libio/vsnprintf.c

   1 /* Copyright (C) 1994-2024 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    As a special exception, if you link the code in this file with
  19    files compiled with a GNU compiler to produce an executable,
  20    that does not cause the resulting executable to be covered by
  21    the GNU Lesser General Public License.  This exception does not
  22    however invalidate any other reasons why the executable file
  23    might be covered by the GNU Lesser General Public License.
  24    This exception applies to code released by its copyright holders
  25    in files containing the exception.  */
  26
  27 #include "libioP.h"
  28
  29 #include <array_length.h>
  30 #include <printf.h>
  31 #include <printf_buffer.h>
  32
  33 void
  34 __printf_buffer_flush_snprintf (struct __printf_buffer_snprintf *buf)
  35 {
  36   /* Record the bytes written so far, before switching buffers.  */
  37   buf->base.written += buf->base.write_ptr - buf->base.write_base;
  38
  39   if (buf->base.write_base != buf->discard)
  40     {
  41       /* We just finished writing the caller-supplied buffer.  Force
  42          NUL termination if the string length is not zero.  */
  43       if (buf->base.write_base != buf->base.write_end)
  44         buf->base.write_end[-1] = '\0';
  45
  46
  47       /* Switch to the discard buffer.  */
  48       buf->base.write_base = buf->discard;
  49       buf->base.write_ptr = buf->discard;
  50       buf->base.write_end = array_end (buf->discard);
  51     }
  52
  53   buf->base.write_base = buf->discard;
  54   buf->base.write_ptr = buf->discard;
  55 }
  56
  57 void
  58 __printf_buffer_snprintf_init (struct __printf_buffer_snprintf *buf,
  59                                char *buffer, size_t length)
  60 {
  61   __printf_buffer_init (&buf->base, buffer, length,
  62                         __printf_buffer_mode_snprintf);
  63   if (length > 0)
  64     /* Historic behavior for trivially overlapping buffers (checked by
  65        the test suite).  */
  66     *buffer = '\0';
  67 }
  68
  69 int
  70 __printf_buffer_snprintf_done (struct __printf_buffer_snprintf *buf)
  71 {
  72   /* NB: Do not check for buf->base.fail here.  Write the null
  73      terminator even in case of errors. */
  74
  75   if (buf->base.write_ptr < buf->base.write_end)
  76     *buf->base.write_ptr = '\0';
  77   else if (buf->base.write_ptr > buf->base.write_base)
  78     /* If write_ptr == write_base, nothing has been written.  No null
  79        termination is needed because of the early truncation in
  80        __printf_buffer_snprintf_init (the historic behavior).
  81
  82        We might also be at the start of the discard buffer, but in
  83        this case __printf_buffer_flush_snprintf has already written
  84        the NUL terminator.  */
  85     buf->base.write_ptr[-1] = '\0';
  86
  87   return __printf_buffer_done (&buf->base);
  88 }
  89
  90 int
  91 __vsnprintf_internal (char *string, size_t maxlen, const char *format,
  92                       va_list args, unsigned int mode_flags)
  93 {
  94   struct __printf_buffer_snprintf buf;
  95   __printf_buffer_snprintf_init (&buf, string, maxlen);
  96   __printf_buffer (&buf.base, format, args, mode_flags);
  97   return __printf_buffer_snprintf_done (&buf);
  98 }
  99
 100 int
 101 ___vsnprintf (char *string, size_t maxlen, const char *format, va_list args)
 102 {
 103   return __vsnprintf_internal (string, maxlen, format, args, 0);
 104 }
 105 ldbl_weak_alias (___vsnprintf, __vsnprintf)
 106 ldbl_weak_alias (___vsnprintf, vsnprintf)