usr/src/cmd/sendmail/libsm/vsnprintf.c

   1 /*
   2  * Copyright (c) 2000-2001 Sendmail, Inc. and its suppliers.
   3  *      All rights reserved.
   4  * Copyright (c) 1990, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Chris Torek.
   9  *
  10  * By using this file, you agree to the terms and conditions set
  11  * forth in the LICENSE file which can be found at the top level of
  12  * the sendmail distribution.
  13  */
  14
  15 #pragma ident   "%Z%%M% %I%     %E% SMI"
  16
  17 #include <sm/gen.h>
  18 SM_RCSID("@(#)$Id: vsnprintf.c,v 1.21 2001/03/04 23:28:41 ca Exp $")
  19 #include <limits.h>
  20 #include <sm/io.h>
  21 #include "local.h"
  22
  23 /*
  24 **  SM_VSNPRINTF -- format data for "output" into a string
  25 **
  26 **      Assigned 'str' to a "fake" file pointer. This allows common
  27 **      o/p formatting function sm_vprintf() to be used.
  28 **
  29 **      Parameters:
  30 **              str -- location for output
  31 **              n -- maximum size for o/p
  32 **              fmt -- format directives
  33 **              ap -- data unit vectors for use by 'fmt'
  34 **
  35 **      Results:
  36 **              result from sm_io_vfprintf()
  37 **
  38 **      Side Effects:
  39 **              Limits the size ('n') to INT_MAX.
  40 */
  41
  42 int
  43 sm_vsnprintf(str, n, fmt, ap)
  44         char *str;
  45         size_t n;
  46         const char *fmt;
  47         SM_VA_LOCAL_DECL
  48 {
  49         int ret;
  50         char dummy;
  51         SM_FILE_T fake;
  52
  53         /* While snprintf(3) specifies size_t stdio uses an int internally */
  54         if (n > INT_MAX)
  55                 n = INT_MAX;
  56
  57         /* Stdio internals do not deal correctly with zero length buffer */
  58         if (n == 0)
  59         {
  60                 str = &dummy;
  61                 n = 1;
  62         }
  63         fake.sm_magic = SmFileMagic;
  64         fake.f_timeout = SM_TIME_FOREVER;
  65         fake.f_timeoutstate = SM_TIME_BLOCK;
  66         fake.f_file = -1;
  67         fake.f_flags = SMWR | SMSTR;
  68         fake.f_bf.smb_base = fake.f_p = (unsigned char *)str;
  69         fake.f_bf.smb_size = fake.f_w = n - 1;
  70         fake.f_close = NULL;
  71         fake.f_open = NULL;
  72         fake.f_read = NULL;
  73         fake.f_write = NULL;
  74         fake.f_seek = NULL;
  75         fake.f_setinfo = fake.f_getinfo = NULL;
  76         fake.f_type = "sm_vsnprintf:fake";
  77         ret = sm_io_vfprintf(&fake, SM_TIME_FOREVER, fmt, ap);
  78         *fake.f_p = 0;
  79         return ret;
  80 }