48 lines
1.5 KiB
Ruby
48 lines
1.5 KiB
Ruby
module Vm
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# Base class for anything that we can assemble
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# Derived classes include instructions and constants(data)
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# The commonality abstracted here is the length and position
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# and the ability to assemble itself into the stream(io)
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# All code is position independant once assembled.
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# But for jumps and calls two passes are neccessary.
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# The first setting the position, the second assembling
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class Code
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def class_for clazz
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RegisterMachine.instance.class_for(clazz)
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end
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# set the position to zero, will have to reset later
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def initialize
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@position = 0
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end
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# the position in the stream. Think of it as an address if you want. The difference is small.
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# Especially since we produce _only_ position independant code
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# in other words, during assembly the position _must_ be resolved into a pc relative address
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# and not used as is
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def position
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@position
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end
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# The containing class (assembler/function) call this to tell the instruction/data where it is in the
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# stream. During assembly the position is then used to calculate pc relative addresses.
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def link_at address , context
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@position = address
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end
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# length for this code in bytes
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def length
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raise "Not implemented #{inspect}"
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end
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# we pass the io (usually string_io) in for the code to assemble itself.
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def assemble(io)
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raise "Not implemented #{self.inspect}"
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end
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end
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end |