128 lines
4.2 KiB
Ruby
128 lines
4.2 KiB
Ruby
# A factory has the one job of handing out new instances
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#
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# A factory is for a specific type (currently, may change by size at some point)
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#
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# get_next_object is the main entry point, all other functions help to get more
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# memory and objects as needed
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#
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# A factory keeps a reserve, and in case the freelist is empty, switches that in _immediately
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# This is especially useful for messages, that can then be used even they run out.
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#
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# The idea (especially for messages) is to call out from the MessageSetup to the
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# factory when the next (not current) is nil.
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# This is btw just as easy a check, as the next needs to be gotten to swap the list.
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module Parfait
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class Factory < Object
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attr_reader :for_type , :next_object , :reserve , :attribute_name , :page_size
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def self.type_length
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6
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end
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def self.memory_size
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8
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end
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# initialize for a given type (for_type). The attribute that is used to create the
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# list is the first that starts with next_ . "next" itself would have been nice and general
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# but is a keyword, so no go.
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def initialize(type , page)
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@for_type = type
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@attribute_name = type.names.find {|name| name.to_s.start_with?("next")}
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@page_size = page
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raise "No next found for #{type.class_name}" unless @attribute_name
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end
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# get the next free object, advancing the list.
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# Calls out to get_more if the list is empty.
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# This function is not realy used, as it is hard-coded in risc, but the get_more is
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# used, as it get's called from risc (or will)
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def get_next_object
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unless( @next_object )
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@next_object = reserve
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get_more
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end
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get_head
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end
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# this gets the head of the freelist, swaps it out agains the next and returns it
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def get_head
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nekst = @next_object
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@next_object = get_next_for(nekst)
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return nekst
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end
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# get more from system
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# and rebuilt the reserve (get_next already instantiates the reserve)
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#
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def get_more
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@reserve = get_chain
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last_link = @reserve
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count = @page_size / 100
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count = 15 if count < 15
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while(count > 0)
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last_link = get_next_for(last_link)
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count -= 1
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end
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@next_object = get_next_for(last_link)
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set_next_for( last_link , nil )
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self
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end
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# this initiates the syscall to get more memory.
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# it creates objects from the mem and link them into a chain
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def get_chain
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raise "type is nil" unless @for_type
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first = sys_mem( for_type , @page_size)
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chain = first
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counter = @page_size
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while( counter > 0)
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nekst = get_next_raw( chain )
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set_next_for(chain, nekst)
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chain = nekst
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counter -= 1
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end
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first
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end
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# get the next_* attribute from the given object.
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# the attribute name is determined in initialize
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def get_next_for(object)
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object.send(attribute_name)
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end
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# set the next_* attribute of the given object, with the value.
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# the attribute name is determined in initialize
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def set_next_for(object , value)
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object.send("_set_#{attribute_name}".to_sym , value)
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end
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# Return the object _after the given one. In memory terms the next object starts
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# after the object ends. So this is in fact pointer arithmetic (once done)
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# This implementation will be moved to the adapter, as the real thing needs to be coded
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# in risc
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# This adapter version just return a new object
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def get_next_raw( object )
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sys_mem( object.get_type , 1)
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end
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# return more memory from the system.
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# Or to be more precise (as that is not really possible), allocate memory
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# for Factory.page_size objects, and return the first object.
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# ( the object has a type as first member, that type will be the for_type of this factory)
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# This implementation will be moved to the adapter, as the real thing needs to be coded
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# in risc
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# This adapter version just return a new object (by establishing the ruby class
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# and using ruby's allocate and set_type)
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def sys_mem( type , amount)
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r_class = eval( "Parfait::#{type.object_class.name}" )
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obj = r_class.allocate
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obj.set_type(type)
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obj
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end
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def to_s
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"Factory:#{for_type.name}"
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end
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end
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end
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