From: Jim Weirich <jim@...>
Date: 2006-06-29T05:25:55+09:00
Subject: Re: Unicode roadmap?

Austin Ziegler wrote:
> Again, you are wrong. Horribly so. I *can* guarantee that sizeof(char)
> == sizeof(byte) if String#encoding is a single-byte encoding or is "raw"
> (or "binary", whichever Matz uses).

I think his point is that for any arbitrary string you cannot guarantee 
that it is a single byte encoding and that your code should be written:

  raise "Not PNG." unless (SINGLE_BYTE_ENCODINGS.include?(@top.encoding) 
&& @top[0, 8] == "\x89PNG\x0d\x0a\x1a\x0a")

Of course, if you can guarantee that @top is indeed a single byte 
encoded BEFORE hitting this line, then the encoding test is not needed 
(and I think you assume that).

But in the general case, it just seems easier to write:

  raise "Not PNG." unless @top.byte(0, 8) == "\x89PNG\x0d\x0a\x1a\x0a"

which will work in all cases, without any effort to ensure the 
precondition that the encoding is a single byte encoding.

-- Jim Weirich


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