1 files changed, 116 insertions, 0 deletions
diff --git a/lib/unistring/uninorm/canonical-decomposition.c b/lib/unistring/uninorm/canonical-decomposition.c
new file mode 100644
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+++ b/lib/unistring/uninorm/canonical-decomposition.c
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+/* Canonical decomposition of Unicode characters.
+   Copyright (C) 2009-2021 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 either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+   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
+   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 "uninorm.h"
+
+#include <stdlib.h>
+
+#include "uninorm/decomposition-table.h"
+
+int
+uc_canonical_decomposition (ucs4_t uc, ucs4_t *decomposition)
+{
+  if (uc >= 0xAC00 && uc < 0xD7A4)
+    {
+      /* Hangul syllable.  See Unicode standard, chapter 3, section
+         "Hangul Syllable Decomposition",  See also the clarification at
+         <https://www.unicode.org/versions/Unicode5.1.0/>, section
+         "Clarification of Hangul Jamo Handling".  */
+      unsigned int t;
+
+      uc -= 0xAC00;
+      t = uc % 28;
+
+      if (t == 0)
+        {
+          unsigned int v, l;
+
+          uc = uc / 28;
+          v = uc % 21;
+          l = uc / 21;
+
+          decomposition[0] = 0x1100 + l;
+          decomposition[1] = 0x1161 + v;
+          return 2;
+        }
+      else
+        {
+#if 1 /* Return the pairwise decomposition, not the full decomposition.  */
+          decomposition[0] = 0xAC00 + uc - t; /* = 0xAC00 + (l * 21 + v) * 28; */
+          decomposition[1] = 0x11A7 + t;
+          return 2;
+#else
+          unsigned int v, l;
+
+          uc = uc / 28;
+          v = uc % 21;
+          l = uc / 21;
+
+          decomposition[0] = 0x1100 + l;
+          decomposition[1] = 0x1161 + v;
+          decomposition[2] = 0x11A7 + t;
+          return 3;
+#endif
+        }
+    }
+  else if (uc < 0x110000)
+    {
+      unsigned short entry = decomp_index (uc);
+      /* An entry of (unsigned short)(-1) denotes an absent entry.
+         Otherwise, bit 15 of the entry tells whether the decomposition
+         is a canonical one.  */
+      if (entry < 0x8000)
+        {
+          const unsigned char *p;
+          unsigned int element;
+          unsigned int length;
+
+          p = &gl_uninorm_decomp_chars_table[3 * entry];
+          element = (p[0] << 16) | (p[1] << 8) | p[2];
+          /* The first element has 5 bits for the decomposition type.  */
+          if (((element >> 18) & 0x1f) != UC_DECOMP_CANONICAL)
+            abort ();
+          length = 1;
+          for (;;)
+            {
+              /* Every element has an 18 bits wide Unicode code point.  */
+              *decomposition = element & 0x3ffff;
+              /* Bit 23 tells whether there are more elements,  */
+              if ((element & (1 << 23)) == 0)
+                break;
+              p += 3;
+              element = (p[0] << 16) | (p[1] << 8) | p[2];
+              decomposition++;
+              length++;
+            }
+          return length;
+        }
+    }
+  return -1;
+}