util.dbuffer: Add efficient shortcuts for discard() in certain cases
If the buffer is already empty, nothing to do. If we're throwing away the
whole buffer, we can just empty it and avoid read_chunk() (which in turn
may collapse()). These shortcuts are much more efficient.
-- luacheck: ignore 212
local driver = {};
local driver_mt = { __index = driver };
function driver:open(store, typ)
if typ and typ ~= "keyval" and typ ~= "archive" then
return nil, "unsupported-store";
end
return setmetatable({ store = store, type = typ }, driver_mt);
end
function driver:get(user)
return {};
end
function driver:set(user, data)
return nil, "Storage disabled";
end
function driver:stores(username)
return { "roster" };
end
function driver:purge(user)
return true;
end
function driver:append()
return nil, "Storage disabled";
end
function driver:find()
return function () end, 0;
end
function driver:delete()
return true;
end
module:provides("storage", driver);