A few questiosn about encoding

[Zero Piraeus]

:

On 14 June 2013 01:34, Nick the Gr33k <support at superhost.gr> wrote:
> Why doesn't it work like this?
>
> leading 0 = 1 byte flag
> leading 1 = 2 bytes flag
> leading 00 = 3 bytes flag
> leading 01 = 4 bytes flag
> leading 10 = 5 bytes flag
> leading 11 = 6 bytes flag
>
> Wouldn't it be more logical?

Think about it. Let's say that, as per your scheme, a leading 0
indicates "1 byte" (as is indeed the case in UTF8). What things could
follow that leading 0? How does that impact your choice of a leading
00 or 01 for other numbers of bytes?

... okay, you're obviously going to need to be spoon-fed a little more
than that. Here's a byte:

  01010101

Is that a single byte representing a code point in the 0-127 range, or
the first of 4 bytes representing something else, in your proposed
scheme? How can you tell?

Now look at the way UTF8 does it:
<http://en.wikipedia.org/wiki/Utf-8#Description>

Really, follow the link and study the table carefully. Don't continue
reading this until you believe you understand the choices that the
designers of UTF8 made, and why they made them.

Pay particular attention to the possible values for byte 1. Do you
notice the difference between that scheme, and yours:

  0xxxxxxx
  1xxxxxxx
  00xxxxxx
  01xxxxxx
  10xxxxxx
  11xxxxxx

If you don't see it, keep looking until you do ... this email gives
you more than enough hints to work it out. Don't ask someone here to
explain it to you. If you want to become competent, you must use your
brain.

 -[]z.