This class implements the JPEG 2000 entropy coder, which codes stripes in code-blocks. This entropy coding engine can function in a single-threaded mode where one code-block is encoded at a time, or in a multi-threaded mode where multiple code-blocks are entropy coded in parallel. The interface presented by this class is the same in both modes.

       <p>The number of threads used by this entropy coder is specified by the
       "jj2000.j2k.entropy.encoder.StdEntropyCoder.nthreads" Java system
       property. If set to "0" the single threaded implementation is used. If set
       to 'n' ('n' larger than 0) then 'n' extra threads are started by this class
       which are used to encode the code-blocks in parallel (i.e. ideally 'n'
       code-blocks will be encoded in parallel at a time). On multiprocessor
       machines under a "native threads" Java Virtual Machine implementation each
       one of these threads can run on a separate processor speeding up the
       encoding time. By default the single-threaded implementation is used. The
       multi-threaded implementation currently assumes that the vast majority of
       consecutive calls to 'getNextCodeBlock()' will be done on the same
       component. If this is not the case, the speed-up that can be expected on
       multiprocessor machines might be significantly decreased.</p><p>The code-blocks are rectangular, with dimensions which must be powers of
       2. Each dimension has to be no smaller than 4 and no larger than 256. The
       product of the two dimensions (i.e. area of the code-block) may not exceed
       4096.</p><p>Context 0 of the MQ-coder is used as the uniform one (uniform,
       non-adaptive probability distribution). Context 1 is used for RLC
       coding. Contexts 2-10 are used for zero-coding (ZC), contexts 11-15 are
       used for sign-coding (SC) and contexts 16-18 are used for
       magnitude-refinement (MR).</p><p>This implementation buffers the symbols and calls the MQ coder only once
       per stripe and per coding pass, to reduce the method call overhead.</p><p>This implementation also provides some timing features. They can be
       enabled by setting the 'DO_TIMING' constant of this class to true and
       recompiling. The timing uses the 'System.currentTimeMillis()' Java API
       call, which returns wall clock time, not the actual CPU time used. The
       timing results will be printed on the message output. Since the times
       reported are wall clock times and not CPU usage times they can not be added
       to find the total used time (i.e. some time might be counted in several
       places). When timing is disabled ('DO_TIMING' is false) there is no penalty
       if the compiler performs some basic optimizations. Even if not the penalty
       should be negligeable.</p><p>The source module must implement the CBlkQuantDataSrcEnc interface and
       code-block's data is received in a CBlkWTData instance. This modules sends
       code-block's information in a CBlkRateDistStats instance.</p>