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os/xprintf: add Xvscnprintf and Xscnprintf 

Normal snprintf() usually returns the number of bytes that would have been
written into a buffer had the buffer been long enough.

The scnprintf() variants return the actual number of bytes written,
excluding the trailing '\0'.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
This commit is contained in:
Daniel Kurtz 2012-04-18 09:51:51 +00:00 committed by Peter Hutterer
parent c30862879d
commit 5c2e2a164d
2 changed files with 56 additions and 0 deletions
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12
include/Xprintf.h
View File

@ -66,4 +66,16 @@ _X_ATTRIBUTE_PRINTF(2, 0);
#define vasprintf Xvasprintf
#endif
/*
* These functions provide a portable implementation of the linux kernel
* scnprintf & vscnprintf routines that return the number of bytes actually
* copied during a snprintf, (excluding the final '\0').
*/
extern _X_EXPORT int
Xscnprintf(char *s, int n, const char * _X_RESTRICT_KYWD fmt, ...)
_X_ATTRIBUTE_PRINTF(3,4);
extern _X_EXPORT int
Xvscnprintf(char *s, int n, const char * _X_RESTRICT_KYWD fmt, va_list va)
_X_ATTRIBUTE_PRINTF(3,0);
#endif /* XPRINTF_H */

44
os/xprintf.c
View File

@ -186,6 +186,50 @@ XNFasprintf(char **ret, const char *_X_RESTRICT_KYWD format, ...)
return size;
}
/**
* Varargs snprintf that returns the actual number of bytes (excluding final
* '\0') that were copied into the buffer.
* This is opposed to the normal sprintf() usually returns the number of bytes
* that would have been written.
*
* @param s buffer to copy into
* @param n size of buffer s
* @param format printf style format string
* @param va variable argument list
* @return number of bytes actually copied, excluding final '\0'
*/
int
Xvscnprintf(char *s, int n, const char *format, va_list args)
{
int x;
if (n == 0)
return 0;
x = vsnprintf(s, n , format, args);
return (x >= n) ? (n - 1) : x;
}
/**
* snprintf that returns the actual number of bytes (excluding final '\0') that
* were copied into the buffer.
* This is opposed to the normal sprintf() usually returns the number of bytes
* that would have been written.
*
* @param s buffer to copy into
* @param n size of buffer s
* @param format printf style format string
* @param ... arguments for specified format
* @return number of bytes actually copied, excluding final '\0'
*/
int Xscnprintf(char *s, int n, const char *format, ...)
{
int x;
va_list ap;
va_start(ap, format);
x = Xvscnprintf(s, n, format, ap);
va_end(ap);
return x;
}
/* Old api, now deprecated, may be removed in the future */
char *
Xvprintf(const char *format, va_list va)