libio/memstream.c

   1 /* Copyright (C) 1995-2021 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 static int _IO_mem_sync (FILE* fp) __THROW;
  33 static void _IO_mem_finish (FILE* fp, int) __THROW;
  34
  35
  36 static const struct _IO_jump_t _IO_mem_jumps libio_vtable =
  37 {
  38   JUMP_INIT_DUMMY,
  39   JUMP_INIT (finish, _IO_mem_finish),
  40   JUMP_INIT (overflow, _IO_str_overflow),
  41   JUMP_INIT (underflow, _IO_str_underflow),
  42   JUMP_INIT (uflow, _IO_default_uflow),
  43   JUMP_INIT (pbackfail, _IO_str_pbackfail),
  44   JUMP_INIT (xsputn, _IO_default_xsputn),
  45   JUMP_INIT (xsgetn, _IO_default_xsgetn),
  46   JUMP_INIT (seekoff, _IO_str_seekoff),
  47   JUMP_INIT (seekpos, _IO_default_seekpos),
  48   JUMP_INIT (setbuf, _IO_default_setbuf),
  49   JUMP_INIT (sync, _IO_mem_sync),
  50   JUMP_INIT (doallocate, _IO_default_doallocate),
  51   JUMP_INIT (read, _IO_default_read),
  52   JUMP_INIT (write, _IO_default_write),
  53   JUMP_INIT (seek, _IO_default_seek),
  54   JUMP_INIT (close, _IO_default_close),
  55   JUMP_INIT (stat, _IO_default_stat),
  56   JUMP_INIT(showmanyc, _IO_default_showmanyc),
  57   JUMP_INIT(imbue, _IO_default_imbue)
  58 };
  59
  60 /* Open a stream that writes into a malloc'd buffer that is expanded as
  61    necessary.  *BUFLOC and *SIZELOC are updated with the buffer's location
  62    and the number of characters written on fflush or fclose.  */
  63 FILE *
  64 __open_memstream (char **bufloc, size_t *sizeloc)
  65 {
  66   struct locked_FILE
  67   {
  68     struct _IO_FILE_memstream fp;
  69 #ifdef _IO_MTSAFE_IO
  70     _IO_lock_t lock;
  71 #endif
  72     struct _IO_wide_data wd;
  73   } *new_f;
  74   char *buf;
  75
  76   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
  77   if (new_f == NULL)
  78     return NULL;
  79 #ifdef _IO_MTSAFE_IO
  80   new_f->fp._sf._sbf._f._lock = &new_f->lock;
  81 #endif
  82
  83   buf = calloc (1, BUFSIZ);
  84   if (buf == NULL)
  85     {
  86       free (new_f);
  87       return NULL;
  88     }
  89   _IO_init_internal (&new_f->fp._sf._sbf._f, 0);
  90   _IO_JUMPS_FILE_plus (&new_f->fp._sf._sbf) = &_IO_mem_jumps;
  91   _IO_str_init_static_internal (&new_f->fp._sf, buf, BUFSIZ, buf);
  92   new_f->fp._sf._sbf._f._flags &= ~_IO_USER_BUF;
  93   new_f->fp._sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc;
  94   new_f->fp._sf._s._free_buffer_unused = (_IO_free_type) free;
  95
  96   new_f->fp.bufloc = bufloc;
  97   new_f->fp.sizeloc = sizeloc;
  98
  99   /* Disable single thread optimization.  BZ 21735.  */
 100   new_f->fp._sf._sbf._f._flags2 |= _IO_FLAGS2_NEED_LOCK;
 101
 102   return (FILE *) &new_f->fp._sf._sbf;
 103 }
 104 libc_hidden_def (__open_memstream)
 105 weak_alias (__open_memstream, open_memstream)
 106
 107
 108 static int
 109 _IO_mem_sync (FILE *fp)
 110 {
 111   struct _IO_FILE_memstream *mp = (struct _IO_FILE_memstream *) fp;
 112
 113   if (fp->_IO_write_ptr == fp->_IO_write_end)
 114     {
 115       _IO_str_overflow (fp, '\0');
 116       --fp->_IO_write_ptr;
 117     }
 118
 119   *mp->bufloc = fp->_IO_write_base;
 120   *mp->sizeloc = fp->_IO_write_ptr - fp->_IO_write_base;
 121
 122   return 0;
 123 }
 124
 125
 126 static void
 127 _IO_mem_finish (FILE *fp, int dummy)
 128 {
 129   struct _IO_FILE_memstream *mp = (struct _IO_FILE_memstream *) fp;
 130
 131   *mp->bufloc = (char *) realloc (fp->_IO_write_base,
 132                                   fp->_IO_write_ptr - fp->_IO_write_base + 1);
 133   if (*mp->bufloc != NULL)
 134     {
 135       (*mp->bufloc)[fp->_IO_write_ptr - fp->_IO_write_base] = '\0';
 136       *mp->sizeloc = fp->_IO_write_ptr - fp->_IO_write_base;
 137
 138       fp->_IO_buf_base = NULL;
 139     }
 140
 141   _IO_str_finish (fp, 0);
 142 }