sergiotarxz/nuttx
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

snprintf(): If size is zero, then snprintf() should return the size of the required buffer without writing anyting. From Sami Pelkonen

Browse Source
This commit is contained in:
Gregory Nutt 2014-05-30 08:53:43 -06:00
parent 6f3cb90c05
commit 59846a8fe9
1 changed files with 29 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
libc/stdio/lib_snprintf.c
View File

@ -1,7 +1,7 @@
/****************************************************************************
* libc/stdio/lib_snprintf.c
*
* Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
* Copyright (C) 2007-2009, 2011, 2014 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
@ -82,19 +82,41 @@
int snprintf(FAR char *buf, size_t size, const char *format, ...)
{
struct lib_memoutstream_s memoutstream;
union
{
struct lib_outstream_s nulloutstream;
struct lib_memoutstream_s memoutstream;
} u;
FAR struct lib_outstream_s *stream;
va_list ap;
int n;
int n;
/* Initialize a memory stream to write to the buffer */
/* "If the value of [size] is zero on a call to snprintf(), nothing shall
* be written, the number of bytes that would have been written had [size]
* been sufficiently large excluding the terminating null shall be returned,
* and [buf] may be a null pointer." -- opengroup.org
*/
lib_memoutstream((FAR struct lib_memoutstream_s *)&memoutstream, buf, size);
if (size > 0)
{
/* Initialize a memory stream to write to the buffer */
lib_memoutstream(&u.memoutstream, buf, size);
stream = &u.memoutstream.public;
}
else
{
/* Use a null stream to get the size of the buffer */
lib_nulloutstream(&u.nulloutstream);
stream = &u.nulloutstream;
}
/* Then let lib_vsprintf do the real work */
va_start(ap, format);
n = lib_vsprintf((FAR struct lib_outstream_s *)&memoutstream.public,
format, ap);
n = lib_vsprintf(stream, format, ap);
va_end(ap);
return n;
}