3eb933400a
there are some cases that may lead to inconsistencies. Currently, only the master-slave method is a reliable sync method
224 lines
7.2 KiB
CoffeeScript
224 lines
7.2 KiB
CoffeeScript
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#
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# @nodoc
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# An object that holds all applied operations.
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#
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# @note The HistoryBuffer is commonly abbreviated to HB.
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#
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class HistoryBuffer
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#
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# Creates an empty HB.
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# @param {Object} user_id Creator of the HB.
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#
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constructor: (@user_id)->
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@operation_counter = {}
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@buffer = {}
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@change_listeners = []
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@garbage = [] # Will be cleaned on next call of garbageCollector
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@trash = [] # Is deleted. Wait until it is not used anymore.
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@performGarbageCollection = true
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@garbageCollectTimeout = 30000
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@reserved_identifier_counter = 0
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setTimeout @emptyGarbage, @garbageCollectTimeout
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resetUserId: (id)->
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own = @buffer[@user_id]
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if own?
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for o_name,o of own
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if o.uid.creator?
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o.uid.creator = id
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if o.uid.alt?
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o.uid.alt.creator = id
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if @buffer[id]?
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throw new Error "You are re-assigning an old user id - this is not (yet) possible!"
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@buffer[id] = own
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delete @buffer[@user_id]
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if @operation_counter[@user_id]?
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@operation_counter[id] = @operation_counter[@user_id]
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delete @operation_counter[@user_id]
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@user_id = id
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emptyGarbage: ()=>
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for o in @garbage
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#if @getOperationCounter(o.uid.creator) > o.uid.op_number
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o.cleanup?()
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@garbage = @trash
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@trash = []
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if @garbageCollectTimeout isnt -1
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@garbageCollectTimeoutId = setTimeout @emptyGarbage, @garbageCollectTimeout
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undefined
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#
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# Get the user id with wich the History Buffer was initialized.
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#
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getUserId: ()->
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@user_id
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addToGarbageCollector: ()->
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if @performGarbageCollection
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for o in arguments
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if o?
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@garbage.push o
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stopGarbageCollection: ()->
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@performGarbageCollection = false
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@setManualGarbageCollect()
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@garbage = []
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@trash = []
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setManualGarbageCollect: ()->
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@garbageCollectTimeout = -1
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clearTimeout @garbageCollectTimeoutId
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@garbageCollectTimeoutId = undefined
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setGarbageCollectTimeout: (@garbageCollectTimeout)->
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#
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# I propose to use it in your Framework, to create something like a root element.
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# An operation with this identifier is not propagated to other clients.
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# This is why everybode must create the same operation with this uid.
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#
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getReservedUniqueIdentifier: ()->
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{
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creator : '_'
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op_number : "_#{@reserved_identifier_counter++}"
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doSync: false
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}
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#
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# Get the operation counter that describes the current state of the document.
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#
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getOperationCounter: (user_id)->
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if not user_id?
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res = {}
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for user,ctn of @operation_counter
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res[user] = ctn
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res
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else
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@operation_counter[user_id]
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isExpectedOperation: (o)->
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@operation_counter[o.uid.creator] ?= 0
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o.uid.op_number <= @operation_counter[o.uid.creator]
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true #TODO: !! this could break stuff. But I dunno why
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#
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# Encode this operation in such a way that it can be parsed by remote peers.
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# TODO: Make this more efficient!
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_encode: (state_vector={})->
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json = []
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unknown = (user, o_number)->
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if (not user?) or (not o_number?)
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throw new Error "dah!"
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not state_vector[user]? or state_vector[user] <= o_number
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for u_name,user of @buffer
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# TODO next, if @state_vector[user] <= state_vector[user]
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for o_number,o of user
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if (not o.uid.noOperation?) and o.uid.doSync and unknown(u_name, o_number)
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# its necessary to send it, and not known in state_vector
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o_json = o._encode()
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if o.next_cl? # applies for all ops but the most right delimiter!
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# search for the next _known_ operation. (When state_vector is {} then this is the Delimiter)
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o_next = o.next_cl
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while o_next.next_cl? and unknown(o_next.uid.creator, o_next.uid.op_number)
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o_next = o_next.next_cl
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o_json.next = o_next.getUid()
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else if o.prev_cl? # most right delimiter only!
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# same as the above with prev.
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o_prev = o.prev_cl
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while o_prev.prev_cl? and unknown(o_prev.uid.creator, o_prev.uid.op_number)
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o_prev = o_prev.prev_cl
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o_json.prev = o_prev.getUid()
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json.push o_json
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json
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#
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# Get the number of operations that were created by a user.
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# Accordingly you will get the next operation number that is expected from that user.
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# This will increment the operation counter.
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#
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getNextOperationIdentifier: (user_id)->
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if not user_id?
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user_id = @user_id
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if not @operation_counter[user_id]?
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@operation_counter[user_id] = 0
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uid =
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'creator' : user_id
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'op_number' : @operation_counter[user_id]
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'doSync' : true
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@operation_counter[user_id]++
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uid
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#
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# Retrieve an operation from a unique id.
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#
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# when uid has a "sub" property, the value of it will be applied
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# on the operations retrieveSub method (which must! be defined)
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#
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getOperation: (uid)->
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if uid.uid?
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uid = uid.uid
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o = @buffer[uid.creator]?[uid.op_number]
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if uid.sub? and o?
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o.retrieveSub uid.sub
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else
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o
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#
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# Add an operation to the HB. Note that this will not link it against
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# other operations (it wont executed)
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#
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addOperation: (o)->
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if not @buffer[o.uid.creator]?
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@buffer[o.uid.creator] = {}
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if @buffer[o.uid.creator][o.uid.op_number]?
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throw new Error "You must not overwrite operations!"
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if (o.uid.op_number.constructor isnt String) and (not @isExpectedOperation(o)) and (not o.fromHB?) # you already do this in the engine, so delete it here!
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throw new Error "this operation was not expected!"
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@addToCounter(o)
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@buffer[o.uid.creator][o.uid.op_number] = o
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o
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removeOperation: (o)->
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delete @buffer[o.uid.creator]?[o.uid.op_number]
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# When the HB determines inconsistencies, then the invokeSync
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# handler wil be called, which should somehow invoke the sync with another collaborator.
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# The parameter of the sync handler is the user_id with wich an inconsistency was determined
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setInvokeSyncHandler: (f)->
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@invokeSync = f
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# empty per default # TODO: do i need this?
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invokeSync: ()->
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# after you received the HB of another user (in the sync process),
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# you renew your own state_vector to the state_vector of the other user
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renewStateVector: (state_vector)->
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for user,state of state_vector
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if ((not @operation_counter[user]?) or (@operation_counter[user] < state_vector[user])) and state_vector[user]?
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@operation_counter[user] = state_vector[user]
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#
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# Increment the operation_counter that defines the current state of the Engine.
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#
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addToCounter: (o)->
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if not @operation_counter[o.uid.creator]?
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@operation_counter[o.uid.creator] = 0
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if typeof o.uid.op_number is 'number' and o.uid.creator isnt @getUserId()
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# TODO: check if operations are send in order
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if o.uid.op_number is @operation_counter[o.uid.creator]
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@operation_counter[o.uid.creator]++
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else
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@invokeSync o.uid.creator
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#if @operation_counter[o.uid.creator] isnt (o.uid.op_number + 1)
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#console.log (@operation_counter[o.uid.creator] - (o.uid.op_number + 1))
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#console.log o
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#throw new Error "You don't receive operations in the proper order. Try counting like this 0,1,2,3,4,.. ;)"
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module.exports = HistoryBuffer
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