public FieldIterator() 
{

}

 public String calcSize(int fieldNumber,
    String fieldName,
    String size,
    String type) 
{
        String result = " + ";
        if (type.startsWith("custom:"))
        {
            String javaFieldName = RecordUtil.getFieldName(fieldNumber, fieldName, 0);
            return result + javaFieldName + ".getSize()";
        }
        else if ("var".equals(size))
        {
            String javaFieldName = RecordUtil.getFieldName(fieldNumber,fieldName,0);
            return result + " ("+javaFieldName + ".length() *2)";
        }
        else if ("varword".equals(size))
        {
            String javaFieldName = RecordUtil.getFieldName(fieldNumber,fieldName,0);
            return result + javaFieldName + ".length * 2 + 2";
        } else
        {
            return result + size;
        }
}

 public String fillDecoder(String size,
    String type) 
{
        String javaType = RecordUtil.getType(size, type, 0);
        String result = "";
        if (javaType.equals("short"))
            result = "LittleEndian.getShort(data, pos + 0x" + Integer.toHexString(offset) + " + offset)";
        else if (javaType.equals("short[]"))
            result = "LittleEndian.getShortArray(data, pos + 0x" + Integer.toHexString(offset) + " + offset)";
        else if (javaType.equals("int"))
            result = "LittleEndian.getInt(data, pos + 0x" + Integer.toHexString(offset) + " + offset)";
        else if (javaType.equals("byte"))
            result = "data[ pos + 0x" + Integer.toHexString(offset) + " + offset ]";
        else if (javaType.equals("double"))
            result = "LittleEndian.getDouble(data, pos + 0x" + Integer.toHexString(offset) + " + offset)";
        else if (javaType.equals("String") && !type.equals("hbstring"))
            result = "StringUtil.getFromUnicode(data, pos + 0x" + Integer.toHexString(offset) + " + offset,("+ size + "-1)/2)";
        else if (javaType.equals("String") && type.equals("hbstring"))
            result = "StringUtil.getFromUnicodeHigh(data, pos + 0x" + Integer.toHexString(offset) + " + offset, ("+ size+"/2))";
        try
        {
            offset += Integer.parseInt(size);
        }
        catch (NumberFormatException ignore)
        {
        }
        return result;
}

This utility function returns a fill method entry for a given field

 public String fillDecoder2(int position,
    String name,
    String size,
    String type) 
{
        if (type.startsWith("custom:"))
        {
            StringBuffer result = new StringBuffer();
            result.append( RecordUtil.getFieldName( position, name, 0 ) );
            result.append( " = new " );
            String javaType = type.substring( 7 );
            result.append(javaType);
            result.append( "();\n");
            result.append( "        pos += " );
            result.append(RecordUtil.getFieldName(position, name, 0))
                    .append(".fillField(data,size,pos + offset + ")
                    .append(offset)
                    .append(")");
            return result.toString();
        }
        else
        {
            return RecordUtil.getFieldName(position, name, 30) +
                    " = " + fillDecoder(size, type);
        }
}

 public String serialiseEncoder(int fieldNumber,
    String fieldName,
    String size,
    String type) 
{
        String javaType = RecordUtil.getType(size, type, 0);
        String javaFieldName = RecordUtil.getFieldName(fieldNumber,fieldName,0);
        String result = "";
        if (type.startsWith("custom:"))
            result = "pos += " + javaFieldName + ".serializeField( pos + " + (offset+4) + " + offset, data );";
        else if (javaType.equals("short"))
            result = "LittleEndian.putShort(data, " + (offset+4) + " + offset + pos, " + javaFieldName + ");";
        else if (javaType.equals("short[]"))
            result = "LittleEndian.putShortArray(data, " + (offset+4) + " + offset + pos, " + javaFieldName + ");";
        else if (javaType.equals("int"))
            result = "LittleEndian.putInt(data, " + (offset+4) + " + offset + pos, " + javaFieldName + ");";
        else if (javaType.equals("byte"))
            result = "data[ " + (offset+4) + " + offset + pos ] = " + javaFieldName + ";";
        else if (javaType.equals("double"))
            result = "LittleEndian.putDouble(data, " + (offset+4) + " + offset + pos, " + javaFieldName + ");";
        else if (javaType.equals("String") && !type.equals("hbstring"))
            result = "StringUtil.putUncompressedUnicode("+ javaFieldName +", data, offset + pos + 4);";
        else if (javaType.equals("String") && type.equals("hbstring"))
            result = "StringUtil.putUncompressedUnicodeHigh("+ javaFieldName +", data, "+(offset+4)+" + offset + pos);";
        try
        {
            offset += Integer.parseInt(size);
        }
        catch (NumberFormatException ignore)
        {
        }
        return result;
}