60 lines
1.9 KiB
Ruby
60 lines
1.9 KiB
Ruby
module Risc
|
|
# Little glue class to get the assembled binary from the Arm Instructions into
|
|
# the BinaryCode instances. Arm code originally uses io, but slightly modified
|
|
# really only uses write_unsigned_int_32 , which converts
|
|
# to an set_internal_word on the BinaryCode
|
|
#
|
|
# Machine instantiates and the writer reads from the arm Instructions
|
|
# and writes to the BinaryCode
|
|
class BinaryWriter
|
|
def initialize( code )
|
|
@code = code
|
|
end
|
|
|
|
# write into the given BinaryCode instance
|
|
# LinkException may be thrown, possibly several times
|
|
# So repeat until it works
|
|
def assemble( instruction )
|
|
ok = false
|
|
until(ok)
|
|
begin
|
|
assemble_all(instruction)
|
|
ok = true
|
|
rescue LinkException
|
|
end
|
|
end
|
|
end
|
|
|
|
# Go through and assemble all instructions.
|
|
# Assembly may cause LinkException, which is caught by caller
|
|
def assemble_all( instruction )
|
|
@index = 1
|
|
while(instruction)
|
|
instruction.assemble(self)
|
|
instruction = instruction.next
|
|
end
|
|
end
|
|
|
|
def write_unsigned_int_32( bin )
|
|
@code.set_word( @index , bin )
|
|
@index += 1
|
|
end
|
|
end
|
|
|
|
# A LinkException is raised when the arm code can't fit a constant into _one_
|
|
# instruction. This is kind of unavoidable with arm.
|
|
#
|
|
# Off course the problem could be fixed without the exception, but the exception
|
|
# means all subsequent Instructions, including labels/jump targets move.
|
|
# Thus changing jump instructions to those labels.
|
|
# So the whole method has to be reassembled and (at least) the instructions beyond
|
|
# repositioned. Ie a non-local problem, and so the Exception.
|
|
#
|
|
# Note: In the future i hope to have a more flexible system, possibly with position
|
|
# listeners and change events. Because positions chaning is normal, not exceptional.
|
|
#
|
|
class LinkException < Exception
|
|
end
|
|
|
|
end
|