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diff --git a/lib/unicase/context.h b/lib/unicase/context.h
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+/* Case-mapping contexts of UTF-8/UTF-16/UTF-32 substring.
+   Copyright (C) 2009-2020 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2009.
+
+   This program is free software: you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+
+/* The context of a prefix string combines the information of the "Before C"
+   conditions of the Unicode Standard,
+   <https://www.unicode.org/versions/Unicode5.0.0/ch03.pdf>, section 3.13,
+   table 3-14 "Context Specification for Casing".
+
+   casing_prefix_context_t contains the following fields:
+
+     // Helper for evaluating the FINAL_SIGMA condition:
+     //  Last character that was not case-ignorable.
+     ucs4_t last_char_except_ignorable;
+
+     // Helper for evaluating the AFTER_SOFT_DOTTED and AFTER_I conditions:
+     // Last character that was of combining class 230 ("Above") or 0.
+     ucs4_t last_char_normal_or_above;
+
+   Three bits would be sufficient to carry the context information, but
+   that would require to invoke uc_is_cased and uc_is_property_soft_dotted
+   ahead of time, more often than actually needed.  */
+
+
+/* The context of a suffix string combines the information of the "After C"
+   conditions of the Unicode Standard,
+   <https://www.unicode.org/versions/Unicode5.0.0/ch03.pdf>, section 3.13,
+   table 3-14 "Context Specification for Casing".
+
+   casing_suffix_context_t contains the following fields:
+
+     // For evaluating the FINAL_SIGMA condition:
+     //  First character that was not case-ignorable.
+     ucs4_t first_char_except_ignorable;
+
+     // For evaluating the MORE_ABOVE condition:
+     // Bit 0 is set if the suffix contains a character of combining class
+     // 230 (Above) with no character of combining class 0 or 230 (Above)
+     // before it.
+     //
+     // For evaluating the BEFORE_DOT condition:
+     // Bit 1 is set if the suffix contains a COMBINING DOT ABOVE (U+0307)
+     // with no character of combining class 0 or 230 (Above) before it.
+     //
+     uint32_t bits;
+
+   Three bits would be sufficient to carry the context information, but
+   that would require to invoke uc_is_cased ahead of time, more often than
+   actually needed.  */
+#define SCC_MORE_ABOVE_MASK  1
+#define SCC_BEFORE_DOT_MASK  2