contrib/diffutils/lib/mbuiter.h

   1 /* Iterating through multibyte strings: macros for multi-byte encodings.
   2    Copyright (C) 2001, 2005, 2007, 2009-2013 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>.  */
  18
  19 /* The macros in this file implement forward iteration through a
  20    multi-byte string, without knowing its length a-priori.
  21
  22    With these macros, an iteration loop that looks like
  23
  24       char *iter;
  25       for (iter = buf; *iter != '\0'; iter++)
  26         {
  27           do_something (*iter);
  28         }
  29
  30    becomes
  31
  32       mbui_iterator_t iter;
  33       for (mbui_init (iter, buf); mbui_avail (iter); mbui_advance (iter))
  34         {
  35           do_something (mbui_cur_ptr (iter), mb_len (mbui_cur (iter)));
  36         }
  37
  38    The benefit of these macros over plain use of mbrtowc is:
  39    - Handling of invalid multibyte sequences is possible without
  40      making the code more complicated, while still preserving the
  41      invalid multibyte sequences.
  42
  43    Compared to mbiter.h, the macros here don't need to know the string's
  44    length a-priori.  The downside is that at each step, the look-ahead
  45    that guards against overrunning the terminating '\0' is more expensive.
  46    The mbui_* macros are therefore suitable when there is a high probability
  47    that only the first few multibyte characters need to be inspected.
  48    Whereas the mbi_* macros are better if usually the iteration runs
  49    through the entire string.
  50
  51    mbui_iterator_t
  52      is a type usable for variable declarations.
  53
  54    mbui_init (iter, startptr)
  55      initializes the iterator, starting at startptr.
  56
  57    mbui_avail (iter)
  58      returns true if there are more multibyte characters available before
  59      the end of string is reached. In this case, mbui_cur (iter) is
  60      initialized to the next multibyte character.
  61
  62    mbui_advance (iter)
  63      advances the iterator by one multibyte character.
  64
  65    mbui_cur (iter)
  66      returns the current multibyte character, of type mbchar_t.  All the
  67      macros defined in mbchar.h can be used on it.
  68
  69    mbui_cur_ptr (iter)
  70      return a pointer to the beginning of the current multibyte character.
  71
  72    mbui_reloc (iter, ptrdiff)
  73      relocates iterator when the string is moved by ptrdiff bytes.
  74
  75    mbui_copy (&destiter, &srciter)
  76      copies srciter to destiter.
  77
  78    Here are the function prototypes of the macros.
  79
  80    extern void          mbui_init (mbui_iterator_t iter, const char *startptr);
  81    extern bool          mbui_avail (mbui_iterator_t iter);
  82    extern void          mbui_advance (mbui_iterator_t iter);
  83    extern mbchar_t      mbui_cur (mbui_iterator_t iter);
  84    extern const char *  mbui_cur_ptr (mbui_iterator_t iter);
  85    extern void          mbui_reloc (mbui_iterator_t iter, ptrdiff_t ptrdiff);
  86    extern void          mbui_copy (mbui_iterator_t *new, const mbui_iterator_t *old);
  87  */
  88
  89 #ifndef _MBUITER_H
  90 #define _MBUITER_H 1
  91
  92 #include <assert.h>
  93 #include <stdbool.h>
  94 #include <stddef.h>
  95 #include <stdlib.h>
  96 #include <string.h>
  97
  98 /* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
  99    <wchar.h>.
 100    BSD/OS 4.1 has a bug: <stdio.h> and <time.h> must be included before
 101    <wchar.h>.  */
 102 #include <stdio.h>
 103 #include <time.h>
 104 #include <wchar.h>
 105
 106 #include "mbchar.h"
 107 #include "strnlen1.h"
 108
 109 _GL_INLINE_HEADER_BEGIN
 110 #ifndef MBUITER_INLINE
 111 # define MBUITER_INLINE _GL_INLINE
 112 #endif
 113
 114 struct mbuiter_multi
 115 {
 116   bool in_shift;        /* true if next byte may not be interpreted as ASCII */
 117   mbstate_t state;      /* if in_shift: current shift state */
 118   bool next_done;       /* true if mbui_avail has already filled the following */
 119   struct mbchar cur;    /* the current character:
 120         const char *cur.ptr             pointer to current character
 121         The following are only valid after mbui_avail.
 122         size_t cur.bytes                number of bytes of current character
 123         bool cur.wc_valid               true if wc is a valid wide character
 124         wchar_t cur.wc                  if wc_valid: the current character
 125         */
 126 };
 127
 128 MBUITER_INLINE void
 129 mbuiter_multi_next (struct mbuiter_multi *iter)
 130 {
 131   if (iter->next_done)
 132     return;
 133   if (iter->in_shift)
 134     goto with_shift;
 135   /* Handle most ASCII characters quickly, without calling mbrtowc().  */
 136   if (is_basic (*iter->cur.ptr))
 137     {
 138       /* These characters are part of the basic character set.  ISO C 99
 139          guarantees that their wide character code is identical to their
 140          char code.  */
 141       iter->cur.bytes = 1;
 142       iter->cur.wc = *iter->cur.ptr;
 143       iter->cur.wc_valid = true;
 144     }
 145   else
 146     {
 147       assert (mbsinit (&iter->state));
 148       iter->in_shift = true;
 149     with_shift:
 150       iter->cur.bytes = mbrtowc (&iter->cur.wc, iter->cur.ptr,
 151                                  strnlen1 (iter->cur.ptr, MB_CUR_MAX),
 152                                  &iter->state);
 153       if (iter->cur.bytes == (size_t) -1)
 154         {
 155           /* An invalid multibyte sequence was encountered.  */
 156           iter->cur.bytes = 1;
 157           iter->cur.wc_valid = false;
 158           /* Whether to set iter->in_shift = false and reset iter->state
 159              or not is not very important; the string is bogus anyway.  */
 160         }
 161       else if (iter->cur.bytes == (size_t) -2)
 162         {
 163           /* An incomplete multibyte character at the end.  */
 164           iter->cur.bytes = strlen (iter->cur.ptr);
 165           iter->cur.wc_valid = false;
 166           /* Whether to set iter->in_shift = false and reset iter->state
 167              or not is not important; the string end is reached anyway.  */
 168         }
 169       else
 170         {
 171           if (iter->cur.bytes == 0)
 172             {
 173               /* A null wide character was encountered.  */
 174               iter->cur.bytes = 1;
 175               assert (*iter->cur.ptr == '\0');
 176               assert (iter->cur.wc == 0);
 177             }
 178           iter->cur.wc_valid = true;
 179
 180           /* When in the initial state, we can go back treating ASCII
 181              characters more quickly.  */
 182           if (mbsinit (&iter->state))
 183             iter->in_shift = false;
 184         }
 185     }
 186   iter->next_done = true;
 187 }
 188
 189 MBUITER_INLINE void
 190 mbuiter_multi_reloc (struct mbuiter_multi *iter, ptrdiff_t ptrdiff)
 191 {
 192   iter->cur.ptr += ptrdiff;
 193 }
 194
 195 MBUITER_INLINE void
 196 mbuiter_multi_copy (struct mbuiter_multi *new_iter, const struct mbuiter_multi *old_iter)
 197 {
 198   if ((new_iter->in_shift = old_iter->in_shift))
 199     memcpy (&new_iter->state, &old_iter->state, sizeof (mbstate_t));
 200   else
 201     memset (&new_iter->state, 0, sizeof (mbstate_t));
 202   new_iter->next_done = old_iter->next_done;
 203   mb_copy (&new_iter->cur, &old_iter->cur);
 204 }
 205
 206 /* Iteration macros.  */
 207 typedef struct mbuiter_multi mbui_iterator_t;
 208 #define mbui_init(iter, startptr) \
 209   ((iter).cur.ptr = (startptr), \
 210    (iter).in_shift = false, memset (&(iter).state, '\0', sizeof (mbstate_t)), \
 211    (iter).next_done = false)
 212 #define mbui_avail(iter) \
 213   (mbuiter_multi_next (&(iter)), !mb_isnul ((iter).cur))
 214 #define mbui_advance(iter) \
 215   ((iter).cur.ptr += (iter).cur.bytes, (iter).next_done = false)
 216
 217 /* Access to the current character.  */
 218 #define mbui_cur(iter) (iter).cur
 219 #define mbui_cur_ptr(iter) (iter).cur.ptr
 220
 221 /* Relocation.  */
 222 #define mbui_reloc(iter, ptrdiff) mbuiter_multi_reloc (&iter, ptrdiff)
 223
 224 /* Copying an iterator.  */
 225 #define mbui_copy mbuiter_multi_copy
 226
 227 _GL_INLINE_HEADER_END
 228
 229 #endif /* _MBUITER_H */