libio/stdio/vsnprintf.c

   1 /* Copyright (C) 1994, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU IO Library.
   3
   4    This library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License as
   6    published by the Free Software Foundation; either version 2, or (at
   7    your option) any later version.
   8
   9    This library is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this library; see the file COPYING.  If not, write to
  16    the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  17    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
  21    not cause the resulting executable to be covered by the GNU General
  22    Public License.  This exception does not however invalidate any
  23    other reasons why the executable file might be covered by the GNU
  24    General Public License.  */
  25
  26 #include "libioP.h"
  27 #include "strfile.h"
  28
  29
  30 typedef struct
  31 {
  32   _IO_strfile f;
  33   /* This is used for the characters which do not fit in the buffer
  34      provided by the user.  */
  35   char overflow_buf[64];
  36 } _IO_strnfile;
  37
  38
  39 static int _IO_strn_overflow __P ((_IO_FILE *fp, int c));
  40
  41 static int
  42 _IO_strn_overflow (fp, c)
  43      _IO_FILE *fp;
  44      int c;
  45 {
  46   /* When we come to here this means the user supplied buffer is
  47      filled.  But since we must return the number of characters which
  48      would have been written in total we must provide a buffer for
  49      further use.  We can do this by writing on and on in the overflow
  50      buffer in the _IO_strnfile structure.  */
  51   _IO_strnfile *snf = (_IO_strnfile *) fp;
  52
  53   if (fp->_IO_buf_base != snf->overflow_buf)
  54     {
  55       /* Terminate the string.  We know that there is room for at
  56          least one more character since we initialized the stream with
  57          a size to make this possible.  */
  58       *fp->_IO_write_ptr = '\0';
  59
  60       _IO_setb (fp, snf->overflow_buf,
  61                 snf->overflow_buf + sizeof (snf->overflow_buf), 0);
  62
  63       fp->_IO_write_base = snf->overflow_buf;
  64       fp->_IO_read_base = snf->overflow_buf;
  65       fp->_IO_read_ptr = snf->overflow_buf;
  66       fp->_IO_read_end = snf->overflow_buf + sizeof (snf->overflow_buf);
  67     }
  68
  69   fp->_IO_write_ptr = snf->overflow_buf;
  70   fp->_IO_write_end = snf->overflow_buf;
  71
  72   /* Since we are not really interested in storing the characters
  73      which do not fit in the buffer we simply ignore it.  */
  74   return c;
  75 }
  76
  77
  78 static struct _IO_jump_t _IO_strn_jumps =
  79 {
  80   JUMP_INIT_DUMMY,
  81   JUMP_INIT(finish, _IO_str_finish),
  82   JUMP_INIT(overflow, _IO_strn_overflow),
  83   JUMP_INIT(underflow, _IO_str_underflow),
  84   JUMP_INIT(uflow, _IO_default_uflow),
  85   JUMP_INIT(pbackfail, _IO_str_pbackfail),
  86   JUMP_INIT(xsputn, _IO_default_xsputn),
  87   JUMP_INIT(xsgetn, _IO_default_xsgetn),
  88   JUMP_INIT(seekoff, _IO_str_seekoff),
  89   JUMP_INIT(seekpos, _IO_default_seekpos),
  90   JUMP_INIT(setbuf, _IO_default_setbuf),
  91   JUMP_INIT(sync, _IO_default_sync),
  92   JUMP_INIT(doallocate, _IO_default_doallocate),
  93   JUMP_INIT(read, _IO_default_read),
  94   JUMP_INIT(write, _IO_default_write),
  95   JUMP_INIT(seek, _IO_default_seek),
  96   JUMP_INIT(close, _IO_default_close),
  97   JUMP_INIT(stat, _IO_default_stat)
  98 };
  99
 100
 101 int
 102 _IO_vsnprintf (string, maxlen, format, args)
 103      char *string;
 104      _IO_size_t maxlen;
 105      const char *format;
 106      _IO_va_list args;
 107 {
 108   _IO_strnfile sf;
 109   int ret;
 110 #ifdef _IO_MTSAFE_IO
 111   _IO_lock_t lock;
 112   sf.f._sbf._f._lock = &lock;
 113 #endif
 114
 115   /* We need to handle the special case where MAXLEN is 0.  Use the
 116      overflow buffer right from the start.  */
 117   if (maxlen == 0)
 118     {
 119       string = sf.overflow_buf;
 120       maxlen = sizeof (sf.overflow_buf);
 121     }
 122
 123   _IO_init ((_IO_FILE *) &sf, 0);
 124   _IO_JUMPS ((_IO_FILE *) &sf) = &_IO_strn_jumps;
 125   _IO_str_init_static ((_IO_FILE *) &sf, string, maxlen - 1, string);
 126   ret = _IO_vfprintf ((_IO_FILE *) &sf, format, args);
 127
 128   if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
 129     *sf.f._sbf._f._IO_write_ptr = '\0';
 130   return ret;
 131 }
 132
 133 #ifdef weak_alias
 134 weak_alias (_IO_vsnprintf, __vsnprintf)
 135 weak_alias (_IO_vsnprintf, vsnprintf)
 136 #endif