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Panda Core is the core module of Panda Framework, it contains commonly used utility classes similar to apache-commons.
There is a newer version: 1.8.0
package panda.io.stream;

import java.io.Reader;
import java.io.Serializable;

import panda.io.Streams;

/**
 * {@link Reader} implementation that can read from String, StringBuffer, StringBuilder or
 * CharBuffer.
 * 
 * Note: Supports {@link #mark(int)} and {@link #reset()}.
 */
public class CharSequenceReader extends Reader implements Serializable {

	private static final long serialVersionUID = 1L;

	private final CharSequence charSequence;
	private int idx;
	private int mark;

	/**
	 * Construct a new instance with the specified character sequence.
	 * 
	 * @param charSequence The character sequence, may be {@code null}
	 */
	public CharSequenceReader(final CharSequence charSequence) {
		this.charSequence = charSequence != null ? charSequence : "";
	}

	/**
	 * Close resets the file back to the start and removes any marked position.
	 */
	@Override
	public void close() {
		idx = 0;
		mark = 0;
	}

	/**
	 * Mark the current position.
	 * 
	 * @param readAheadLimit ignored
	 */
	@Override
	public void mark(final int readAheadLimit) {
		mark = idx;
	}

	/**
	 * Mark is supported (returns true).
	 * 
	 * @return {@code true}
	 */
	@Override
	public boolean markSupported() {
		return true;
	}

	/**
	 * Read a single character.
	 * 
	 * @return the next character from the character sequence or -1 if the end has been reached.
	 */
	@Override
	public int read() {
		if (idx >= charSequence.length()) {
			return Streams.EOF;
		}
		else {
			return charSequence.charAt(idx++);
		}
	}

	/**
	 * Read the sepcified number of characters into the array.
	 * 
	 * @param array The array to store the characters in
	 * @param offset The starting position in the array to store
	 * @param length The maximum number of characters to read
	 * @return The number of characters read or -1 if there are no more
	 */
	@Override
	public int read(final char[] array, final int offset, final int length) {
		if (idx >= charSequence.length()) {
			return Streams.EOF;
		}
		if (array == null) {
			throw new NullPointerException("Character array is missing");
		}
		if (length < 0 || offset < 0 || offset + length > array.length) {
			throw new IndexOutOfBoundsException("Array Size=" + array.length + ", offset=" + offset + ", length="
					+ length);
		}
		int count = 0;
		for (int i = 0; i < length; i++) {
			final int c = read();
			if (c == Streams.EOF) {
				return count;
			}
			array[offset + i] = (char)c;
			count++;
		}
		return count;
	}

	/**
	 * Reset the reader to the last marked position (or the beginning if mark has not been called).
	 */
	@Override
	public void reset() {
		idx = mark;
	}

	/**
	 * Skip the specified number of characters.
	 * 
	 * @param n The number of characters to skip
	 * @return The actual number of characters skipped
	 */
	@Override
	public long skip(final long n) {
		if (n < 0) {
			throw new IllegalArgumentException("Number of characters to skip is less than zero: " + n);
		}
		if (idx >= charSequence.length()) {
			return Streams.EOF;
		}
		final int dest = (int)Math.min(charSequence.length(), idx + n);
		final int count = dest - idx;
		idx = dest;
		return count;
	}

	/**
	 * Return a String representation of the underlying character sequence.
	 * 
	 * @return The contents of the character sequence
	 */
	@Override
	public String toString() {
		return charSequence.toString();
	}
}