Fix/add details about the ExtTime structure

docs/unrar.html

@@ -153,7 +153,7 @@ PackSize                4 bytes
 UnpSize                 4 bytes
 HostOS                  1 byte
 FileCRC                 4 bytes
-FileTime                4 bytes
+FileTime (mtime)        4 bytes (MS-DOS date/time format)
 UnpVer                  1 byte
 Method                  1 byte
 NameSize                2 bytes
@@ -171,39 +171,63 @@ Packed Data             (Total Packed Size) bytes
 <header>
 	<h6 id="ext-time-structure"><a href="#ext-time-structure">ExtTime Structure</a></h6>
 </header>
+	
+<p>This structure has 4 sections representing additional time data.</p>
+<p>The first 16 bits contain a set of flags, 4 bits for each section.</p>
 
+<p>Each flag contains:</p>
+<ul>
+	<li>Bit 0: Whether this section is present or not</li>
+	<li>Bit 1 and 2: The amount of bytes to be read as the remainder, between 0 and 3</li>
+	<li>Bit 4: Signals that the MS-DOS date/time should have its seconds increased by 1</li>
+	<ul>
+		<li>MS-DOS date/time format can only store even numbers of seconds. This bit counters this limitation.</li>
+	</ul>
+</ul>
+	
+<p>Each section contains:</p>
+	
+<ul>
+	<li>4 bytes containing an MS-DOS date/time (except for mtime, which is part of FILE_HEAD)</li>
+	<li>0 to 3 bytes containing fractions of seconds in 100ns increments</li>
+</ul>
+	
 <p>Follow the following pseudo-code to read in the ExtTime Structure.</p>
-<p><strong>TODO: Fill in details of what this structure represents.</strong></p>
 
 <pre>
+const one_second = 10000000; // 1 second in 100ns intervals => 1E7
 var extTimeFlags = readBits(16)
 
 <b>mtime:</b>
 mtime_rmode = extTimeFlags >> 12
 if ((mtime_rmode & 8)==0) goto ctime
 mtime_count = mtime_rmode & 0x3
-mtime_reminder = readBits(8*mtime_count);
+mtime_remainder = readBits(8*mtime_count);
+if ((mtime_rmode & 4)!=0) mtime_remainder += one_second
 
 <b>ctime:</b>
 ctime_rmode = extTimeFlags >> 8
 if ((ctime_rmode & 8)==0) goto atime
-Set ctime to readBits(16)
+Set ctime to readBits(32)
 ctime_count = ctime_rmode & 0x3
-ctime_reminder = readBits(8*ctime_count)
+ctime_remainder = readBits(8*ctime_count)
+if ((ctime_rmode & 4)!=0) ctime_remainder += one_second
 
 <b>atime:</b>
 atime_rmode = extTimeFlags >> 4
 if ((atime_rmode & 8)==0) goto arctime
-Set atime to readBits(16)
+Set atime to readBits(32)
 atime_count = atime_rmode & 0x3
-atime_reminder = readBits(8*atime_count)
+atime_remainder = readBits(8*atime_count)
+if ((atime_rmode & 4)!=0) atime_remainder += one_second
 
 <b>arctime:</b>
 arctime_rmode = extTimeFlags
 if ((arctime_rmode & 8)==0) goto done_exttime
-Set arctime to readBits(16)
+Set arctime to readBits(32)
 arctime_count = arctime_rmode & 0x3
-arctime_reminder = readBits(8*arctime_count)
+arctime_remainder = readBits(8*arctime_count)
+if ((arctime_rmode & 4)!=0) arctime_remainder += one_second
 
 <b>done_exttime</b>
 </pre>
@@ -555,4 +579,4 @@ ZeroCount               4 bits (only present if BitLength is 15)
 </section>
 
 </body>
-</html>
+</html>