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    <p>I don't have the time to write it for you (not too sure your sample is actually complete enough to do so) but if you must, I can think of</p> <ul> <li><p>using translation tables for the various input/output bit shift offsets; This optimization would make sense for fixed units of <code>n</code> bits (with <code>n</code> sufficiently large (8 bits?) to expect performance gains) In essence, you'd be able to do</p> <pre><code>destloc &amp;= (lookuptable[bits_left_in_buffer][input_offset][codeword]); </code></pre></li> </ul> <p><em>disclaimer: this is very sloppy pseudo code, I just hope it conveys my idea of a lookup table o prevent bitshift arithmetics</em></p> <ul> <li>writing it in assembly (I know i386 has <a href="http://faydoc.tripod.com/cpu/xlat.htm" rel="nofollow"><code>XLAT</code></a>, but then again, a good compiler might already use something like that) ; Also, XLAT seems limited to 8 bits and the AL register, so it's not really versatile</li> </ul> <h2>Update</h2> <p><strong>Warning</strong>: be sure to use a profiler and test your optimization for correctness and speed. Using a lookup table <em>can</em> result in poorer performance in the light of locality of reference. So, you might need to change the bit-streaming thread on a single core (set thread affinity) to get the benefits, and you might have to adapt the lookup table size to the processor's L2 cache.</p> <p>Als, have a look at <a href="http://users.telenet.be/tfautre/softdev/simd/" rel="nofollow">SIMD</a>, <a href="http://en.wikipedia.org/wiki/SSE4" rel="nofollow">SSE4</a> or <a href="http://developer.nvidia.com/cuda-downloads" rel="nofollow">GPU (CUDA)</a> instruction sets if you <em>know</em> you'll have certain features at your disposal. </p>
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    1. POfastest way to write a bitstream on modern x86 hardware
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    1. COadded references to libs for specific instruction sets
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    2. COSSE is useless for bitstream stuff on account of not having a properly vectorized shift (it can only shift 128bit values by whole bytes, and can only shift packed types by the same amount across the entire register)
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    3. COLookup tables are interesting. In my experience "in-place" processing tends to be quicker than look-up tables (for low-level operations) on modern machines, so I'm not convinced. I'll be sure to give it a try though to see how it preforms.
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