Reducing unncessary string copying

[Enrico Weigelt <weigelt metux de>]

Hi folks,


I've observed in many C applications, often compile-time defined
data like strings are copied unnecessarily.

For example, if you pass names to certain objects (eg. opening a
file, creating a window, etc) that will never change of disappear
during the process' lifetime (eg. compiled-in), those strings
dont need to be copied.

Now the big question becomes: how to decide this ?

I'm currently experimenting with a new string reference datatype
that has an extra bit which tells whether the string is static.
Essentially a struct consisting of the char* pointer and an
extra byte for the flag. That struct then will be used instead
of the const char* pointers. A few inline functions handle the
conversion from/to normal const char* and on-demand copying.

Just some theoretical example:

Some function

    FOO* create_foo(const char* name)

now becomes

    FOO* create_foo(GCStr name)

and the call now would be

    create_foo(G_CSTR_STATIC("hello world"));

in case we dont have an "static" string, but something with
limited lifetime, it could look like this:

    create_foo(G_CSTR_DYNAMIC(bar));

Inside create_foo() we'll then replace g_strdup() by some
G_CSTR_COPY() and g_free() by G_CSTR_FREE(). These functions
will know whether the string has to be copied/free'd.


Let's just leave the question of API-compatibility aside,
what do you think about this idea ?



greets
-- 
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 Enrico Weigelt, metux IT service -- http://www.metux.de/

 phone:  +49 36207 519931  email: weigelt metux de
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