104 lines
4.1 KiB
Ruby
104 lines
4.1 KiB
Ruby
module Virtual
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# The Virtual Machine is a value based virtual machine in which ruby is implemented. While it is value based,
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# it resembles oo in basic ways of object encapsulation and method invokation, it is a "closed" / static sytem
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# in that all types are know and there is no dynamic dispatch (so we don't bite our tail here).
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#
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# It is minimal and realistic and low level
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# - minimal means that if one thing can be implemented by another, it is left out. This is quite the opposite from
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# ruby, which has several loops, many redundant if forms and the like.
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# - realistic means it is easy to implement on a 32 bit machine (arm) and possibly 64 bit. Memory access, a stack,
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# some registers of same size are the underlying hardware. (not ie byte machine)
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# - low level means it's basic instructions are realively easily implemented in a register machine. ie send is not
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# a an instruction but a function.
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#
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# So the memory model of the machine allows for indexed access into an "object" . A fixed number of objects exist
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# (ie garbage collection is reclaming, not destroying and recreating) although there may be a way to increase that number.
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#
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# The ast is transformed to virtaul-machine objects, some of which represent code, some data.
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#
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# The next step transforms to the register machine layer, which is what actually executes.
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#
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# More concretely, a virtual machine is a sort of oo turing machine, it has a current instruction, executes the
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# instructions, fetches the next one and so on.
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# Off course the instructions are not soo simple, but in oo terms quite so.
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#
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# The machine is virtual in the sense that it is completely modeled in software,
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# it's complete state explicitly available (not implicitly by walking stacks or something)
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# The machine has a no register, but local variables, a scope at each point in time.
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# Scope changes with calls and blocks, but is saved at each level. In terms of lower level implementation this means
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# that the the model is such that what is a variable in ruby, never ends up being just on the pysical stack.
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#
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class Machine
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def initialize
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@parser = Parser::Salama.new
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@passes = [ "Virtual::SendImplementation" ]
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end
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attr_reader :message , :passes , :space , :class_mappings , :init
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def run_passes
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@passes.each do |pass_class|
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blocks = [@init]
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@space.classes.values.each do |c|
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c.instance_methods.each do |f|
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nb = f.info.blocks
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raise "nil blocks " unless nb
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blocks += nb
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end
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end
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#puts "running #{pass_class}"
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blocks.each do |block|
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pass = eval pass_class
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raise "no such pass-class as #{pass_class}" unless pass
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pass.new.run(block)
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end
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end
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end
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# Passes may be added to by anyone who wants
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# This is intentionally quite flexible, though one sometimes has to watch the order of them
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# most ordering is achieved by ordering the requires and using add_pass
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# but more precise control is possible with the _after and _before versions
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def add_pass pass
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@passes << pass
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end
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def add_pass_after( pass , after)
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index = @passes.index(after)
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raise "No such pass (#{pass}) to add after: #{after}" unless index
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@passes.insert(index+1 , pass)
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end
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def add_pass_before( pass , after)
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index = @passes.index(after)
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raise "No such pass to add after: #{after}" unless index
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@passes.insert(index , pass)
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end
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def self.boot
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instance = self.instance
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# boot is a verb here. this is a somewhat tricky process which is in it's own file, boot.rb
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instance.boot_parfait!
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instance
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end
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def self.instance
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@instance ||= Machine.new
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end
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# for testing, make sure no old artefacts hang around
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#maybe should be moved to test dir
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def self.reboot
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@instance = nil
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self.boot
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end
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def compile_main bytes
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syntax = @parser.parse_with_debug(bytes)
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parts = Parser::Transform.new.apply(syntax)
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Compiler.compile( parts , @space.get_main )
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end
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end
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end
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require_relative "boot"
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