locale: Implement struct grouping_iterator

The iterator allows grouping while scanning forward through
the digits.  This enables emitting digits as they are processed.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/stdio-common/grouping_iterator.h b/stdio-common/grouping_iterator.h
new file mode 100644
index 0000000000..e9fc79f616
--- /dev/null
+++ b/stdio-common/grouping_iterator.h
@@ -0,0 +1,65 @@
+/* Iterator for grouping a number while scanning it forward.
+   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/>.  */
+
+#ifndef GROUPING_ITERATOR_H
+#define GROUPING_ITERATOR_H
+
+#include <locale.h>
+#include <stdbool.h>
+
+struct grouping_iterator
+{
+  /* Number of characters in the current group.  If this reaches zero,
+     a thousands separator needs to be emittted.  */
+  unsigned int remaining_in_current_group;
+
+  /* Number of characters remaining in the number.  This is used to
+     detect the start of the non-repeating groups.  */
+  unsigned int remaining;
+
+  /* Points to the current grouping descriptor.  */
+  const char *groupings;
+
+  /* Total number of characters in the non-repeating groups.  */
+  unsigned int non_repeating_groups;
+
+  /* Number of separators that will be inserted if the whole number is
+     processed.  (Does not change during iteration.)  */
+  unsigned int separators;
+};
+
+struct __locale_data;
+
+/* Initializes *IT with the data from LOCDATA (which must be for
+   LC_MONETARY or LC_NUMERIC).  DIGITS is the length of the number.
+   Returns true if grouping is active, false if not.  */
+bool __grouping_iterator_init (struct grouping_iterator *it,
+                               int category, locale_t loc,
+                               unsigned int digits) attribute_hidden;
+
+/* Initializes *IT with no grouping information for a string of length
+   DIGITS, and return false to indicate no grouping.  */
+bool __grouping_iterator_init_none (struct grouping_iterator *it,
+                                    unsigned int digits)
+  attribute_hidden;
+
+/* Advances to the next character and returns true if a thousands
+   separator should be inserted before emitting it.  */
+bool __grouping_iterator_next (struct grouping_iterator *it);
+
+#endif /* GROUPING_ITERATOR_H */