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Diffstat (limited to 'doc/protocol-suggestion.txt')
| -rw-r--r-- | doc/protocol-suggestion.txt | 71 |
1 files changed, 0 insertions, 71 deletions
diff --git a/doc/protocol-suggestion.txt b/doc/protocol-suggestion.txt deleted file mode 100644 index 531d6cd5..00000000 --- a/doc/protocol-suggestion.txt +++ /dev/null @@ -1,71 +0,0 @@ -Subscription ------------- - -The subscription mechanism would involve sending a Subscribe() -(preferably without reply) message to the subscriber, and one AddMatch() -message to the D-Bus daemon for each property subscribed. Unsubscribing -is similarly straightforward. - -This is based on the fact that the provider mainly is interested in the -fact whether there exists someone at all interested in their exposed -properties. - -However, to handle ungraceful subscribers who don't send Unsubscribe() -messages when they go away, the provider needs to know its peers. It -can do so by maintaining an association of property => subscribers -(using the unique D-Bus name of the sender as subscriber). On receipt -of an Unsubscribe() message, or a NameOwnerChanged() signal, it needs to -check if the sender was subscribed to some properties and remove it from -the mapping. If noone is interested in a property, it should cease -updating the property to save resources. - -Signaling changes ------------------ - -Properties would be represented as object paths. A subscriber emits a -ValueChanged() signal whenever a value changes. - -One concern is the number of match rules in the D-Bus daemon. This -approach effectively means one rule per each (subscriber, property) -pair, contrary to the current way of one rule per subscriber. - -Suspending notifications - - -Commanding ----------- - -Performance speculations ------------------------- - -However the number of messages - -With the current implementation, for N subscribers, there are N messages -emitted (with different object paths). Including the hops between the -D-Bus daemon that totals in 2*N messages, with the D-Bus daemon having -to dispatch N incoming messages. Using the new scheme it's only N+1 -messages, and the daemon only has to dispatch 1 message. - -The D-Bus interface -------------------- - -METHOD VOID Subscribe(ARRAY OF STRING properties) - -[ If a subscriber needs to immediately get the value of a property, it - should call the Get() method. ] - -SIGNAL ValueChanged(BOOL unknownp, VARIANT value) - -[ The old signature obviously has to change, as now we don't try to - bundle several properties into one message. If the first boolean - argument determines whether the value is known or unknown. In the - latter case, the second argument is to be ignored. Alternatively, the - unknown value could be represented specially, like an emtpy STRUCT on - D-Bus, then the BOOL is omitted. ] - -METHOD VOID Unsubscribe(ARRAY OF STRING properties) - -METHOD VARIANT Get(STRING property) - -[ The provider shall _immediately_ return whatever value it has for the - named property. If it's unknown, then that, but it must not block. ] |