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 cc.squirreljme.runtime.cldc.io;

/**
 * This encoder encodes input characters to standard UTF-8 sequences.
 *
 * Surrogate pairs will be encoded as 6 bytes.
 *
 * @since 2018/09/19
 */
public final class UTF8Encoder
    implements Encoder
{
    /**
     * {@inheritDoc}
     * @since 2018/11/06
     */
    @Override
    public final double averageSequenceLength()
    {
        return 1.3333;
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/09/21
     */
    @Override
    public int encode(char __c, byte[] __b, int __o, int __l)
        throws IndexOutOfBoundsException, NullPointerException
    {
        if (__b == null)
            throw new NullPointerException("NARG");
        if (__o < 0 || __l < 0 || (__o + __l) < 0 || (__o + __l) > __b.length)
            throw new IndexOutOfBoundsException("IOOB");
        
        // One byte
        if (__c >= 0x0000 && __c <= 0x007F)
        {
            if (__l < 1)
                return -1;
            
            __b[__o] = (byte)__c;
            
            return 1;
        }
        
        // Two Byte
        else if (__c >= 0x0080 && __c <= 0x07FF)
        {
            if (__l < 2)
                return -2;
            
            __b[__o + 0] = (byte)(((__c >>> 6) & 0b11111) | 0b110_00000); 
            __b[__o + 1] = (byte)((__c & 0b111111) | 0b10_000000);
            
            return 2;
        }
        
        // Three byte (__c >= 0x0800 && __c <= 0xFFFF)
        else
        {
            if (__l < 3)
                return -3;
                
            __b[__o + 0] = (byte)(((__c >>> 12) & 0b1111) | 0b1110_0000); 
            __b[__o + 1] = (byte)(((__c >>> 6) & 0b111111) | 0b10_000000);
            __b[__o + 2] = (byte)((__c & 0b111111) | 0b10_000000);
            
            return 3;
        }
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/10/13
     */
    @Override
    public final String encodingName()
    {
        return "utf-8";
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/12/08
     */
    @Override
    public final int maximumSequenceLength()
    {
        return 4;
    }
}