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path: root/src/locale/newlocale.c
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#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include "locale_impl.h"

static pthread_once_t default_locale_once;
static struct __locale_struct default_locale, default_ctype_locale;

static void default_locale_init(void)
{
	for (int i=0; i<LC_ALL; i++)
		default_locale.cat[i] = __get_locale(i, "");
	default_ctype_locale.cat[LC_CTYPE] = default_locale.cat[LC_CTYPE];
}

int __loc_is_allocated(locale_t loc)
{
	return loc && loc != C_LOCALE && loc != UTF8_LOCALE
		&& loc != &default_locale && loc != &default_ctype_locale;
}

locale_t __newlocale(int mask, const char *name, locale_t loc)
{
	struct __locale_struct tmp;

	for (int i=0; i<LC_ALL; i++) {
		tmp.cat[i] = (!(mask & (1<<i)) && loc) ? loc->cat[i] :
			__get_locale(i, (mask & (1<<i)) ? name : "");
		if (tmp.cat[i] == LOC_MAP_FAILED)
			return 0;
	}

	/* For locales with allocated storage, modify in-place. */
	if (__loc_is_allocated(loc)) {
		*loc = tmp;
		return loc;
	}

	/* Otherwise, first see if we can use one of the builtin locales.
	 * This makes the common usage case for newlocale, getting a C locale
	 * with predictable behavior, very fast, and more importantly, fail-safe. */
	if (!memcmp(&tmp, C_LOCALE, sizeof tmp)) return C_LOCALE;
	if (!memcmp(&tmp, UTF8_LOCALE, sizeof tmp)) return UTF8_LOCALE;

	/* And provide builtins for the initial default locale, and a
	 * variant of the C locale honoring the default locale's encoding. */
	pthread_once(&default_locale_once, default_locale_init);
	if (!memcmp(&tmp, &default_locale, sizeof tmp)) return &default_locale;
	if (!memcmp(&tmp, &default_ctype_locale, sizeof tmp))
		return &default_ctype_locale;

	/* If no builtin locale matched, attempt to allocate and copy. */
	if ((loc = malloc(sizeof *loc))) *loc = tmp;

	return loc;
}

weak_alias(__newlocale, newlocale);