libio/vasprintf.c

   1 /* Copyright (C) 1995-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.
  17
  18    As a special exception, if you link the code in this file with
  19    files compiled with a GNU compiler to produce an executable,
  20    that does not cause the resulting executable to be covered by
  21    the GNU Lesser General Public License.  This exception does not
  22    however invalidate any other reasons why the executable file
  23    might be covered by the GNU Lesser General Public License.
  24    This exception applies to code released by its copyright holders
  25    in files containing the exception.  */
  26
  27 #include <array_length.h>
  28 #include <errno.h>
  29 #include <limits.h>
  30 #include <math_ldbl_opt.h>
  31 #include <printf.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include <printf_buffer.h>
  36
  37 struct __printf_buffer_asprintf
  38 {
  39   /* base.write_base points either to a heap-allocated buffer, or to
  40      the direct array below.  */
  41   struct __printf_buffer base;
  42
  43   /* Initial allocation.  200 should be large enough to copy almost
  44      all asprintf usages with just a single (final, correctly sized)
  45      heap allocation.  */
  46   char direct[PRINTF_BUFFER_SIZE_ASPRINTF];
  47 };
  48
  49 void
  50 __printf_buffer_flush_asprintf (struct __printf_buffer_asprintf *buf)
  51 {
  52   size_t current_pos = buf->base.write_ptr - buf->base.write_base;
  53   if (current_pos >= INT_MAX)
  54     {
  55       /* The result is not representable.  No need to continue.  */
  56       __set_errno (EOVERFLOW);
  57       __printf_buffer_mark_failed (&buf->base);
  58       return;
  59     }
  60
  61   size_t current_size = buf->base.write_end - buf->base.write_base;
  62   /* Implement an exponentiation sizing policy.  Keep the size
  63      congruent 8 (mod 16), to account for the footer in glibc
  64      malloc.  */
  65   size_t new_size = ALIGN_UP (current_size + current_size / 2, 16) | 8;
  66   char *new_buffer;
  67   if (buf->base.write_base == buf->direct)
  68     {
  69       new_buffer = malloc (new_size);
  70       if (new_buffer == NULL)
  71         {
  72           __printf_buffer_mark_failed (&buf->base);
  73           return;
  74         }
  75       memcpy (new_buffer, buf->direct, current_pos);
  76     }
  77   else
  78     {
  79       new_buffer = realloc (buf->base.write_base, new_size);
  80       if (new_buffer == NULL)
  81         {
  82           __printf_buffer_mark_failed (&buf->base);
  83           return;
  84         }
  85     }
  86
  87   /* Set up the new write area.  */
  88   buf->base.write_base = new_buffer;
  89   buf->base.write_ptr = new_buffer + current_pos;
  90   buf->base.write_end = new_buffer + new_size;
  91 }
  92
  93
  94 int
  95 __vasprintf_internal (char **result_ptr, const char *format, va_list args,
  96                       unsigned int mode_flags)
  97 {
  98   struct __printf_buffer_asprintf buf;
  99   __printf_buffer_init (&buf.base, buf.direct, array_length (buf.direct),
 100                         __printf_buffer_mode_asprintf);
 101
 102   __printf_buffer (&buf.base, format, args, mode_flags);
 103   int done = __printf_buffer_done (&buf.base);
 104   if (done < 0)
 105     {
 106       if (buf.base.write_base != buf.direct)
 107         free (buf.base.write_base);
 108       return done;
 109     }
 110
 111   /* Transfer to the final buffer.  */
 112   char *result;
 113   size_t size = buf.base.write_ptr - buf.base.write_base;
 114   if (buf.base.write_base == buf.direct)
 115     {
 116       result = malloc (size + 1);
 117       if (result == NULL)
 118         return -1;
 119       memcpy (result, buf.direct, size);
 120     }
 121   else
 122     {
 123       result = realloc (buf.base.write_base, size + 1);
 124       if (result == NULL)
 125         {
 126           free (buf.base.write_base);
 127           return -1;
 128         }
 129     }
 130
 131   /* Add NUL termination.  */
 132   result[size] = '\0';
 133   *result_ptr = result;
 134
 135   return done;
 136 }
 137
 138 int
 139 __vasprintf (char **result_ptr, const char *format, va_list args)
 140 {
 141   return __vasprintf_internal (result_ptr, format, args, 0);
 142 }
 143 ldbl_weak_alias (__vasprintf, vasprintf)