[Python-Dev] Mailbox module - timings and functionality changes

[Guido van Rossum]

On Wed, Jun 30, 2010 at 9:42 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> On Tue, 29 Jun 2010 20:05:29 -0400
> "R. David Murray" <rdmurray at bitdance.com> wrote:
>>
>> I would imagine Guido is talking about an io.TextIOWrapper...in other
>> words, take the binary file you've just finished grabbing info
>> from, and reread it as a text file in order to grab the actual
>> message content.
>
> This sounds a bit suboptimal to me (and introduces race conditions if
> e.g. the file is replaced with another one before you reopen it). You
> could instead decode the binary data by yourself, especially if you
> have already stored that data somewhere.

That's why I proposed not reopening but wrapping.

Of course the contents of the file could still change, but that's a
limitation of how the mailbox module works -- it builds a TOC and
expects the file not to change.

> Also, please note that values used by seek() and tell() on
> text I/O are "opaque cookies". While they can happen to match the
> raw binary file position, it is a mere coincidence (or an
> implementation detail, at your will). Therefore, reusing tell() values
> of a binary file to seek() a TextIOWrapper accessing the same file
> is wrong.

Well, um, I actually designed it carefully so that bytes offsets
*would* work as text offsets in those cases where they make sense at
all.

-- 
--Guido van Rossum (python.org/~guido)