92 lines
2.7 KiB
Ruby
92 lines
2.7 KiB
Ruby
# An Object is really a hash like structure. It is dynamic and
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# you want to store values by name (instance variable names).
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#
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# One could (like mri), store the names in each object, but that is wasteful
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# Instead we store only the values, and access them by index.
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# The Layout allows the mapping of names to index.
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# The Layout of an object describes the memory layout of the object
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# The Layout is a simple list of the names of instance variables.
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#
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# As every object has a Layout to describe it, the name "layout" is the
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# first name in the list for every Layout.
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# But as we want every Object to have a class, the Layout carries that class.
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# So the layout of layout has an entry "object_class"
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# In other words, the Layout is a list of names that describe
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# the values stored in an actual object.
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# The object is an List of values of length n and
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# the Layout is an List of names of length n
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# Together they turn the object into a hash like structure
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module Parfait
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class Layout < List
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attribute :object_class
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def initialize( object_class )
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super()
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self.object_class = object_class
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end
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def == other
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self.object_id == other.object_id
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end
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# add the name of an instance variable
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# The index will be returned and can subsequently be searched with index_of
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# The index of the name is the index of the data in the object
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#
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# TODO , later we would need to COPY the layout to keep the old constant
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# but now we are concerned with booting, ie getting a working structure
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def add_instance_variable name
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self.push(1) if self.get_length == 0
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self.push(name)
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self.get_length
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end
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def object_instance_names
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names = List.new
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index = 3
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while index <= self.get_length
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item = get(index)
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names.push item
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index = index + 1
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end
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names
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end
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alias :list_index :index_of
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# private inheritance is something to think off, we don't really want the list api exported
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def index_of name
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raise "should not rely on layout internal structure, use variable_index"
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end
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# index of a variable name into the layout.
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# layout is a list, so lowest index is 1
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# :layout is a variable for every object, so 1 is taken for :layout
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# still, the index is the same.
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def variable_index name
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list_index(name)
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end
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def inspect
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ret = "Layout["
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index = 3
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while index <= self.get_length
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item = get(index)
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ret += item.inspect
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ret += "," unless index == self.get_length
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index = index + 1
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end
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ret += "]"
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ret
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end
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def sof_reference_name
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"#{self.object_class.name}_Layout"
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end
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end
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end
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