def getResultingDataAddress(self, offset):
if len(self.segments) == 0:
return offset
else:
#check if segment descriptor exists
if len(self.segments) < self.DS:
raise CPUSegmentViolationException(SEGMENT_DATA, offset)
#check type of segment
if self.segments[self.DS].type != SEGMENT_DATA:
raise CPUSegmentViolationException(SEGMENT_DATA, offset)
#check boundaries of segment
if offset < self.segments[self.DS].start or offset > self.segments[
self.DS].limit:
raise CPUSegmentViolationException(SEGMENT_DATA, offset)
return offset
def setRegister(self, reg, value):
if reg < 0 or reg > 30:
raise CPUStateError(
"Can't access register smaller than 0 or bigger than 30")
if len(self.segments) == 0:
self.memory.writeWord(0x2000 + reg, value)
else:
#check if segment descriptor exists
if len(self.segments) < self.RS:
raise CPUSegmentViolationException(SEGMENT_REGISTER, reg)
#check type of segment
if self.segments[self.RS].type != SEGMENT_REGISTER:
raise CPUSegmentViolationException(SEGMENT_REGISTER, reg)
#write register to memory
self.memory.writeWord(self.segments[self.RS].start + reg, value)
def getResultingInstructionAddress(self):
#TODO: check if privLvl is not violated
if len(self.segments) == 0:
return self.IP
else:
#check if segment descriptor exists
if len(self.segments) < self.CS:
raise CPUSegmentViolationException(SEGMENT_CODE, self.IP)
#check type of segment
if self.segments[self.CS].type != SEGMENT_CODE:
raise CPUSegmentViolationException(SEGMENT_CODE, self.IP)
#check boundaries of segment
if self.IP < self.segments[
self.CS].start or self.IP > self.segments[self.CS].limit:
raise CPUSegmentViolationException(SEGMENT_CODE, self.IP)
return self.IP
def getResultingStackAddress(self):
if len(self.segments) == 0:
return self.getRegister(30)
else:
sp = self.getRegister(30)
#check if segment descriptor exists
if len(self.segments) < self.SS:
raise CPUSegmentViolationException(SEGMENT_STACK, sp)
#check type of segment
if self.segments[self.SS].type != SEGMENT_STACK:
raise CPUSegmentViolationException(SEGMENT_STACK, sp)
#check boundaries of segment
if sp < self.segments[self.SS].start or sp > self.segments[
self.SS].limit:
raise CPUSegmentViolationException(SEGMENT_STACK, sp)
return sp