lib/readtokens0.c

   1 /* readtokens0.c -- Read NUL-separated tokens from an input stream.
   2
   3    Copyright (C) 2004, 2006, 2009-2024 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.
  17
  18    Written by Jim Meyering. */
  19
  20 #include <config.h>
  21
  22 #include <stdlib.h>
  23
  24 #include "readtokens0.h"
  25
  26 #define obstack_chunk_alloc malloc
  27 #define obstack_chunk_free free
  28
  29 void
  30 readtokens0_init (struct Tokens *t)
  31 {
  32   t->n_tok = 0;
  33   t->tok = NULL;
  34   t->tok_len = NULL;
  35   obstack_init (&t->o_data);
  36   obstack_init (&t->o_tok);
  37   obstack_init (&t->o_tok_len);
  38 }
  39
  40 void
  41 readtokens0_free (struct Tokens *t)
  42 {
  43   obstack_free (&t->o_data, NULL);
  44   obstack_free (&t->o_tok, NULL);
  45   obstack_free (&t->o_tok_len, NULL);
  46 }
  47
  48 /* Finalize (in the obstack_finish sense) the current token
  49    and record its pointer and length.  */
  50 static void
  51 save_token (struct Tokens *t)
  52 {
  53   /* Don't count the trailing NUL byte in the length.  */
  54   size_t len = obstack_object_size (&t->o_data) - 1;
  55   char const *s = obstack_finish (&t->o_data);
  56   obstack_ptr_grow (&t->o_tok, s);
  57   obstack_grow (&t->o_tok_len, &len, sizeof len);
  58   t->n_tok++;
  59 }
  60
  61 /* Read NUL-separated tokens from stream IN into T until EOF or error.
  62    The final NUL is optional.  Always append a NULL pointer to the
  63    resulting list of token pointers, but that pointer isn't counted
  64    via t->n_tok.  Return true if successful.  */
  65 bool
  66 readtokens0 (FILE *in, struct Tokens *t)
  67 {
  68
  69   while (1)
  70     {
  71       int c = fgetc (in);
  72       if (c == EOF)
  73         {
  74           size_t len = obstack_object_size (&t->o_data);
  75           /* If the current object has nonzero length, then there
  76              was no NUL byte at EOF -- or maybe there was an error,
  77              in which case, we need to append a NUL byte to our buffer.  */
  78           if (len)
  79             {
  80               obstack_1grow (&t->o_data, '\0');
  81               save_token (t);
  82             }
  83
  84           break;
  85         }
  86
  87       obstack_1grow (&t->o_data, c);
  88       if (c == '\0')
  89         save_token (t);
  90     }
  91
  92   /* Add a NULL pointer at the end, in case the caller (like du)
  93      requires an argv-style array of strings.  */
  94   obstack_ptr_grow (&t->o_tok, NULL);
  95
  96   t->tok = obstack_finish (&t->o_tok);
  97   t->tok_len = obstack_finish (&t->o_tok_len);
  98   return ! ferror (in);
  99 }