[PATCH 2/4] os/xprintf: add Xvscnprintf and Xscnprintf
Daniel Kurtz
djkurtz at chromium.org
Wed Apr 18 02:51:51 PDT 2012
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 at chromium.org>
---
include/Xprintf.h | 12 ++++++++++++
os/xprintf.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+), 0 deletions(-)
diff --git a/include/Xprintf.h b/include/Xprintf.h
index 414fd46..9e8cdc5 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 17fea2e..80caa57 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)
--
1.7.7.3
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