libio/memstream.c

   1 /* Copyright (C) 1995-2024 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 #include "libioP.h"
  19 #include "strfile.h"
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22
  23
  24 struct _IO_FILE_memstream
  25 {
  26   _IO_strfile _sf;
  27   char **bufloc;
  28   size_t *sizeloc;
  29 };
  30
  31
  32 /* Open a stream that writes into a malloc'd buffer that is expanded as
  33    necessary.  *BUFLOC and *SIZELOC are updated with the buffer's location
  34    and the number of characters written on fflush or fclose.  */
  35 FILE *
  36 __open_memstream (char **bufloc, size_t *sizeloc)
  37 {
  38   struct locked_FILE
  39   {
  40     struct _IO_FILE_memstream fp;
  41 #ifdef _IO_MTSAFE_IO
  42     _IO_lock_t lock;
  43 #endif
  44     struct _IO_wide_data wd;
  45   } *new_f;
  46   char *buf;
  47
  48   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
  49   if (new_f == NULL)
  50     return NULL;
  51 #ifdef _IO_MTSAFE_IO
  52   new_f->fp._sf._sbf._f._lock = &new_f->lock;
  53 #endif
  54
  55   buf = calloc (1, BUFSIZ);
  56   if (buf == NULL)
  57     {
  58       free (new_f);
  59       return NULL;
  60     }
  61   _IO_init_internal (&new_f->fp._sf._sbf._f, 0);
  62   _IO_JUMPS_FILE_plus (&new_f->fp._sf._sbf) = &_IO_mem_jumps;
  63   _IO_str_init_static_internal (&new_f->fp._sf, buf, BUFSIZ, buf);
  64   new_f->fp._sf._sbf._f._flags &= ~_IO_USER_BUF;
  65   new_f->fp._sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc;
  66   new_f->fp._sf._s._free_buffer_unused = (_IO_free_type) free;
  67
  68   new_f->fp.bufloc = bufloc;
  69   new_f->fp.sizeloc = sizeloc;
  70
  71   /* Disable single thread optimization.  BZ 21735.  */
  72   new_f->fp._sf._sbf._f._flags2 |= _IO_FLAGS2_NEED_LOCK;
  73
  74   return (FILE *) &new_f->fp._sf._sbf;
  75 }
  76 libc_hidden_def (__open_memstream)
  77 weak_alias (__open_memstream, open_memstream)
  78
  79
  80 int
  81 _IO_mem_sync (FILE *fp)
  82 {
  83   struct _IO_FILE_memstream *mp = (struct _IO_FILE_memstream *) fp;
  84
  85   if (fp->_IO_write_ptr == fp->_IO_write_end)
  86     {
  87       _IO_str_overflow (fp, '\0');
  88       --fp->_IO_write_ptr;
  89     }
  90
  91   *mp->bufloc = fp->_IO_write_base;
  92   *mp->sizeloc = fp->_IO_write_ptr - fp->_IO_write_base;
  93
  94   return 0;
  95 }
  96
  97
  98 void
  99 _IO_mem_finish (FILE *fp, int dummy)
 100 {
 101   struct _IO_FILE_memstream *mp = (struct _IO_FILE_memstream *) fp;
 102
 103   *mp->bufloc = (char *) realloc (fp->_IO_write_base,
 104                                   fp->_IO_write_ptr - fp->_IO_write_base + 1);
 105   if (*mp->bufloc != NULL)
 106     {
 107       (*mp->bufloc)[fp->_IO_write_ptr - fp->_IO_write_base] = '\0';
 108       *mp->sizeloc = fp->_IO_write_ptr - fp->_IO_write_base;
 109
 110       fp->_IO_buf_base = NULL;
 111     }
 112
 113   _IO_str_finish (fp, 0);
 114 }