62 lines
1.7 KiB
Ruby
62 lines
1.7 KiB
Ruby
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module Vm
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# constants are the stuff that you embedd in the program as numbers or strings.
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# Another way to think about them is as Operands, they have no seperate "identity"
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# and usually end up embedded in the instructions. ie your basic foo + 4 will encode
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# the 4 in the instruction opcode. The 4 is not accessible anywhere else.
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# When it should be usable in other forms, the constant must become a Value first
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class Constant < Code
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end
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# another abstract "marker" class (so we can check for it)
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# derived classes are Boot/Meta Clas and StringConstant
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class ObjectConstant < Constant
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end
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class IntegerConstant < Constant
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def initialize int
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@integer = int
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end
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attr_reader :integer
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def value
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@integer
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end
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def to_asm
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@integer.to_s
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end
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end
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# The name really says it all.
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# The only interesting thing is storage.
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# Currently string are stored "inline" , ie in the code segment.
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# Mainly because that works an i aint no elf expert.
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class StringConstant < ObjectConstant
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attr_reader :string
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# currently aligned to 4 (ie padded with 0) and off course 0 at the end
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def initialize str
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str = str.to_s if str.is_a? Symbol
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length = str.length
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# rounding up to the next 4 (always adding one for zero pad)
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pad = ((length / 4 ) + 1 ) * 4 - length
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raise "#{pad} #{self}" unless pad >= 1
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@string = str + " " * pad
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end
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def result= value
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class_for(MoveInstruction).new(value , self , :opcode => :mov)
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end
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# the strings length plus padding
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def length
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string.length
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end
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# just writing the string
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def assemble(io)
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io << string
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end
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end
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end
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