/* Decomposition of Unicode characters.
   Copyright (C) 2009 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 Lesser 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
   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 <http://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */
#include "uninorm.h"

#include "decomposition-table.h"

int
uc_decomposition (ucs4_t uc, int *decomp_tag, ucs4_t *decomposition)
{
  if (uc >= 0xAC00 && uc < 0xD7A4)
    {
      /* Hangul syllable.  See Unicode standard, chapter 3, section
         "Hangul Syllable Decomposition",  See also the clarification at
	 <http://www.unicode.org/versions/Unicode5.1.0/>, section
	 "Clarification of Hangul Jamo Handling".  */
      unsigned int t;

      uc -= 0xAC00;
      t = uc % 28;

      *decomp_tag = UC_DECOMP_CANONICAL;
      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);
      if (entry != (unsigned short)(-1))
	{
	  const unsigned char *p;
	  unsigned int element;
	  unsigned int length;

	  p = &gl_uninorm_decomp_chars_table[3 * (entry & 0x7FFF)];
	  element = (p[0] << 16) | (p[1] << 8) | p[2];
	  /* The first element has 5 bits for the decomposition type.  */
	  *decomp_tag = (element >> 18) & 0x1f;
	  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;
}