1 files changed, 109 insertions, 0 deletions
diff --git a/libntp/timetoa.c b/libntp/timetoa.c
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+++ b/libntp/timetoa.c
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+/*
+ * timetoa.c -- time_t related string formatting
+ *
+ * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project.
+ * The contents of 'html/copyright.html' apply.
+ *
+ * Printing a 'time_t' has a lot of portability pitfalls, due to it's
+ * opaque base type. The only requirement imposed by the standard is
+ * that it must be a numeric type. For all practical purposes it's a
+ * signed int, and 32 bits are common.
+ *
+ * Since the UN*X time epoch will cause a signed integer overflow for
+ * 32-bit signed int in the year 2038, implementations slowly move to
+ * 64bit base types for time_t, even in 32-bit environments.
+ *
+ * As the printf() family has no standardised type specifier for time_t,
+ * guessing the right output format specifier is a bit troublesome and
+ * best done with the help of the preprocessor and "config.h".
+ */
+
+#include "config.h"
+
+#include <math.h>
+#include <stdio.h>
+
+#include "timetoa.h"
+#include "ntp_assert.h"
+#include "lib_strbuf.h"
+
+/*
+ * Formatting to string needs at max 40 bytes (even with 64 bit time_t),
+ * so we check LIB_BUFLENGTH is big enough for our purpose.
+ */
+#if LIB_BUFLENGTH < 40
+# include "GRONK: LIB_BUFLENGTH is not sufficient"
+#endif
+
+/*
+ * general fractional timestamp formatting
+ *
+ * Many pieces of ntpd require a machine with two's complement
+ * representation of signed integers, so we don't go through the whole
+ * rigamarole of creating fully portable code here. But we have to stay
+ * away from signed integer overflow, as this might cause trouble even
+ * with two's complement representation.
+ */
+const char *
+format_time_fraction(
+	time_t	secs,
+	long	frac,
+	int	prec
+	)
+{
+	char *		cp;
+	u_int		prec_u;
+	u_time		secs_u;
+	u_int		u;
+	long		fraclimit;
+	int		notneg;	/* flag for non-negative value	*/
+	const char *	fmt;
+	ldiv_t		qr;
+
+	DEBUG_REQUIRE(prec != 0);
+
+	LIB_GETBUF(cp);
+	secs_u = (u_time)secs;
+	fmt = "-%" UTIME_FORMAT ".%0*ld";
+	
+	/* check if we need signed or unsigned mode */
+	notneg = (prec < 0);
+	prec_u = abs(prec);
+	/* fraclimit = (long)pow(10, prec_u); */
+	for (fraclimit = 10, u = 1; u < prec_u; u++) {
+		DEBUG_INSIST(fraclimit < fraclimit * 10);
+		fraclimit *= 10;
+	}
+
+	/*
+	 * Since conversion to string uses lots of divisions anyway,
+	 * there's no big extra penalty for normalisation. We do it for
+	 * consistency.
+	 */
+	if (frac < 0 || frac >= fraclimit) {
+		qr = ldiv(frac, fraclimit);
+		if (qr.rem < 0) {
+			qr.quot--;
+			qr.rem += fraclimit;
+		}
+		secs_u += (time_t)qr.quot;
+		frac = qr.rem;
+	}
+
+	/* Get the absolute value of the split representation time. */
+	notneg = notneg || ((time_t)secs_u >= 0);
+	if (notneg) {
+		fmt++;		/* skip '-' */
+	} else {
+		secs_u = ~secs_u;
+		if (0 == frac)
+			secs_u++;
+		else
+			frac = fraclimit - frac;
+	}
+
+	/* finally format the data and return the result */
+	snprintf(cp, LIB_BUFLENGTH, fmt, secs_u, prec_u, frac);
+	
+	return cp;
+}