46 lines
1.5 KiB
Ruby
46 lines
1.5 KiB
Ruby
|
|
module Asm
|
|
# Base class for anything that we can assemble
|
|
|
|
# Derived classes include instrucitons, blocks and data(strings)
|
|
|
|
# The commonality abstracted here is the length and position
|
|
# and the ability to assemble itself into the stream
|
|
|
|
# All code is position independant once assembled.
|
|
# But for jumps and calls two passes are neccessary.
|
|
# The first setting the position, the second assembling
|
|
class Code
|
|
|
|
# just sets position to nil, so we can sell that it has not been set
|
|
def initialize
|
|
@position = nil
|
|
end
|
|
|
|
# the position in the stream. Think of it as an address if you want. The difference is small.
|
|
# Especially since we produce _only_ position independant code
|
|
# in other words, during assembly the position _must_ be resolved into a pc relative address
|
|
# and not used as is
|
|
def position
|
|
throw "Not set" unless @address
|
|
@address
|
|
end
|
|
|
|
# The containing class (assembler/function) call this to tell the instruction/data where it is in the
|
|
# stream. During assembly the position is then used to calculate pc relative addresses.
|
|
def at address
|
|
@address = address
|
|
end
|
|
|
|
# length for this code in bytes
|
|
def length
|
|
throw "Not implemented #{self}"
|
|
end
|
|
|
|
# so currently the interface passes the io (usually string_io) in for the code to assemble itself.
|
|
# this may change as the writing is still done externally (or that will change)
|
|
def assemble(io)
|
|
throw "Not implemented #{self}"
|
|
end
|
|
end
|
|
end |