/* Canonical decomposition of Unicode characters.

   Copyright (C) 2009-2026 Free Software Foundation, Inc.

   Written by Bruno Haible <bruno@clisp.org>, 2009.

   This file 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.

   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 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".  */

      uc -= 0xAC00;

      unsigned int t = uc % 28;

      if (t == 0)

        {

          uc = uc / 28;

          unsigned int v = uc % 21;

          unsigned int 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

          uc = uc / 28;

          unsigned int v = uc % 21;

          unsigned int 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 = &gl_uninorm_decomp_chars_table[3 * entry];

          unsigned int 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 ();

          unsigned int 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;

}