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267 lines
11 KiB
267 lines
11 KiB
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
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<html>
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<head>
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<title>What's new in this release of LKRhash?</title>
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<link rel=Stylesheet type="text/css" media=all href="./docs/lkr.css">
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</head>
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<body>
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<h1>What's new in this release of LKRhash?</h1>
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<ul>
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<li> <a href="#dec2000"> December 2000</a></li>
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<li> <a href="#2000-07-31"> 2000/07/31</a></li>
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<li> <a href="#2000-04-24"> 2000/04/24</a></li>
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<li> <a href="#2000-03-22"> 2000/03/22</a></li>
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<li> <a href="#1999-11-04"> 1999/11/04</a></li>
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</ul>
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<a name="dec2000">
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<h2>December 2000</h2>
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</a>
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<ul>
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<li> Refactored the code.</li>
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<li> Public API.</li>
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<li> C API.</li>
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<li> Kernel-mode support.</li>
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<li> Fixed a deadlock bug in the table lock. If you explicitly
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call <code>Table::ReadLock</code> and
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<code>Table::WriteLock</code>, you <strong>need</strong> this fix,
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or you will deadlock under stress.</li>
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<li> Fixed a bug in table compaction: until now, the table
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never actually compacted after elements were deleted, as
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the test for compaction always evaluated to `false'.</li>
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<li> Changed the name of <code>EqualKeys</code> to
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<code>CompareKeys</code>, which now returns an
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<code>int</code> instead of a <code>bool</code>. This is
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needed for multikeys support.
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<li> Changed the signature of <code>AddRefRecord</code>. The
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second parameter is now an <code>LK_ADDREF_REASON</code>,
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instead of an <code>int</code> whose value is
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<code>+1</code> or <code>-1</code>. The reason code
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aids in debugging refcount leaks. If its value is negative, the
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refcount should be decremented; otherwise the refcount
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should be incremented. Also, <code>AddRefRecord</code>
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now returns <code>LONG</code> instead of
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<code>void</code>: the new value of the reference count.</li>
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<li> Changed behavior of <code>ApplyIf</code> locking: now
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locks one subtable at a time, instead of all
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subtables. Can use <code>Table::ReadLock</code> or
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<code>Table::WriteLock</code> to retain old behavior.</li>
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<li> Changed names and signatures of
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<code>void LKRHashTableInit()</code> and
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<code>void LKRHashTableUninit()</code>, to
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<code>BOOL LKR_Initialize(DWORD)</code> and
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<code>void LKR_Terminate()</code>, respectively.</li>
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<li> Fixed <code>iterator::operator*()</code> and
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<code>iterator::operator->()</code>.</li>
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</ul>
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<a name="2000-07-31">
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<h2>2000/07/31</h2>
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</a>
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<ul>
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<li> <strong>Really</strong> fixed the bug in <code>Clear</code> that left
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certain internal state variables in an inconsistent state. If
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you later inserted/deleted enough new records, LKRhash would
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AV. (The fix in the 2000/03/22 release did not work in all
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cases.)</li>
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</ul>
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<a name="2000-04-24">
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<h2>2000/04/24</h2>
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</a>
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<ul>
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<li> I added support for STL-style iterators
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<ul>
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<li> New iterators <strong>do not lock</strong> the table or
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a bucket chain. In a multithreaded situation, it is
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<strong>your</strong> responsibility to call
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<code>WriteLock</code> (or <code>ReadLock</code>) on the
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table before initializing any iterators, and to call
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<code>WriteUnlock</code> (or <code>ReadUnlock</code>)
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when you are finished.</li>
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<li> The table provides <code>begin()</code> and
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<code>end()</code> methods. As the compiler isn't quite
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smart enough to realize that <code>end()</code> always
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returns a trivial empty iterator, a loop such as
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<pre>
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MyTable::iterator iter;
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for (iter = pTbl->begin(); iter != pTbl->end(); ++iter) ...
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</pre>
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is more efficiently expressed as
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<pre>
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MyTable::iterator iter;
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MyTable::iterator iterEnd = pTbl->end();
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for (iter = pTbl->begin(); iter != iterEnd; ++iter) ...
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</pre></li>
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<li> iterators can be pre- and post-incremented; i.e.:
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<code>++iter</code> and <code>iter++</code>.
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Pre-increment is more efficient than post-increment.</li>
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<li> Table provides a constructor that accepts a range of
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iterators into another container.</li>
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<li> Provides an <code>Insert</code> method that returns an iterator,
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pointing to the newly inserted record, or <code>end()</code> on
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failure.</li>
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<li> Provides a <code>Find</code> method that returns an iterator
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pointing to the record with the passed-in key, or
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<code>end()</code> on failure.</li>
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<li> Provides an <code>EqualRange</code> method that returns
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two iterators describing the range that contain all the
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records whose keys match the passed-in key. Until full
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support for multiple, identical keys is added, the range
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will contain either zero or one record(s).</li>
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<li> Provides an <code>Erase</code> method that deletes the
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record pointed to by the iterator. Updates the iterator to
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point to the next record in the table.</li>
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<li> Provides an <code>Erase</code> method that takes two
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iterators, which will delete all the records in the range
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described by the two iterators.</li>
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<li> Unlike the old, deprecated iterators (<code>CIterator</code>),
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more than one iterator can be active at a time. It is
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best not to call the non-iterator insert/delete methods
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(<code>InsertRecord</code>, <code>DeleteRecord</code>,
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<code>DeleteKey</code>) while iterators are open, as the
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non-iterator methods can rebalance bucket chains,
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leading to invalid iterators, undercounting, and/or
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overcounting. This is true even if the table was
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WriteLocked, before the iterators were initialized. It
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is best to use the iterator <code>Insert</code> or
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<code>Erase</code> methods in such a case.</li>
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<li> The iterators are reference-counted.</li>
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</ul>
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</li>
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<li> I have provided an NTSD/CDB debugger extension, <i>lkrdbg.dll</i>,
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with one method, <code>!lkrdbg.lkrhash</code>:
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<ul>
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<li> <code>!lkrhash -l[0-2] <i>addr</i></code> will dump the
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hashtable at <code><i>addr</i></code> at verbosity level
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<code>l</code> (default 0).</li>
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<li> <code>!lkrhash -g[0-2]</code> will dump ALL hashtables
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at at verbosity level <code>l</code> (default 0).</li>
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<li> I have provided an easy-to-use customization mechanism in
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<i>lkrcust.h</i> to provide custom dumps for different
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hashtables. It's keyed off the <code>pszName</code> parameter
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used in the hashtable constructor. You can provide a custom dump
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routine for the table (to dump whatever other fields you
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might have added), as well as a custom dump routine for
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the record class stored by the hashtable. Provided three
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examples of customization, based on the samples.</li>
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</ul>
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</li>
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<li> Fixed various build issues
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<ul>
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<li> All debug code is now bracketed with <code>#ifdef
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IRTLDEBUG</code> (instead of <code>#ifdef _DEBUG</code>).
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Currently equivalent, but you can control this in
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<i>irtldbg.h</i></li>
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<li> Fix all Unicode build issues. Code is now TCHAR-aware.</li>
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<li> Added <i>lkrhash.rc</i> to provide a version resource</li>
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</ul>
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</li>
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<li> Turned on <code>LKRhash</code> and <code>HashFn</code>
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namespaces by default. See <i>readme.txt</i>.</li>
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<li> Reorganized the samples into their own subtree.</li>
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<li> Removed more old code that used to be present so that I could
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test some changes (e.g., stuff bracketed by
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<code>LKR_OLD_SEGMENT</code>, <code>LKR_SIGS_NODES</code>,
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etc).</li>
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<li> Bucket Lock is once again <code>CSmallSpinLock</code>, unless
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<code>LKR_DEPRECATED_ITERATORS</code> is defined (off by
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default).</li>
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<li> Moved a lot of nested classes out of the table classes, to be
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top-level classes.</li>
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<li> Better compile-time and run-time assertions.</li>
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</ul>
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<a name="2000-03-22">
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<h2>2000/03/22</h2>
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</a>
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<ul>
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<li> Fixed a bug in <code>Clear</code> that left certain
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internal state variables in an inconsistent state. If you
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later inserted/deleted enough new records, LKRhash would AV.</li>
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<li> Changed <code>BucketLock</code> to <code>CReaderWriterLock3</code>
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(recursive MRSW lock) to support certain scenarios, such as
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being able to call <code>FindKey</code> while enumerating
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with an old-style iterator. Slightly slower, but the speed
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improvements below more than compensate.</li>
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<li> Removed the 300-line example from the end of lkrhash.h. Now in
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hashtest.cpp, bracketed by <code>SAMPLE_LKRHASH_TESTCLASS</code>.</li>
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<li> Replaced <code>TRACE</code> macro with
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<code>IRTLTRACE</code> so as not to interfere with other
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<code>TRACE</code> macros (e.g., MFC's).</li>
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<li> Added <i>dirs</i> and <i>sources</i> files so that you
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can build LKRhash with the NT build environment.</li>
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<li> Added <code>STATIC_ASSERT</code> macro for compile-time
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assertions. The <code>IRTLASSERT</code> macro is still used
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for run-time assertions.</li>
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<li> Removed old code that used to be present so that I could test
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some changes (e.g., stuff bracketed by
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<code>LKR_NEWCODE</code>, <code>LKR_MASK</code>,
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<code>LKR_SUBTABLE</code>,
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<code>LKR_COMPACT_DELETE</code>, etc).</li>
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<li> Upped <code>LK_DFLT_MAXLOAD</code> to 6
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(<code>NODES_PER_CLUMP</code>) to get better memory usage.</li>
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<li> Added support for RockAll (not enabled by default)</li></li>
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<li> Turned <code>CSegment</code> into a concrete base
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class. Somewhat hacky but faster.</li>
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<li> Made the locks a little faster, esp.
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<code>CReaderWriterLock3::IsWriteLocked</code>.</li>
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<li> Experimented with countdown loops (turned out to be slightly
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slower).</li>
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<li> Experimented with bitwise scrambling for subtable index
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calculation. Faster.</li>
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<li> Experimented with using a bitwise mask for subtable index
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calculation. Faster.</li>
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<li> Removed some inlines from <i>lkrhash.h</i> to improve modularity.</li>
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<li> Removed unimplemented <code>Print</code> methods.</li>
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<li> Bracketed global lists of hashtables with
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<code>LKR_NO_GLOBAL_LIST</code>.</li>
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<li> Reduced number of subtables to min(1, #CPUs) for
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<code>LK_SMALL_TABLESIZE</code> Was min(2, #CPUs). Max number
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of subtables is now 64.</li>
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</ul>
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<a name="1999-11-04">
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<h2>1999/11/04</h2>
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</a>
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<ul>
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<li> New reader-writer locks.</li>
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<li> Smarter, faster simple spinlocks.</li>
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<li> compact delete.</li>
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<li> debugging support.</li>
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<li> increased default load factor from 4.0 to 5.0 after
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reducing size of spinlock => reduced memory usage.</li>
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<li> deprecated CIterator.</li>
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<li> better error checking.</li>
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<li> Win64 clean.</li>
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<li> expose table locks => composition of operations.</li>
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<li> global list.</li>
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<li> faster hash scrambling function..</li>
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<li> won't fail messily in low-memory situations.</li>
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<li> fixed a race condition in some of the assertions.</li>
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<li> enhanced test program.</li>
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</ul>
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<hr>
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<address></address>
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<!-- hhmts start -->
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Last modified: Sat Nov 25 20:41:23 2000
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<!-- hhmts end -->
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</body>
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</html>
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