1 files changed, 102 insertions, 0 deletions
diff --git a/lib/c32width.c b/lib/c32width.c
new file mode 100644
index 0000000000..4149e06b25
--- /dev/null
+++ b/lib/c32width.c
@@ -0,0 +1,102 @@
+/* Determine the number of screen columns needed for a 32-bit wide character.
+   Copyright (C) 2020-2023 Free Software Foundation, Inc.
+
+   This file is free software.
+   It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+".
+   You can redistribute it and/or modify it under either
+     - the terms of the GNU Lesser General Public License as published
+       by the Free Software Foundation, either version 3, or (at your
+       option) any later version, or
+     - the terms of the GNU General Public License as published by the
+       Free Software Foundation; either version 2, or (at your option)
+       any later version, or
+     - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+".
+
+   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 and the GNU General Public License
+   for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License and of the GNU General Public License along with this
+   program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2023.  */
+
+#include <config.h>
+
+#define IN_C32WIDTH
+/* Specification.  */
+#include <uchar.h>
+
+#include <wchar.h>
+
+#ifdef __CYGWIN__
+# include <cygwin/version.h>
+#endif
+
+#if GNULIB_defined_mbstate_t
+# include "streq.h"
+#endif
+
+#include "localcharset.h"
+#include "uniwidth.h"
+
+#if _GL_WCHAR_T_IS_UCS4 && !GNULIB_defined_mbstate_t
+_GL_EXTERN_INLINE
+#endif
+int
+c32width (char32_t wc)
+{
+  /* The char32_t encoding of a multibyte character is defined by the way
+     mbrtoc32() is defined.  */
+
+#if GNULIB_defined_mbstate_t            /* AIX, IRIX */
+  /* mbrtoc32() is defined on top of mbtowc() for the non-UTF-8 locales
+     and directly for the UTF-8 locales.  */
+  const char *encoding = locale_charset ();
+  if (STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0))
+    return uc_width (wc, encoding);
+  else
+    return wcwidth (wc);
+
+#elif HAVE_WORKING_MBRTOC32             /* glibc */
+  /* mbrtoc32() is essentially defined by the system libc.  */
+
+# if _GL_WCHAR_T_IS_UCS4
+  /* The char32_t encoding of a multibyte character is known to be the same as
+     the wchar_t encoding.  */
+  return wcwidth (wc);
+# else
+  /* The char32_t encoding of a multibyte character is known to be UCS-4,
+     different from the wchar_t encoding.  */
+  return uc_width (wc, locale_charset ());
+# endif
+
+#elif _GL_SMALL_WCHAR_T                 /* Cygwin, mingw, MSVC */
+  /* The wchar_t encoding is UTF-16.
+     The char32_t encoding is UCS-4.  */
+
+# if defined __CYGWIN__ && CYGWIN_VERSION_DLL_MAJOR >= 1007 && 0
+  /* As an extension to POSIX, the wcwidth() function of Cygwin >= 1.7
+     supports also wc arguments outside the Unicode BMP, that is, outside
+     the 'wchar_t' range.  See
+     <https://www.cygwin.com/cgit/newlib-cygwin/commit/?id=098a75dc51caa98f369d98a9809d773bc45329aa>.
+     But the resulting values for these characters are not of good quality.  */
+  return wcwidth (wc);
+# else
+  if (wc == (wchar_t) wc)
+    /* wc is in the range for the wcwidth function.  */
+    return wcwidth (wc);
+  else
+    return uc_width (wc, locale_charset ());
+# endif
+
+#else /* macOS, FreeBSD, NetBSD, OpenBSD, HP-UX, Solaris, Minix, Android */
+  /* char32_t and wchar_t are equivalent.  */
+  static_assert (sizeof (char32_t) == sizeof (wchar_t));
+
+  return wcwidth (wc);
+#endif
+}