1 files changed, 90 insertions, 24 deletions

diff --git a/src/expire.c b/src/expire.c
index 23ce6ae..2207d3c 100644
--- a/src/expire.c
+++ b/src/expire.c
@@ -20,9 +20,11 @@
 /******************************************************************************/
 /******************************************************************************/
 
+#include <stdbool.h>
 #include <time.h>
 #include <string.h>
 #include <stdio.h>
+#include <limits.h>
 
 #include "expire.h"
 
@@ -31,52 +33,116 @@ static const int MIN = 60;
 static const int HOUR = 60*60;
 static const int DAY = 24*60*60;
 static const int WEEK = 7*24*60*60;
-static const int YEAR = 365*24*60*60 + 24*60*60/4;
+static const int YEAR = 365*24*60*60 + 24*60*60/4; /* average includes leap */
+static const time_t TMIN = (time_t)1 << ((CHAR_BIT * sizeof(time_t)) - 1);
+static const time_t TMAX = ~TMIN;
 
-/* see expire.h */
-time_t txt2exp(const char *txt)
+/** add positives x and y with saturation */
+static time_t pt_add(time_t x, time_t y)
 {
-	time_t r, x;
+	time_t r = x + y;
+	return r < 0 ? TMAX : r;
+}
 
-	/* infinite time */
-	if (!strcmp(txt, "always") || !strcmp(txt, "forever") || !strcmp(txt, "*"))
-		return 0;
+/** multiply positive x by m with saturation */
+static time_t pt_mul(time_t x, int m)
+{
+	time_t r;
+
+	if (m <= 1)
+		r = 0;
+	else {
+		r = pt_mul(x, m >> 1) << 1;
+		if (r < 0)
+			r = TMAX;
+	}
+	return (m & 1) ? pt_add(r, x) : r;
+}
+
+/** multiply positive x by m and then add y with saturation */
+static time_t pt_muladd(time_t x, int m, time_t y)
+{
+	return pt_add(pt_mul(x, m), y);
+}
+
+/** multiply positive x by 10 and then add d with saturation */
+static time_t pt_tm10a(time_t x, int d)
+{
+	return pt_muladd(x, 10, (time_t)d);
+}
+
+/** translate the string 'txt' to its time representation */
+static bool parse_time_spec(const char *txt, time_t *time_out)
+{
+	time_t r, x;
 
 	/* parse */
-	r = time(NULL);
+	r = 0;
 	while(*txt) {
 		x = 0;
 		while('0' <= *txt && *txt <= '9')
-			x = (x << 3) + (x << 1) + (time_t)(*txt++ - '0');
+			x = pt_tm10a(x, *txt++ - '0');
 		switch(*txt) {
-		case 'y': r += x * YEAR; txt++; break;
-		case 'w': r += x * WEEK; txt++; break;
-		case 'd': r += x * DAY; txt++; break;
-		case 'h': r += x * HOUR; txt++; break;
-		case 'm': r += x * MIN; txt++; break;
+		case 'y': r = pt_muladd(x, YEAR, r); txt++; break;
+		case 'w': r = pt_muladd(x, WEEK, r); txt++; break;
+		case 'd': r = pt_muladd(x, DAY, r); txt++; break;
+		case 'h': r = pt_muladd(x, HOUR, r); txt++; break;
+		case 'm': r = pt_muladd(x, MIN, r); txt++; break;
 		case 's': txt++; /*@fallthrough@*/
-		case 0: r += x * SEC; break;
-		default: return -1;
+		case 0: r = pt_muladd(x, SEC, r); break;
+		default: return false;
 		}
 	}
-	return r;
+	*time_out = r;
+	return true;
+}
+
+
+/* see expire.h */
+bool txt2exp(const char *txt, time_t *time_out)
+{
+	bool nocache;
+	time_t r;
+
+	/* no cache */
+	nocache = txt[0] == '-';
+	txt += nocache;
+
+	/* infinite time */
+	if (!txt[0] || !strcmp(txt, "always") || !strcmp(txt, "forever") || !strcmp(txt, "*")) {
+		r = 0;
+	} else {
+		/* parse */
+		if (!parse_time_spec(txt, &r))
+			return false;
+		/* relative time */
+		r = pt_add(r, time(NULL));
+	}
+
+	*time_out = nocache ? -(r + 1) : r;
+	return true;
 }
 
 /* see expire.h */
 size_t exp2txt(time_t expire, char *buffer, size_t buflen)
 {
 	char b[100];
-	size_t l;
-	int n;
+	size_t l, n;
 
-	if (!expire)
-		strncpy(b, "forever", sizeof b);
-	else {
+	n = 0;
+	if (expire < 0) {
+		b[n++] = '-';
+		b[n] = 0;
+		expire = -(expire + 1);
+	}
+	if (!expire) {
+		if (!n)
+			strncpy(b, "forever", sizeof b);
+	} else {
 		expire -= time(NULL);
-		n = 0;
 #define ADD(C,U) \
   if (expire >= U) { \
-    n += snprintf(&b[n], sizeof b - (size_t)n, "%lld" #C, (long long)(expire / U)); \
+    n += (size_t)snprintf(&b[n], sizeof b - (size_t)n, "%lld" #C, (long long)(expire / U)); \
     expire %= U; \
   }
 		ADD(y,YEAR)