libio/vsnprintf.c

   1 /*
   2 Copyright (C) 1994, 1997 Free Software Foundation, Inc.
   3
   4 This file is part of the GNU IO Library.  This library is free
   5 software; you can redistribute it and/or modify it under the
   6 terms of the GNU General Public License as published by the
   7 Free Software Foundation; either version 2, or (at your option)
   8 any later version.
   9
  10 This library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this library; see the file COPYING.  If not, write to the Free
  17 Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18
  19 As a special exception, if you link this library with files
  20 compiled with a GNU compiler to produce an executable, this does not cause
  21 the resulting executable to be covered by the GNU General Public License.
  22 This exception does not however invalidate any other reasons why
  23 the executable file might be covered by the GNU General Public License. */
  24
  25 #include "libioP.h"
  26 #include "strfile.h"
  27
  28
  29 typedef struct
  30 {
  31   _IO_strfile f;
  32   /* This is used for the characters which do not fit in the buffer
  33      provided by the user.  */
  34   char overflow_buf[64];
  35 } _IO_strnfile;
  36
  37
  38 static int
  39 _IO_strn_overflow (_IO_FILE* fp, int c)
  40 {
  41   /* When we come to here this means the user supplied buffer is
  42      filled.  But since we must return the number of characters which
  43      would have been written in total we must provide a buffer for
  44      further use.  We can do this by writing on and on in the overflow
  45      buffer in the _IO_strnfile structure.  */
  46   _IO_strnfile *snf = (_IO_strnfile *) fp;
  47
  48   if (fp->_IO_buf_base != snf->overflow_buf)
  49     {
  50       /* Terminate the string.  We know that there is room for at
  51          least one more character since we initialized the stream with
  52          a size to make this possible.  */
  53       *fp->_IO_write_ptr = '\0';
  54
  55       _IO_setb (fp, snf->overflow_buf,
  56                 snf->overflow_buf + sizeof (snf->overflow_buf), 0);
  57
  58       fp->_IO_write_base = snf->overflow_buf;
  59       fp->_IO_read_base = snf->overflow_buf;
  60       fp->_IO_read_ptr = snf->overflow_buf;
  61       fp->_IO_read_end = snf->overflow_buf + sizeof (snf->overflow_buf);
  62     }
  63
  64   fp->_IO_write_ptr = snf->overflow_buf;
  65   fp->_IO_write_end = snf->overflow_buf;
  66
  67   /* Since we are not really interested in storing the characters
  68      which do not fit in the buffer we simply ignore it.  */
  69   return c;
  70 }
  71
  72
  73 static struct _IO_jump_t _IO_strn_jumps = {
  74   JUMP_INIT_DUMMY,
  75   JUMP_INIT(finish, _IO_str_finish),
  76   JUMP_INIT(overflow, _IO_strn_overflow),
  77   JUMP_INIT(underflow, _IO_str_underflow),
  78   JUMP_INIT(uflow, _IO_default_uflow),
  79   JUMP_INIT(pbackfail, _IO_str_pbackfail),
  80   JUMP_INIT(xsputn, _IO_default_xsputn),
  81   JUMP_INIT(xsgetn, _IO_default_xsgetn),
  82   JUMP_INIT(seekoff, _IO_str_seekoff),
  83   JUMP_INIT(seekpos, _IO_default_seekpos),
  84   JUMP_INIT(setbuf, _IO_default_setbuf),
  85   JUMP_INIT(sync, _IO_default_sync),
  86   JUMP_INIT(doallocate, _IO_default_doallocate),
  87   JUMP_INIT(read, _IO_default_read),
  88   JUMP_INIT(write, _IO_default_write),
  89   JUMP_INIT(seek, _IO_default_seek),
  90   JUMP_INIT(close, _IO_default_close),
  91   JUMP_INIT(stat, _IO_default_stat)
  92 };
  93
  94
  95 int
  96 _IO_vsnprintf (string, maxlen, format, args)
  97      char *string;
  98      _IO_size_t maxlen;
  99      const char *format;
 100      _IO_va_list args;
 101 {
 102   _IO_strnfile sf;
 103   int ret;
 104 #ifdef _IO_MTSAFE_IO
 105   _IO_lock_t lock;
 106   sf.f._sbf._f._lock = &lock;
 107 #endif
 108
 109   /* We need to handle the special case where MAXLEN is 0.  Use the
 110      overflow buffer right from the start.  */
 111   if (maxlen == 0)
 112     {
 113       string = sf.overflow_buf;
 114       maxlen = sizeof (sf.overflow_buf);
 115     }
 116
 117   _IO_init ((_IO_FILE *) &sf, 0);
 118   _IO_JUMPS ((_IO_FILE *) &sf) = &_IO_strn_jumps;
 119   _IO_str_init_static ((_IO_FILE *) &sf, string, maxlen - 1, string);
 120   ret = _IO_vfprintf ((_IO_FILE *) &sf, format, args);
 121
 122   if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
 123     *sf.f._sbf._f._IO_write_ptr = '\0';
 124   return ret;
 125 }
 126 weak_alias (_IO_vsnprintf, __vsnprintf)
 127 weak_alias (_IO_vsnprintf, vsnprintf)