Fix bugs found running Zork 1 through hybrid interpreter
Spec fixes: implement op_test (bitwise AND branch), add missing branch to op_get_child, handle call-to-address-0 as no-op in op_call/_call. I/O fixes: correct keyboard API (keyboard_input.read_line), non-TTY fallbacks in trivialzui, stdout flush for immediate output. Graceful handling of unmapped ZSCII characters. Add instruction trace buffer for debugging.
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8d749fbb7e
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311a67e80a
GPG key ID:
22B5C6D66A38B06C
4 changed files with 75 additions and 14 deletions
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@ -115,6 +115,7 @@ class TrivialScreen(zscreen.ZScreen):
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for char in string:
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newline_printed = False
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sys.stdout.write(char)
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sys.stdout.flush()
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if char == "\n":
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newline_printed = True
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@ -292,6 +293,11 @@ def _unix_read_char():
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import tty
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fd = sys.stdin.fileno()
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# Check if stdin is a TTY - if not, use simple read
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if not sys.stdin.isatty():
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return sys.stdin.read(1)
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old_settings = termios.tcgetattr(fd)
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try:
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tty.setraw(sys.stdin.fileno())
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@ -333,6 +339,14 @@ def _read_line(original_text=None, terminating_characters=None):
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assert isinstance(original_text, str)
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assert isinstance(terminating_characters, str)
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# If stdin is not a TTY, use simple line reading
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if not sys.stdin.isatty():
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line = sys.stdin.readline()
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if not line: # EOF
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raise EOFError("End of input")
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# Strip newline but keep the content
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return line.rstrip("\n\r")
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chars_entered = len(original_text)
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sys.stdout.write(original_text)
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string = original_text
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@ -8,6 +8,7 @@
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import random
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import time
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from collections import deque
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from . import bitfield, zopdecoder, zscreen
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from .zlogging import log, log_disasm
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@ -53,6 +54,7 @@ class ZCpu:
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self._streammanager = zstreammanager
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self._ui = zui
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self._lexer = zlexer
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self._trace = deque(maxlen=20)
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def _get_handler(self, opcode_class, opcode_number):
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try:
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@ -60,6 +62,8 @@ class ZCpu:
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except IndexError:
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opcode_decl = None
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if not opcode_decl:
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cls, num = opcode_class, opcode_number
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print(f"DEBUG: Illegal opcode class={cls} num={num}")
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raise ZCpuIllegalInstruction
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# If the opcode declaration is a sequence, we have extra
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@ -80,6 +84,8 @@ class ZCpu:
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elif opcode_decl[1] <= self._memory.version:
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opcode_func = opcode_decl[0]
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else:
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cls, num = opcode_class, opcode_number
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print(f"DEBUG: Illegal opcode class={cls} num={num}")
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raise ZCpuIllegalInstruction
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# The following is a hack, based on our policy of only
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@ -143,6 +149,11 @@ class ZCpu:
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"""Set up a function call to the given routine address,
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passing the given arguments. If store_return_value is True,
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the routine's return value will be stored."""
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# Calling address 0 is a no-op that returns false (0).
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if routine_address == 0:
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if store_return_value:
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self._write_result(0)
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return
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addr = self._memory.packed_address(routine_address)
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if store_return_value:
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return_value = self._opdecoder.get_store_address()
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@ -168,12 +179,34 @@ class ZCpu:
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log(f"Jump to offset {branch_offset:+d}")
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self._opdecoder.program_counter += branch_offset - 2
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def _dump_trace(self):
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"""Print the last N instructions for debugging."""
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print("\n=== INSTRUCTION TRACE (last 20) ===")
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for entry in self._trace:
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print(entry)
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print("===================================\n")
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def step(self):
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"""Execute a single instruction. Returns True if execution should continue."""
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current_pc = self._opdecoder.program_counter
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log(f"Reading next opcode at address {current_pc:x}")
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(opcode_class, opcode_number, operands) = self._opdecoder.get_next_instruction()
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# Record raw byte at this PC for trace
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cls_str = zopdecoder.OPCODE_STRINGS.get(opcode_class, f"?{opcode_class}")
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trace_entry = f" {current_pc:06x} {cls_str}:{opcode_number:02x}"
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try:
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implemented, func = self._get_handler(opcode_class, opcode_number)
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except ZCpuIllegalInstruction:
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trace_entry += f" ILLEGAL (raw byte: {self._memory[current_pc]:02x})"
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self._trace.append(trace_entry)
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self._dump_trace()
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raise
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trace_entry += f" {func.__name__}({', '.join(str(x) for x in operands)})"
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self._trace.append(trace_entry)
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log_disasm(
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current_pc,
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zopdecoder.OPCODE_STRINGS[opcode_class],
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@ -256,9 +289,9 @@ class ZCpu:
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parent = self._objects.get_parent(obj1)
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self._branch(parent == obj2)
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def op_test(self, *args):
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"""TODO: Write docstring here."""
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raise ZCpuNotImplemented
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def op_test(self, bitmap, flags):
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"""Test if all bits in flags are set in bitmap, branch if true."""
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self._branch((bitmap & flags) == flags)
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def op_or(self, a, b):
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"""Bitwise OR between the two arguments."""
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@ -386,8 +419,10 @@ class ZCpu:
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self._branch(sibling != 0)
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def op_get_child(self, object_num):
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"""Get and store the first child of the given object."""
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self._write_result(self._objects.get_child(object_num))
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"""Get first child of object, store it, branch if nonzero."""
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child = self._objects.get_child(object_num)
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self._write_result(child)
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self._branch(child != 0)
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def op_get_parent(self, object_num):
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"""Get and store the parent of the given object."""
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@ -574,6 +609,10 @@ class ZCpu:
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# call in v1-3
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def op_call(self, routine_addr, *args):
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"""Call the routine r1, passing it any of r2, r3, r4 if defined."""
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# Calling address 0 is a no-op that returns false (0).
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if routine_addr == 0:
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self._write_result(0)
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return
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addr = self._memory.packed_address(routine_addr)
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return_addr = self._opdecoder.get_store_address()
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current_addr = self._opdecoder.program_counter
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@ -614,7 +653,7 @@ class ZCpu:
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self.op_show_status()
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# Read input from keyboard
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text = self._ui.keyboard.readline()
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text = self._ui.keyboard_input.read_line()
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text = text.lower().strip("\n\r")
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# Store in text buffer
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@ -442,7 +442,14 @@ class ZsciiTranslator:
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try:
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return self._output_table[index]
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except KeyError:
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raise IndexError("No such ZSCII character") from None
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# Handle undefined ZSCII characters
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# 0-31 (except 0, 10): control characters, return empty string
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# 128-154, 252-254: undefined, return placeholder
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# 155-251: extended characters, should have Unicode table but don't
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if index < 32:
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return ""
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# For undefined or unmapped characters, return a placeholder
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return "?"
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def utoz(self, char):
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"""Translate the given Unicode code into the corresponding
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@ -85,7 +85,8 @@ class MockUI:
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def __init__(self):
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self.screen = Mock()
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self.screen.write = Mock()
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self.keyboard = Mock()
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self.keyboard_input = Mock()
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self.keyboard_input.read_line = Mock()
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class ZMachineOpcodeTests(TestCase):
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@ -548,7 +549,7 @@ class ZMachineComplexOpcodeTests(TestCase):
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self.memory[text_buffer_addr] = 20 # max length
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# Mock keyboard input
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self.ui.keyboard.readline = Mock(return_value="hello world\n")
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self.ui.keyboard_input.read_line = Mock(return_value="hello world\n")
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# Call sread with text buffer only (no parse buffer)
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self.cpu.op_sread(text_buffer_addr, 0)
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@ -566,7 +567,7 @@ class ZMachineComplexOpcodeTests(TestCase):
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text_buffer_addr = 0x1000
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self.memory[text_buffer_addr] = 5 # max length of 5
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self.ui.keyboard.readline = Mock(return_value="hello world\n")
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self.ui.keyboard_input.read_line = Mock(return_value="hello world\n")
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self.cpu.op_sread(text_buffer_addr, 0)
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@ -581,7 +582,7 @@ class ZMachineComplexOpcodeTests(TestCase):
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text_buffer_addr = 0x1000
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self.memory[text_buffer_addr] = 20
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self.ui.keyboard.readline = Mock(return_value="HELLO World\n")
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self.ui.keyboard_input.read_line = Mock(return_value="HELLO World\n")
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self.cpu.op_sread(text_buffer_addr, 0)
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@ -594,7 +595,7 @@ class ZMachineComplexOpcodeTests(TestCase):
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text_buffer_addr = 0x1000
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self.memory[text_buffer_addr] = 20
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self.ui.keyboard.readline = Mock(return_value="test\r\n")
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self.ui.keyboard_input.read_line = Mock(return_value="test\r\n")
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self.cpu.op_sread(text_buffer_addr, 0)
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@ -607,7 +608,7 @@ class ZMachineComplexOpcodeTests(TestCase):
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"""Test sread calls op_show_status for V3."""
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text_buffer_addr = 0x1000
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self.memory[text_buffer_addr] = 20
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self.ui.keyboard.readline = Mock(return_value="test\n")
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self.ui.keyboard_input.read_line = Mock(return_value="test\n")
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# Track if show_status was called
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call_count = [0]
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