lib/unilbrk/u16-width-linebreaks.c

   1 /* Line breaking of UTF-16 strings.
   2    Copyright (C) 2001-2003, 2006-2020 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2001.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU Lesser General Public License as published
   7    by the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "unilbrk.h"
  22
  23 #include "unistr.h"
  24 #include "uniwidth.h"
  25
  26 int
  27 u16_width_linebreaks (const uint16_t *s, size_t n,
  28                       int width, int start_column, int at_end_columns,
  29                       const char *o, const char *encoding,
  30                       char *p)
  31 {
  32   const uint16_t *s_end;
  33   char *last_p;
  34   int last_column;
  35   int piece_width;
  36
  37   u16_possible_linebreaks (s, n, encoding, p);
  38
  39   s_end = s + n;
  40   last_p = NULL;
  41   last_column = start_column;
  42   piece_width = 0;
  43   while (s < s_end)
  44     {
  45       ucs4_t uc;
  46       int count = u16_mbtouc_unsafe (&uc, s, s_end - s);
  47
  48       /* Respect the override.  */
  49       if (o != NULL && *o != UC_BREAK_UNDEFINED)
  50         *p = *o;
  51
  52       if (*p == UC_BREAK_POSSIBLE || *p == UC_BREAK_MANDATORY)
  53         {
  54           /* An atomic piece of text ends here.  */
  55           if (last_p != NULL && last_column + piece_width > width)
  56             {
  57               /* Insert a line break.  */
  58               *last_p = UC_BREAK_POSSIBLE;
  59               last_column = 0;
  60             }
  61         }
  62
  63       if (*p == UC_BREAK_MANDATORY)
  64         {
  65           /* uc is a line break character.  */
  66           /* Start a new piece at column 0.  */
  67           last_p = NULL;
  68           last_column = 0;
  69           piece_width = 0;
  70         }
  71       else
  72         {
  73           /* uc is not a line break character.  */
  74           int w;
  75
  76           if (*p == UC_BREAK_POSSIBLE)
  77             {
  78               /* Start a new piece.  */
  79               last_p = p;
  80               last_column += piece_width;
  81               piece_width = 0;
  82               /* No line break for the moment, may be turned into
  83                  UC_BREAK_POSSIBLE later, via last_p. */
  84             }
  85
  86           *p = UC_BREAK_PROHIBITED;
  87
  88           w = uc_width (uc, encoding);
  89           if (w >= 0) /* ignore control characters in the string */
  90             piece_width += w;
  91         }
  92
  93       s += count;
  94       p += count;
  95       if (o != NULL)
  96         o += count;
  97     }
  98
  99   /* The last atomic piece of text ends here.  */
 100   if (last_p != NULL && last_column + piece_width + at_end_columns > width)
 101     {
 102       /* Insert a line break.  */
 103       *last_p = UC_BREAK_POSSIBLE;
 104       last_column = 0;
 105     }
 106
 107   return last_column + piece_width;
 108 }