From 5c2e2a164d615ab06be28a663734e782614b5cc7 Mon Sep 17 00:00:00 2001 From: Daniel Kurtz Date: Wed, 18 Apr 2012 09:51:51 +0000 Subject: [PATCH] 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 Reviewed-by: Peter Hutterer Signed-off-by: Peter Hutterer --- include/Xprintf.h | 12 ++++++++++++ os/xprintf.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+) diff --git a/include/Xprintf.h b/include/Xprintf.h index 414fd46fb..9e8cdc5dc 100644 --- a/include/Xprintf.h +++ b/include/Xprintf.h @@ -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 */ diff --git a/os/xprintf.c b/os/xprintf.c index 17fea2ec7..80caa5790 100644 --- a/os/xprintf.c +++ b/os/xprintf.c @@ -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)