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Re: Unibyte characters, strings, and buffers

From: Stephen J. Turnbull
Subject: Re: Unibyte characters, strings, and buffers
Date: Sun, 30 Mar 2014 01:11:08 +0900

Eli Zaretskii writes:

 > I think [unibyte] is (or at least was) also a speed optimization.

It is.  Random access to position N multibyte buffer is average O(N),
and O(log N) with a position cache as used in XEmacs and I believe in
GNU Emacs too (haven't looked at GNU Emacs's implementation of buffer
movement since about v22, though).  This slows down mbox-based MUAs
like VM and RMail quite a bit if people use 8-bit or binary
content-transfer-encodings in their messages.

 > Reading or writing a huge buffer full of eight-bit characters might
 > be significantly slower if they are in their multibyte
 > representation.  Perhaps we should measure that.

This isn't true (Ben did measurements, as have the Python folks).
Coding systems are way faster than I/O.

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