Back ZipEntry.DateTime with a real DateTime field instead of DosTime

Otherwise we lose the additional accuracy we gain from Unix or NT timestamps.
Changing DateTime externally also changes DosTime. DosTime is only mapped to DateTime once on load, if there is no Unix or NT timestamp.

Author: bastianeicher

ICSharpCode.SharpZipLib/Zip/ZipEntry.cs

@@ -257,6 +257,7 @@ public ZipEntry(ZipEntry entry)
 			compressedSize = entry.compressedSize;
 			crc = entry.crc;
 			dosTime = entry.dosTime;
+			dateTime = entry.dateTime;
 			method = entry.method;
 			comment = entry.comment;
 			versionToExtract = entry.versionToExtract;
@@ -706,16 +707,7 @@ public long DosTime
 		/// </remarks>
 		public DateTime DateTime
 		{
-			get
-			{
-				uint sec = Math.Min(59, 2 * (dosTime & 0x1f));
-				uint min = Math.Min(59, (dosTime >> 5) & 0x3f);
-				uint hrs = Math.Min(23, (dosTime >> 11) & 0x1f);
-				uint mon = Math.Max(1, Math.Min(12, ((dosTime >> 21) & 0xf)));
-				uint year = ((dosTime >> 25) & 0x7f) + 1980;
-				int day = Math.Max(1, Math.Min(DateTime.DaysInMonth((int)year, (int)mon), (int)((dosTime >> 16) & 0x1f)));
-				return new System.DateTime((int)year, (int)mon, day, (int)hrs, (int)min, (int)sec);
-			}
+			get { return dateTime; }
 
 			set
 			{
@@ -1058,7 +1050,7 @@ internal void ProcessExtraData(bool localHeader)
 							long lastAccess = extraData.ReadLong();
 							long createTime = extraData.ReadLong();
 
-							DateTime = System.DateTime.FromFileTimeUtc(lastModification);
+							dateTime = System.DateTime.FromFileTimeUtc(lastModification);
 						}
 						break;
 					} else {
@@ -1075,9 +1067,17 @@ internal void ProcessExtraData(bool localHeader)
 				if (((flags & 1) != 0) && (length >= 5)) {
 					int iTime = extraData.ReadInt();
 
-					DateTime = (new System.DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc ) +
-						new TimeSpan(0, 0, 0, iTime, 0));
+					dateTime = (new System.DateTime ( 1970, 1, 1, 0, 0, 0, DateTimeKind.Utc ) +
+						new TimeSpan ( 0, 0, 0, iTime, 0 ));
 				}
+			} else {
+				uint sec = Math.Min(59, 2 * (dosTime & 0x1f));
+				uint min = Math.Min(59, (dosTime >> 5) & 0x3f);
+				uint hrs = Math.Min(23, (dosTime >> 11) & 0x1f);
+				uint mon = Math.Max(1, Math.Min(12, ((dosTime >> 21) & 0xf)));
+				uint year = ((dosTime >> 25) & 0x7f) + 1980;
+				int day = Math.Max(1, Math.Min(DateTime.DaysInMonth((int)year, (int)mon), (int)((dosTime >> 16) & 0x1f)));
+				dateTime = new DateTime((int)year, (int)mon, day, (int)hrs, (int)min, (int)sec, DateTimeKind.Utc);
 			}
 			if (method == CompressionMethod.WinZipAES) {
 				ProcessAESExtraData(extraData);
@@ -1281,6 +1281,7 @@ public static string CleanName(string name)
 		ushort versionToExtract;                // Version required to extract (library handles <= 2.0)
 		uint crc;
 		uint dosTime;
+		DateTime dateTime;
 
 		CompressionMethod method = CompressionMethod.Deflated;
 		byte[] extra;