stdio-common: Add __translated_number_width

This function will be used to compute the width of a number
after i18n digit translation.

3 files changed, 55 insertions, 1 deletions

diff --git a/include/printf.h b/include/printf.h
index 8f064149d3..5127a45f9b 100644
--- a/include/printf.h
+++ b/include/printf.h
@@ -53,7 +53,18 @@ int __wprintf_function_invoke (void *, printf_function callback,
 
 #include <bits/types/locale_t.h>
 
-/* Now define the internal interfaces.  */
+/* Returns the width (as for printf, in bytes) of the converted ASCII
+   number in the characters in the range [FIRST, LAST).  The range
+   must only contain ASCII digits.  The caller is responsible for
+   avoiding overflow.
+
+   This function is used during non-wide digit translation.  Wide
+   digit translate produces one wide character per ASCII digit,
+   so the width is simply LAST - FIRST.  */
+int __translated_number_width (locale_t loc,
+			       const char *first, const char *last)
+  attribute_hidden;
+
 extern int __printf_fphex (FILE *, const struct printf_info *,
 			   const void *const *) attribute_hidden;
 extern int __printf_fp (FILE *, const struct printf_info *,
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 6e6da091b1..3e0c574ca5 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -85,6 +85,7 @@ routines := \
   tmpfile64 \
   tmpnam \
   tmpnam_r \
+  translated_number_width \
   vfprintf \
   vfprintf-internal \
   vfscanf \
diff --git a/stdio-common/translated_number_width.c b/stdio-common/translated_number_width.c
new file mode 100644
index 0000000000..f42d5968a1
--- /dev/null
+++ b/stdio-common/translated_number_width.c
@@ -0,0 +1,42 @@
+/* Compute the printf width of a sequence of ASCII digits.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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 the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <limits.h>
+#include <locale/localeinfo.h>
+#include <printf.h>
+
+int
+__translated_number_width (locale_t loc, const char *first, const char *last)
+{
+  struct lc_ctype_data *ctype = loc->__locales[LC_CTYPE]->private;
+
+  if (ctype->outdigit_bytes_all_equal > 0)
+    return (last - first) * ctype->outdigit_bytes_all_equal;
+  else
+    {
+      /* Digits have varying length, so the fast path cannot be used.  */
+      int digits = 0;
+      for (const char *p = first; p < last; ++p)
+        {
+          assert ('0' <= *p && *p <= '9');
+          digits += ctype->outdigit_bytes[*p - '0'];
+        }
+      return digits;
+    }
+}