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Merge branch 'master' of https://github.com/codedread/bitjs

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Jeff Schiller 2022-04-27 13:35:36 -07:00
commit 660810b03d
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@ -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
@ -172,38 +172,78 @@ Packed Data (Total Packed Size) bytes
<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 2: 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>
<li>Bit 3 and 4: The amount of bytes to be read as the remainder, between 0 and 3</li>
</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>
<li>They form a 24-bit integer, sorted from least significant to most significant bits</li>
<li>If fewer than 3 bytes are present, the remaining least significant bits are to be padded with zeroes in order to complete 24-bits</li>
</ul>
</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 = 0
for (var i = 0; i < mtime_count; i++) {
mtime_remainder = (readBits(8) << 16) | (mtime_remainder >> 8)
}
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)
ctime = readBits(32)
ctime_count = ctime_rmode & 0x3
ctime_reminder = readBits(8*ctime_count)
ctime_remainder = 0
for (var i = 0; i < ctime_count; i++) {
ctime_remainder = (readBits(8) << 16) | (ctime_remainder >> 8)
}
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)
atime = readBits(32)
atime_count = atime_rmode & 0x3
atime_reminder = readBits(8*atime_count)
atime_remainder = 0
for (var i = 0; i < atime_count; i++) {
atime_remainder = (readBits(8) << 16) | (atime_remainder >> 8)
}
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)
arctime = readBits(32)
arctime_count = arctime_rmode & 0x3
arctime_reminder = readBits(8*arctime_count)
arctime_remainder = 0
for (var i = 0; i < arctime_count; i++) {
arctime_remainder = (readBits(8) << 16) | (arctime_remainder >> 8)
}
if ((arctime_rmode & 4)!=0) arctime_remainder += one_second
<b>done_exttime</b>
</pre>
@ -551,6 +591,7 @@ ZeroCount 4 bits (only present if BitLength is 15)
<ul>
<li>Eugene Roshal &lt;roshal@rarlab.com&gt; - creator and owner of the RAR format</li>
<li>Jeff Schiller &lt;codedread@gmail.com&gt; - creator of this document as part of the <a href="http://github.com/codedread/bitjs/">bitjs</a> project</li>
<li>Andre Brait &lt;andrebrait@gmail.com&gt; - for documenting the ExtTime structure</li>
</ul>
</section>