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/*
* Javolution - Java(TM) Solution for Real-Time and Embedded Systems
* Copyright (C) 2014 - Javolution (http://javolution.org/)
* All rights reserved.
*
* Permission to use, copy, modify, and distribute this software is
* freely granted, provided that this notice is preserved.
*/
package javolution.text;
import java.io.IOException;
import java.io.Reader;
/**
* A character stream whose source is a Text.
* This class is similar to {@link java.io.StringReader} but
* operates on {@link Text} instances and is not synchronized.
*
* @author javalama
* @version 6.1, January 17, 2014
*/
public class TextReader extends Reader {
private Text text;
private int length;
private int next = 0;
private int mark = 0;
/**
* Creates a new reader.
*
* @param text Text providing the character stream
*/
public TextReader(Text text) {
this.text = text;
this.length = text.length();
}
/**
* 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 {
if (next >= length)
return -1;
return text.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 {
if ((off < 0) || (off > cbuf.length) || (len < 0)
|| ((off + len) > cbuf.length) || ((off + len) < 0))
throw new IndexOutOfBoundsException();
if (len == 0)
return 0;
if (next >= length)
return -1;
int n = Math.min(length - next, len);
text.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.
*
* 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 {
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 {
if(text==null)
throw new IOException("TextReader is Closed");
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");
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 {
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() {
text = null;
}
}