Ensure datetime is always in range, add tests

src/util.rs

@@ -1,4 +1,4 @@
-use time::{Tm, empty_tm};
+use time::{self, Tm};
 
 pub fn msdos_datetime_to_tm(time: u16, date: u16) -> Tm
 {
@@ -12,15 +12,19 @@ pub fn msdos_datetime_to_tm(time: u16, date: u16) -> Tm
     // Month range: Dos [1..12], Tm [0..11]
     // Year zero: Dos 1980, Tm 1900
 
-    Tm {
+    let tm = Tm {
         tm_sec: seconds as i32,
         tm_min: minutes as i32,
         tm_hour: hours as i32,
         tm_mday: days as i32,
         tm_mon: months as i32 - 1,
         tm_year: years as i32 + 80,
-        ..empty_tm()
-    }
+        ..time::empty_tm()
+    };
+
+    // Re-parse the possibly incorrect timestamp to get a correct one.
+    // This every value will be in range
+    time::at_utc(tm.to_timespec())
 }
 
 pub fn tm_to_msdos_time(time: Tm) -> u16
@@ -32,3 +36,72 @@ pub fn tm_to_msdos_date(time: Tm) -> u16
 {
     (time.tm_mday | ((time.tm_mon + 1) << 5) | ((time.tm_year - 80) << 9)) as u16
 }
+
+#[cfg(test)]
+mod dos_tm_test {
+    use super::*;
+    use time::{self, Tm};
+
+    fn check_date(input: Tm, day: i32, month: i32, year: i32) {
+        assert_eq!(input.tm_mday, day);
+        assert_eq!(input.tm_mon + 1, month);
+        assert_eq!(input.tm_year + 1900, year);
+    }
+
+    fn check_time(input: Tm, hour: i32, minute: i32, second: i32) {
+        assert_eq!(input.tm_hour, hour);
+        assert_eq!(input.tm_min, minute);
+        assert_eq!(input.tm_sec, second);
+    }
+
+    #[test]
+    fn dos_zero() {
+        // The 0 date is actually not a correct msdos date, but we
+        // will parse it and adjust accordingly.
+        let tm = msdos_datetime_to_tm(0, 0);
+        check_date(tm, 30, 11, 1979);
+        check_time(tm, 0, 0, 0);
+
+        // This is the actual smallest date possible
+        let tm = msdos_datetime_to_tm(0, 0b100001);
+        check_date(tm, 1, 1, 1980);
+        check_time(tm, 0, 0, 0);
+    }
+
+    #[test]
+    fn dos_today() {
+        let tm = msdos_datetime_to_tm(0b01001_100000_10101, 0b0100011_0110_11110);
+        check_date(tm, 30, 6, 2015);
+        check_time(tm, 9, 32, 42);
+    }
+
+    #[test]
+    fn zero_dos() {
+        let tm = Tm {
+            tm_year: 80,
+            tm_mon: 0,
+            tm_mday: 1,
+            tm_hour: 0,
+            tm_min: 0,
+            tm_sec: 0,
+            ..time::empty_tm()
+        };
+        assert_eq!(tm_to_msdos_date(tm), 0b100001);
+        assert_eq!(tm_to_msdos_time(tm), 0);
+    }
+
+    #[test]
+    fn today_dos() {
+        let tm = Tm {
+            tm_year: 115,
+            tm_mon: 5,
+            tm_mday: 30,
+            tm_hour: 9,
+            tm_min: 32,
+            tm_sec: 42,
+            ..time::empty_tm()
+        };
+        assert_eq!(tm_to_msdos_date(tm), 0b0100011_0110_11110);
+        assert_eq!(tm_to_msdos_time(tm), 0b01001_100000_10101);
+    }
+}