[JOS-Kernel] [TCP/IP Stack] HWAddr suggestions

[Gilbert Carl Herschberger II]

Here are my first suggestion for HWAddr.

class HWAddr
{
  static final int SIZE = 6;

  byte[] addr = new byte[ SIZE ];

  HWAddr( byte[] raw, int offset )
  {
    System.arraycopy( raw, offset, addr, 0, SIZE );
  }
};

Pass the entire raw array to HWAddr constructor. In C, it is just like

    char *raw = "a-very-long-string";
    puts( raw );

Inside EtherPacket.java,

    dest = new HWAddr(raw[0],raw[1],raw[2],raw[3],raw[4],raw[5]);

becomes

    dest = new HWAddr( raw, 0 );

and

    src = new HWAddr(raw[6],raw[7],raw[8],raw[9],raw[10],raw[11]);

becomes

    src = new HWAddr( raw, 6 );

-----

Going to the next level...

In the interest of high performance, bytes from an ethernet packet do not
have to be duplicated in HWAddr. The HWAddr object is immutable. It points
to the MAC Address. It might be written something like this:

class HWAddr
{
  byte[] raw;
  int offset;

  HWAddr( byte[] r, int o )
  {
    raw = r;
    offset = o;
  }
};

-----

Going to the next level: If you wanted to split HWAddr into SourceAddr and
TargetAddress, you'd have this:

    dest = new HWAddr( raw, 0 );

becomes

    dest = new SourceAddr( raw );

and

    src = new HWAddr( raw, 6 );

becomes

    src = new TargetAddr( raw );

SourceAddr and TargetAddr share all of the same behavior, except for offset
and class name.

class SourceAddr
{
  static final int OFFSET = 0;

  byte[] raw;

  SourceAddr( byte[] r )
  {
    raw = r
  }
};

and

class TargetAddr
{
  static final int OFFSET = 6;

  byte[] raw;

  TargetAddr( byte[] r )
  {
    raw = r;
  }
};


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