From: Bruno Haible <bruno@clisp.org>
To: ag <aga.chatzimanikas@gmail.com>
Cc: "Tim Rühsen" <tim.ruehsen@gmx.de>, bug-gnulib@gnu.org
Subject: Re: string types
Date: Fri, 27 Dec 2019 11:51:18 +0100 [thread overview]
Message-ID: <2179574.G9OhZXe8sF@omega> (raw)
In-Reply-To: <20191226221225.GA800@HATZ>
Aga wrote:
> I do not know if
> you can (or if it is possible, how it can be done), extract with a way a specific
> a functionality from gnulib, with the absolute necessary code and only that.
gnulib-tool does this. With its --avoid option, the developer can even customize
their notion of "absolutely necessary".
> In a myriad of codebases a string type is implemented at least as:
> size_t mem_size;
> size_t num_bytes;
> char *bytes;
This is actually a string-buffer type. A string type does not need two size_t
members. Long-term experience has shown that using different types for string
and string-buffer is a win, because
- a string can be put in a read-only virtual memory area, thus enforcing
immutability (-> reducing multithread problems),
- providing primitives for string allocation reduces the amount of buffer
overflow bugs that otherwise occur in this area. [1]
Unfortunately, the common string type in C is 'char *' with NUL termination,
and a different type is hard to establish
- because developers already know how to use 'char *',
- because existing functions like printf consume 'char *' strings.
- Few programs have had the need to correctly handles strings with embedded
NULs.
> An extended ustring (unicode|utf8) type can include information for its bytes with
> character semantics, like:
> (utf8 typedef'ed as signed int)
> utf8 code; // the integer representation
> int len; // the number of the needed bytes
> int width; // the number of the occupied cells
> char buf[5]; // and probably the character representation
Such a type would have a niche use, IMO, because
- 99% of the processing would not need to access the width (screen columns) - so
why spend CPU time and RAM to store it and keep it up-to-date?
- 80% of the processing does not care about the Unicode code points either,
and libraries like libunistring can do the Unicode-aware processing.
> But the programmer mind would be probably best
> if could concentrate to how to express the thought (with whatever meaning of what we
> are calling "thought") and follow this flow, or if could concentrate the energy to
> understand the intentions (while reading) of the code (instead of wasting self with
> the "details" of the code) and finally to the actual algorithm (usually conditions
> that can or can't be met).
That is the idea behind the container types (list, map) in gnulib. However, I don't
see how to reasonably transpose this principle to string types.
Bruno
[1] https://lists.gnu.org/archive/html/bug-gnulib/2019-09/msg00031.html
next prev parent reply other threads:[~2019-12-27 10:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 13:45 hard-locale: make multithread-safe Bruno Haible
2019-12-17 14:08 ` Tim Rühsen
[not found] ` <20191226221225.GA800@HATZ>
2019-12-27 10:51 ` Bruno Haible [this message]
2019-12-28 13:14 ` string types ag
2019-12-28 18:28 ` Paul Eggert
2019-12-28 20:44 ` ag
2019-12-28 22:40 ` Paul Eggert
2019-12-29 9:19 ` Bruno Haible
2019-12-29 17:13 ` ag
2019-12-29 20:02 ` ag
2019-12-29 21:24 ` Tim Rühsen
2019-12-31 9:53 ` Bruno Haible
2020-01-06 10:34 ` Tim Rühsen
2020-01-06 12:46 ` Bruno Haible
2020-01-06 16:08 ` Tim Rühsen
2020-01-06 16:49 ` Tim Rühsen
2019-12-18 1:45 ` hard-locale: make multithread-safe Paul Eggert
2019-12-18 8:51 ` Bruno Haible
2019-12-21 6:33 ` Bruno Haible
2019-12-18 10:29 ` LC_COLLATE in the C locale Bruno Haible
2019-12-18 16:27 ` Paul Eggert
2019-12-18 10:46 ` hard-locale: make multithread-safe Bruno Haible
2019-12-24 23:36 ` Bruno Haible
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