returns 0.
*
* @exception IOException If an I/O error occurs
*/
public long skip(long ns) throws IOException {
synchronized (lock) {
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
*
* @exception IOException If the stream is closed
*/
public boolean ready() throws IOException {
synchronized (lock) {
ensureOpen();
return true;
}
}
/**
* Tells whether this stream supports the mark() operation, which it does.
*/
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.
*
* @exception IllegalArgumentException If readAheadLimit is < 0
* @exception IOException If an I/O error occurs
*/
public void mark(int readAheadLimit) throws IOException {
if (readAheadLimit < 0){
throw new IllegalArgumentException("Read-ahead limit < 0");
}
synchronized (lock) {
ensureOpen();
mark = next;
}
}
/**
* Resets the stream to the most recent mark, or to the beginning of the
* string if it has never been marked.
*
* @exception IOException If an I/O error occurs
*/
public void reset() throws IOException {
synchronized (lock) {
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.
*/
public void close() {
str = null;
}
}