libio/vsnprintf.c

   1 /* Copyright (C) 1994,1997,1999-2003, 2004 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.
  18
  19    As a special exception, if you link the code in this file with
  20    files compiled with a GNU compiler to produce an executable,
  21    that does not cause the resulting executable to be covered by
  22    the GNU Lesser General Public License.  This exception does not
  23    however invalidate any other reasons why the executable file
  24    might be covered by the GNU Lesser General Public License.
  25    This exception applies to code released by its copyright holders
  26    in files containing the exception.  */
  27
  28 #include "libioP.h"
  29 #include "strfile.h"
  30
  31
  32 typedef struct
  33 {
  34   _IO_strfile f;
  35   /* This is used for the characters which do not fit in the buffer
  36      provided by the user.  */
  37   char overflow_buf[64];
  38 } _IO_strnfile;
  39
  40
  41 static int _IO_strn_overflow __P ((_IO_FILE *fp, int c));
  42
  43 static int
  44 _IO_strn_overflow (fp, c)
  45      _IO_FILE *fp;
  46      int c;
  47 {
  48   /* When we come to here this means the user supplied buffer is
  49      filled.  But since we must return the number of characters which
  50      would have been written in total we must provide a buffer for
  51      further use.  We can do this by writing on and on in the overflow
  52      buffer in the _IO_strnfile structure.  */
  53   _IO_strnfile *snf = (_IO_strnfile *) fp;
  54
  55   if (fp->_IO_buf_base != snf->overflow_buf)
  56     {
  57       /* Terminate the string.  We know that there is room for at
  58          least one more character since we initialized the stream with
  59          a size to make this possible.  */
  60       *fp->_IO_write_ptr = '\0';
  61
  62       INTUSE(_IO_setb) (fp, snf->overflow_buf,
  63                         snf->overflow_buf + sizeof (snf->overflow_buf), 0);
  64
  65       fp->_IO_write_base = snf->overflow_buf;
  66       fp->_IO_read_base = snf->overflow_buf;
  67       fp->_IO_read_ptr = snf->overflow_buf;
  68       fp->_IO_read_end = snf->overflow_buf + sizeof (snf->overflow_buf);
  69     }
  70
  71   fp->_IO_write_ptr = snf->overflow_buf;
  72   fp->_IO_write_end = snf->overflow_buf;
  73
  74   /* Since we are not really interested in storing the characters
  75      which do not fit in the buffer we simply ignore it.  */
  76   return c;
  77 }
  78
  79
  80 static const struct _IO_jump_t _IO_strn_jumps =
  81 {
  82   JUMP_INIT_DUMMY,
  83   JUMP_INIT(finish, _IO_str_finish),
  84   JUMP_INIT(overflow, _IO_strn_overflow),
  85   JUMP_INIT(underflow, INTUSE(_IO_str_underflow)),
  86   JUMP_INIT(uflow, INTUSE(_IO_default_uflow)),
  87   JUMP_INIT(pbackfail, INTUSE(_IO_str_pbackfail)),
  88   JUMP_INIT(xsputn, INTUSE(_IO_default_xsputn)),
  89   JUMP_INIT(xsgetn, INTUSE(_IO_default_xsgetn)),
  90   JUMP_INIT(seekoff, INTUSE(_IO_str_seekoff)),
  91   JUMP_INIT(seekpos, _IO_default_seekpos),
  92   JUMP_INIT(setbuf, _IO_default_setbuf),
  93   JUMP_INIT(sync, _IO_default_sync),
  94   JUMP_INIT(doallocate, INTUSE(_IO_default_doallocate)),
  95   JUMP_INIT(read, _IO_default_read),
  96   JUMP_INIT(write, _IO_default_write),
  97   JUMP_INIT(seek, _IO_default_seek),
  98   JUMP_INIT(close, _IO_default_close),
  99   JUMP_INIT(stat, _IO_default_stat),
 100   JUMP_INIT(showmanyc, _IO_default_showmanyc),
 101   JUMP_INIT(imbue, _IO_default_imbue)
 102 };
 103
 104
 105 int
 106 _IO_vsnprintf (string, maxlen, format, args)
 107      char *string;
 108      _IO_size_t maxlen;
 109      const char *format;
 110      _IO_va_list args;
 111 {
 112   _IO_strnfile sf;
 113   int ret;
 114 #ifdef _IO_MTSAFE_IO
 115   sf.f._sbf._f._lock = NULL;
 116 #endif
 117
 118   /* We need to handle the special case where MAXLEN is 0.  Use the
 119      overflow buffer right from the start.  */
 120   if (maxlen == 0)
 121     {
 122       string = sf.overflow_buf;
 123       maxlen = sizeof (sf.overflow_buf);
 124     }
 125
 126   _IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
 127   _IO_JUMPS ((struct _IO_FILE_plus *) &sf.f._sbf) = &_IO_strn_jumps;
 128   string[0] = '\0';
 129   _IO_str_init_static_internal (&sf.f, string, maxlen - 1, string);
 130   ret = INTUSE(_IO_vfprintf) ((_IO_FILE *) &sf.f._sbf, format, args);
 131
 132   if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
 133     *sf.f._sbf._f._IO_write_ptr = '\0';
 134   return ret;
 135 }
 136
 137 #ifdef weak_alias
 138 weak_alias (_IO_vsnprintf, __vsnprintf)
 139 weak_alias (_IO_vsnprintf, vsnprintf)
 140 #endif