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-rw-r--r--lib/wcwidth.c73
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+/* Determine the number of screen columns needed for a character.
+ Copyright (C) 2006-2007, 2010-2023 Free Software Foundation, Inc.
+
+ This file is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ This file is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include <wchar.h>
+
+/* Get iswprint. */
+#include <wctype.h>
+
+#include "localcharset.h"
+#include "streq.h"
+#include "uniwidth.h"
+
+/* Returns 1 if the current locale is an UTF-8 locale, 0 otherwise. */
+static inline int
+is_locale_utf8 (void)
+{
+ const char *encoding = locale_charset ();
+ return STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0);
+}
+
+#if GNULIB_WCHAR_SINGLE_LOCALE
+/* When we know that the locale does not change, provide a speedup by
+ caching the value of is_locale_utf8. */
+static int cached_is_locale_utf8 = -1;
+static inline int
+is_locale_utf8_cached (void)
+{
+ if (cached_is_locale_utf8 < 0)
+ cached_is_locale_utf8 = is_locale_utf8 ();
+ return cached_is_locale_utf8;
+}
+#else
+/* By default, don't make assumptions, hence no caching. */
+# define is_locale_utf8_cached is_locale_utf8
+#endif
+
+int
+wcwidth (wchar_t wc)
+#undef wcwidth
+{
+ /* In UTF-8 locales, use a Unicode aware width function. */
+ if (is_locale_utf8_cached ())
+ {
+ /* We assume that in a UTF-8 locale, a wide character is the same as a
+ Unicode character. */
+ return uc_width (wc, "UTF-8");
+ }
+ else
+ {
+ /* Otherwise, fall back to the system's wcwidth function. */
+#if HAVE_WCWIDTH
+ return wcwidth (wc);
+#else
+ return wc == 0 ? 0 : iswprint (wc) ? 1 : -1;
+#endif
+ }
+}