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 #ifndef RESULT_TYPE
  30 # define RESULT_TYPE int
  31 # define OBSTACK_PRINTF obstack_printf
  32 # define OBSTACK_VPRINTF obstack_vprintf
  33 #endif
  34
  35 /* Grow an obstack with formatted output.  Return the number of bytes
  36    added to OBS.  No trailing nul byte is added, and the object should
  37    be closed with obstack_finish before use.
  38
  39    Upon memory allocation error, call obstack_alloc_failed_handler.
  40    Upon other error, return -1.  */
  41 RESULT_TYPE
  42 OBSTACK_PRINTF (struct obstack *obs, const char *format, ...)
  43 {
  44   va_list args;
  45   RESULT_TYPE result;
  46
  47   va_start (args, format);
  48   result = OBSTACK_VPRINTF (obs, format, args);
  49   va_end (args);
  50   return result;
  51 }
  52
  53 /* Grow an obstack with formatted output.  Return the number of bytes
  54    added to OBS.  No trailing nul byte is added, and the object should
  55    be closed with obstack_finish before use.
  56
  57    Upon memory allocation error, call obstack_alloc_failed_handler.
  58    Upon other error, return -1.  */
  59 RESULT_TYPE
  60 OBSTACK_VPRINTF (struct obstack *obs, const char *format, va_list args)
  61 {
  62   /* If we are close to the end of the current obstack chunk, use a
  63      stack-allocated buffer and copy, to reduce the likelihood of a
  64      small-size malloc.  Otherwise, print directly into the
  65      obstack.  */
  66   enum { CUTOFF = 1024 };
  67   char buf[CUTOFF];
  68   char *base = obstack_next_free (obs);
  69   size_t len = obstack_room (obs);
  70   char *str;
  71
  72   if (len < CUTOFF)
  73     {
  74       base = buf;
  75       len = CUTOFF;
  76     }
  77   str = vasnprintf (base, &len, format, args);
  78   if (!str)
  79     {
  80       if (errno == ENOMEM)
  81         obstack_alloc_failed_handler ();
  82       return -1;
  83     }
  84   if (str == base && str != buf)
  85     /* The output was already computed in place, but we need to
  86        account for its size.  */
  87     obstack_blank_fast (obs, len);
  88   else
  89     {
  90       /* The output exceeded available obstack space or we used buf;
  91          copy the resulting string.  */
  92       obstack_grow (obs, str, len);
  93       if (str != buf)
  94         free (str);
  95     }
  96   return len;
  97 }