Jared Miller
3140a4d617
ZStackBottom already had stack and local_vars for uniform treatment, but was missing return_addr. Adding it removes 5 type: ignore suppressions and fixes all ty possibly-missing-attribute warnings.
215 lines
7.3 KiB
Python
215 lines
7.3 KiB
Python
#
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# A class which manages both (1) the general purpose stack ("data
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# stack") used by the story code to store temporary data, and (2) the
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# interpreter-private stack of routines ("call stack") and their local
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# variables.
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#
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# For the license of this file, please consult the LICENSE file in the
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# root directory of this distribution.
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#
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from .zlogging import log
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class ZStackError(Exception):
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"General exception for stack or routine-related errors"
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pass
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class ZStackUnsupportedVersion(ZStackError):
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"Unsupported version of Z-story file."
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pass
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class ZStackNoRoutine(ZStackError):
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"No routine is being executed."
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pass
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class ZStackNoSuchVariable(ZStackError):
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"Trying to access non-existent local variable."
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pass
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class ZStackPopError(ZStackError):
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"Nothing to pop from stack!"
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pass
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# Helper class used by ZStackManager; a 'routine' object which
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# includes its own private stack of data.
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class ZRoutine:
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def __init__(
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self, start_addr, return_addr, zmem, args, local_vars=None, stack=None
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):
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"""Initialize a routine object beginning at START_ADDR in ZMEM,
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with initial argument values in list ARGS. If LOCAL_VARS is None,
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then parse them from START_ADDR."""
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self.start_addr = start_addr
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self.return_addr = return_addr
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self.program_counter = 0 # used when execution interrupted
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self.arg_count = len(args) # track number of args passed
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if stack is None:
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self.stack = []
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else:
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self.stack = stack[:]
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if local_vars is not None:
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self.local_vars = local_vars[:]
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else:
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num_local_vars = zmem[self.start_addr]
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if not (0 <= num_local_vars <= 15):
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log(f"num local vars is {num_local_vars}")
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raise ZStackError
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self.start_addr += 1
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# Initialize the local vars in the ZRoutine's dictionary. This is
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# only needed on machines v1 through v4. In v5 and v8 machines, all
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# local variables are preinitialized to zero.
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self.local_vars = [0 for _ in range(15)]
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if 1 <= zmem.version <= 4:
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for i in range(num_local_vars):
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self.local_vars[i] = zmem.read_word(self.start_addr)
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self.start_addr += 2
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elif zmem.version not in (5, 8):
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raise ZStackUnsupportedVersion
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# Place call arguments into local vars, if available
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for i in range(0, len(args)):
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self.local_vars[i] = args[i]
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def pretty_print(self):
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"Display a ZRoutine nicely, for debugging purposes."
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log(f"ZRoutine: start address: {self.start_addr}")
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log(f"ZRoutine: return value address: {self.return_addr}")
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log(f"ZRoutine: program counter: {self.program_counter}")
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log(f"ZRoutine: local variables: {self.local_vars}")
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class ZStackBottom:
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"""Sentinel object at the bottom of the call stack.
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Includes stack and local_vars attributes so code that walks the call
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stack can treat all frames uniformly without special-case checks for
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the bottom sentinel.
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"""
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def __init__(self):
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self.program_counter = 0 # used as a cache only
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self.return_addr = None
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self.stack = []
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self.local_vars = [0 for _ in range(15)]
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class ZStackManager:
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def __init__(self, zmem):
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self._memory = zmem
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self._stackbottom = ZStackBottom()
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self._call_stack = [self._stackbottom]
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def get_local_variable(self, varnum):
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"""Return value of local variable VARNUM from currently-running
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routine. VARNUM must be a value between 0 and 15, and must
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exist."""
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if self._call_stack[-1] == self._stackbottom:
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raise ZStackNoRoutine
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if not 0 <= varnum <= 15:
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raise ZStackNoSuchVariable
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current_routine = self._call_stack[-1]
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return current_routine.local_vars[varnum]
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def set_local_variable(self, varnum, value):
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"""Set value of local variable VARNUM to VALUE in
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currently-running routine. VARNUM must be a value between 0 and
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15, and must exist."""
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if self._call_stack[1] == self._stackbottom:
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raise ZStackNoRoutine
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if not 0 <= varnum <= 15:
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raise ZStackNoSuchVariable
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current_routine = self._call_stack[-1]
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current_routine.local_vars[varnum] = value
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def push_stack(self, value):
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"Push VALUE onto the top of the current routine's data stack."
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current_routine = self._call_stack[-1]
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current_routine.stack.append(value)
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def pop_stack(self):
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"Remove and return value from the top of the data stack."
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current_routine = self._call_stack[-1]
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if not current_routine.stack:
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frame_idx = len(self._call_stack) - 1
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ra = getattr(current_routine, "return_addr", "N/A")
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pc = getattr(current_routine, "program_counter", 0)
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raise ZStackPopError(f"frame {frame_idx}, return_addr={ra}, pc=0x{pc:06x}")
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return current_routine.stack.pop()
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def get_stack_frame_index(self):
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"Return current stack frame number. For use by 'catch' opcode."
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return len(self._call_stack) - 1
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# Used by quetzal save-file parser to reconstruct stack-frames.
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def push_routine(self, routine):
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"""Blindly push a ZRoutine object to the call stack.
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WARNING: do not use this unless you know what you're doing; you
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probably want the more full-featured start_routine() belowe
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instead."""
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self._call_stack.append(routine)
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# ZPU should call this whenever it decides to call a new routine.
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def start_routine(self, routine_addr, return_addr, program_counter, args):
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"""Save the state of the currenly running routine (by examining
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the current value of the PROGRAM_COUNTER), and prepare for
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execution of a new routine at ROUTINE_ADDR with list of initial
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arguments ARGS."""
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new_routine = ZRoutine(routine_addr, return_addr, self._memory, args)
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current_routine = self._call_stack[-1]
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current_routine.program_counter = program_counter
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self._call_stack.append(new_routine)
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return new_routine.start_addr
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# ZPU should call this whenever it decides to return from current
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# routine.
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def finish_routine(self, return_value):
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"""Toss the currently running routine from the call stack, and
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toss any leftover values pushed to the data stack by said routine.
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Return the previous routine's program counter address, so that
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execution can resume where from it left off."""
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exiting_routine = self._call_stack.pop()
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current_routine = self._call_stack[-1]
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# Depending on many things, return stuff.
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if exiting_routine.return_addr is not None:
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if exiting_routine.return_addr == 0:
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# Push to stack
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self.push_stack(return_value)
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elif 0 < exiting_routine.return_addr < 0x10:
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# Store in local var
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self.set_local_variable(exiting_routine.return_addr - 1, return_value)
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else:
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# Store in global var
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self._memory.write_global(exiting_routine.return_addr, return_value)
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return current_routine.program_counter
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