45 lines
1.5 KiB
Ruby
45 lines
1.5 KiB
Ruby
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module Asm
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# Base class for anything that we can assemble
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# Derived classes include instructions and data(strings)
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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
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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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# just sets position to nil, so we can sell that it has not been set
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def initialize
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@position = nil
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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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throw "Not set" unless @address
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@address
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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 at address
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@address = 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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throw "Not implemented #{self}"
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end
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# so currently the interface passes the io (usually string_io) in for the code to assemble itself.
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# this may change as the writing is still done externally (or that will change)
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def assemble(io)
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throw "Not implemented #{self}"
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end
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end
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end
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