SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package net.multiphasicapps.io;

import java.io.Reader;

/**
 * This is a reader which can read from a string.
 *
 * This class is not thread safe.
 *
 * @since 2018/11/04
 */
public class StringReader
    extends Reader
{
    /** The string to read from. */
    protected final String string;
    
    /** The string length. */
    protected final int length;
    
    /** The current position. */
    private int _at;
    
    /**
     * Initializes the reader.
     *
     * @param __s The input string.
     * @throws NullPointerException On null arguments.
     * @since 2018/11/04
     */
    public StringReader(String __s)
        throws NullPointerException
    {
        if (__s == null)
            throw new NullPointerException("NARG");
        
        this.string = __s;
        this.length = __s.length();
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/11/04
     */
    @Override
    public void close()
    {
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/11/04
     */
    @Override
    public int read(char[] __c, int __o, int __l)
        throws IndexOutOfBoundsException, NullPointerException
    {
        if (__c == null)
            throw new NullPointerException("NARG");
        if (__o < 0 || __l < 0 || (__o + __l) < 0 || (__o + __l) > __c.length)
            throw new IndexOutOfBoundsException("IOOB");
        
        // Determine the current position and string length
        int at = this._at,
            length = this.length,
            left = length - at;
        
        // EOF?
        if (at >= length)
            return -1;
        
        // Can only read so many characters
        String string = this.string;
        int max = Math.min(__l, left),
            limit = at + max;
        for (int o = __o; at < limit; at++, o++)
            __c[o] = string.charAt(at);
        
        // Set position for next time
        this._at = at;
        
        return max;
    }
}