1) "XSWAP contexts" are my new "invention" for Arachne 1.60. They allow
instant garbage collection, and I feel this may be new memory allocation
strategy, although it has probably been invented a thousand times before.
In case it is really my invention, I am publishing the idea (not the
code) under the GNU public license (www.gnu.org) so no one else will have the
right to patent it ;-). So, just in the case I havn't reinvented the wheel...
Anyway, I don't want the story of the LZW algorithm in GIF files to be
repeated.

"Open patent": Memory allocation contexts
-----------------------------------------

Traditional memory allocation strategy is to let programmers call
"malloc(...)" style functions, which allocate memory pages without telling
the memory allocation system any details about future usage and deallocation
of the memory. This means that ANY memory swapping strategy can only produce
random results, not the best possible garbage collection algorithm, since it
is invoked by the "free(...)" function, needs extra CPU time to make the memory
re-usable again, and merges blocks of randomly de-allocated memory.

The XSWAP memory allocation strategy lets programmers specify the context
when allocating memory; at a later time, all memory chunks belonging to a 
certain context can be de-allocated at once at very little CPU time cost 
(it depends only on number of used memory pages, not on the number of items 
being de-allocated). Additionaly, different contexts can be given different 
priority when storing pages of memory using media with different access speeds 
(e.g., RAM vs. disk vs. networked memory).

I declare this algorithm to be publicly known, so no one is allowed
to protect this algorithm by patent laws of any country worldwide.
If you use this algorithm, you are welcome to mention that it is a
re-implementation of XSWAP memory allocation strategy used in the Arachne 
WWW browser. Please contact xchaos@arachne.cz if you are interested.

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2) When running Arachne, the '?' key dumps XSWAP debugging info.
This feature is a kind of Xmas present for Clarence Verge and other
"advanced Arachnologists", who like to compare page load times, etc. ;-)

The debugging information has the following format:

*[s=???, n=???, c=???] (repeated many times) r=???, w=???

where:

* (if present) is the number of the area (1 or 2) where buffer is currently stored
s is the size of buffer in bytes
n is the number of items located in this buffer (tables, lines of text, etc.)
r is the number of buffers reads (from XMS, EMS or disk)
w is the number of written buffers (both r and w will overlow after some time)
c is the context; -1 is an undefined value, other values follow:

#define CONTEXT_HTML   0
#define CONTEXT_SYSTEM 1
#define CONTEXT_TABLES 2
#define CONTEXT_ICONS  3
#define CONTEXT_TMP    4

The XSWAP debugging info can help to analyze some types of problems, e.g.,
very slow Arachne operation, etc. You should never actually see "CONTEXT_TMP"
in this listing, and the number of items (n) in buffers with CONTEXT_TABLES
should be equal to the number of tables in the document (for 0 tables, this context
shouldn't be present at all). Number of HTML atoms Arachne reports
when Alt+M is pressed is NOT identical to the number of items in CONTEXT_HTML.

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3) If Arachne crashes with an "Illegal xSwap operation" message, please
send the details (module name and line number) to xchaos@arachne.cz, but
ONLY IF IT IS A 100% REPRODUCIBLE CRASH !!! - i.e., you are able to
install a clean Arachne, configure it, go online with empty an cache if crash
was caused by an online page, and then reproduce the crash exactly at any time.