id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	launchpad_bug
280	get_hash method in webapi for extension caching logic.	nejucomo	zooko	"The webapi could provide a call which returns the content's hash for a given capability:

get_hash(cap, hashtype) -> hash

cap - A string containing a capability.

hashtype - An enumeration type specifying the hash algorithm; example ""sha256"" (more below).

hash - The result of applying the specified hash to the contents referred to by cap.

Support for different hashtypes allows the backend to implement which ever types are convenient, and extension writers can request specific types for future versions.

As long as the hashtype is convenient for extensions to compute on their own, this allows them to make ""smart"" caching decisions.  For instance, a local file system synchronization command could chose to only download (or upload) a file if get_hash returns a different hash than one computed from the local file.

The tahoe architecture may provide support for certain algorithms efficiently (because they are innate to the data structures).


"	enhancement	assigned	minor	undecided	code-frontend-web	0.7.0		webapi cache extension newcaps	zooko