SDL_strcasecmp (even when calling into a C runtime) does not work with
Unicode chars, and depending on the user's locale, might not work with
even basic ASCII strings.
This implements the function from scratch, using "case-folding,"
which is a more robust method that deals with various languages. It
involves a hashtable of a few hundred codepoints that are "uppercase" and
how to map them to lowercase equivalents (possibly increasing the size of
the string in the process). The vast majority of human languages (and
Unicode) do not have letters with different cases, but still, this static
table takes about 10 kilobytes on a 64-bit machine.
Even this will fail in one known case: the Turkish 'i' folds differently
if you're writing in Turkish vs other languages. Generally this is seen as
unfortunate collateral damage in cases where you can't specify the language
in use.
In addition to case-folding the codepoints, the new functions also know how
to decode the various formats to turn them into codepoints in the first
place, instead of blindly stepping by one byte (or one wchar_t) per
character.
Also included is casefolding.txt from the Unicode Consortium and a perl
script to generate the hashtable from that text file, so we can trivially
update this if new languages are added in the future.
A simple test using the new function:
```c
#include <SDL3/SDL.h>
int main(void)
{
const char *a = "α ε η";
const char *b = "Α Ε Η";
SDL_Log(" strcasecmp(\"%s\", \"%s\") == %d\n", a, b, strcasecmp(a, b));
SDL_Log("SDL_strcasecmp(\"%s\", \"%s\") == %d\n", a, b, SDL_strcasecmp(a, b));
return 0;
}
```
Produces:
```
INFO: strcasecmp("α ε η", "Α Ε Η") == 32
INFO: SDL_strcasecmp("α ε η", "Α Ε Η") == 0
```
glibc strcasecmp() fails to compare a Greek lowercase string to its uppercase
equivalent, even with a UTF-8 locale, but SDL_strcasecmp() works.
Other SDL_stdinc.h functions are changed to be more consistent, which is to
say they now ignore any C runtime and often dictate that only English-based
low-ASCII works with them.
Fixes Issue #9313.
- SDL_RWops is now an opaque struct.
- SDL_AllocRW is gone. If an app is creating a custom RWops, they pass the
function pointers to SDL_CreateRW(), which are stored internally.
- SDL_RWclose is gone, there is only SDL_DestroyRW(), which calls the
implementation's `->close` method before freeing other things.
- There is only one path to create and use RWops now, so we don't have to
worry about whether `->close` will call SDL_DestroyRW, or if this will
risk any Properties not being released, etc.
- SDL_RWFrom* still works as expected, for getting a RWops without having
to supply your own implementation. Objects from these functions are also
destroyed with SDL_DestroyRW.
- Lots of other cleanup and SDL3ization of the library code.
Frank Praznik
Petar Popovic
Sam Lantinga
Ryan C. Gordon
Mirko Galimberti
Cameron Gutman
SDL Wiki Bot
Susko3
Anonymous Maarten