lib/obstack_printf.c

   1 /* Formatted output to obstacks.
   2    Copyright (C) 2008-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published
   6    by the Free Software Foundation, either version 3 of the License,
   7    or (at your option) any later version.
   8
   9    This file 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 <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <stdio.h>
  21
  22 #include "obstack.h"
  23 #include "vasnprintf.h"
  24
  25 #include <errno.h>
  26 #include <stdarg.h>
  27 #include <stdlib.h>
  28
  29 /* Grow an obstack with formatted output.  Return the number of bytes
  30    added to OBS.  No trailing nul byte is added, and the object should
  31    be closed with obstack_finish before use.
  32
  33    Upon memory allocation error, call obstack_alloc_failed_handler.
  34    Upon other error, return -1.  */
  35 int
  36 obstack_printf (struct obstack *obs, const char *format, ...)
  37 {
  38   va_list args;
  39   int result;
  40
  41   va_start (args, format);
  42   result = obstack_vprintf (obs, format, args);
  43   va_end (args);
  44   return result;
  45 }
  46
  47 /* Grow an obstack with formatted output.  Return the number of bytes
  48    added to OBS.  No trailing nul byte is added, and the object should
  49    be closed with obstack_finish before use.
  50
  51    Upon memory allocation error, call obstack_alloc_failed_handler.
  52    Upon other error, return -1.  */
  53 int
  54 obstack_vprintf (struct obstack *obs, const char *format, va_list args)
  55 {
  56   /* If we are close to the end of the current obstack chunk, use a
  57      stack-allocated buffer and copy, to reduce the likelihood of a
  58      small-size malloc.  Otherwise, print directly into the
  59      obstack.  */
  60   enum { CUTOFF = 1024 };
  61   char buf[CUTOFF];
  62   char *base = obstack_next_free (obs);
  63   size_t len = obstack_room (obs);
  64   char *str;
  65
  66   if (len < CUTOFF)
  67     {
  68       base = buf;
  69       len = CUTOFF;
  70     }
  71   str = vasnprintf (base, &len, format, args);
  72   if (!str)
  73     {
  74       if (errno == ENOMEM)
  75         obstack_alloc_failed_handler ();
  76       return -1;
  77     }
  78   if (str == base && str != buf)
  79     /* The output was already computed in place, but we need to
  80        account for its size.  */
  81     obstack_blank_fast (obs, len);
  82   else
  83     {
  84       /* The output exceeded available obstack space or we used buf;
  85          copy the resulting string.  */
  86       obstack_grow (obs, str, len);
  87       if (str != buf)
  88         free (str);
  89     }
  90   return len;
  91 }