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explanations

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psyc://psyced.org/~lynX 2011-05-24 21:24:15 +02:00
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@ -129,7 +129,8 @@ We'll use the latter here:
* Results
Parsing time of 1 000 000 packets, in milliseconds.
a simple strlen scan of the respective message is provided for comparison.
A simple strlen() scan of the respective message is provided for comparison.
These tests were performed on a 2.53 GHz Intel(R) Core(TM)2 Duo P9500 CPU.
| input: | PSYC | | JSON | | | XML | |
| parser: | strlen | libpsyc | json-c | json-glib | libxml sax | libxml | rapidxml |
@ -169,8 +170,17 @@ not performed.
| / | < | > | < | > | < | | > |
| <r> | | | | | | | |
* Explanations
These tests were performed on a 2.53 GHz Intel(R) Core(TM)2 Duo P9500 CPU.
As you can tell the PSYC data format outpaces its rivals in all circumstances.
Extremely so when delivering binary data as PSYC simply returns the starting
point and the length of the given buffer while the other parsers have to scan
for the end of the transmission, but also with many simpler operations, when
PSYC quickly figures out where the data starts and ends and passes such
information back to the application while the other formats are forced to
generate a copy of the data in order to process possibly embedded special
character sequences. PSYC essentially operates like a binary data protocol
even though it is actually still text-based.
* Criticism
@ -186,6 +196,8 @@ In fact we are looking into suitable syntax extensions to represent
generic structures and semantic signatures, but for now PSYC only
provides for simple typed values and lists of typed values.
* Ease of implementation
Another aspect is the availability of these formats for spontaneous
use. You could generate and parse JSON yourself but you have to be
careful about escaping. XML can be rendered manually if you know your
@ -194,6 +206,15 @@ a bullet proof parser. PSYC is easy to render and parse yourself for
simple tasks, as long as your body does not contain "\n|\n" and your
variables do not contain newlines.
* Caveats
In every case we'll compare performance of parsing and re-rendering
these messages, but consider also that the applicative processing
of an XML DOM tree is more complicated than just accessing
certain elements in a JSON data structure or PSYC variable mapping.
* Conclusions
After all it is up to you to find out which format fulfils your
requirements the best. We use PSYC for the majority of messaging where
JSON and XMPP aren't efficient and opaque enough, but we employ XML and
@ -201,22 +222,6 @@ JSON as payloads within PSYC for data that doesn't fit the PSYC model.
For some reason all three formats are being used for messaging, although
only PSYC was actually designed for that purpose.
* Caveats
In every case we'll compare performance of parsing and re-rendering
these messages, but consider also that the applicative processing
of an XML DOM tree is more complicated than just accessing
certain elements in a JSON data structure or PSYC variable
mapping.
For a speed check in real world conditions which also consider the
complexity of processing incoming messages we should compare
the performance of a chat client using the two protocols,
for instance by using libpurple with XMPP and PSYC accounts.
To this purpose we first need to integrate libpsyc into libpurple.
* Conclusions
The Internet has developed two major breeds of protocol formats.
The binary ones are extremely efficient but usually not very flexible
(unless you are willing to recompile all instances each time you