Combined Ptr.py and Ptp.py

pymlac/PtrPtp.py

@@ -0,0 +1,235 @@
+#!/usr/bin/python
+
+"""
+Emulate the imlac Paper Tape Reader/Punch (PTR/PTP).
+
+We take some pains to closely emulate the *real* device, even
+including misuse, such as no tape mounted.  This means we must tell
+the PTR/PTP object how many CPU cycles have passed (tick()).
+"""
+
+import struct
+
+from Globals import *
+
+
+class PtrPtp(object):
+
+    # number of chars per second we want
+    PtrCharsPerSecond = 300
+    PtpCharsPerSecond = 30
+
+    # duty cycle for PTR is 30% ready and 70% not ready
+    PtrReadyCycles = int((CYCLES_PER_SECOND / PtrCharsPerSecond) / 0.7) / 25
+    PtrNotReadyCycles = int((CYCLES_PER_SECOND / PtrCharsPerSecond) / 0.3) / 25
+    PtpNotReadyCycles = int(CYCLES_PER_SECOND / PtpCharsPerSecond)
+
+    # no tape in reader, return 0377 (all holes see light)
+    PtrEOF = 0377
+
+    # module-level state variables
+    device_use = None
+    device_motor_on = False
+    device_open_file = None
+    device_filename = None
+    device_cycle_count = 0
+    device_ready = False
+
+    ptr_at_eof = True
+    ptr_value = PtrEOF
+
+    # status values
+    InUsePTR = 'PTR'
+    InUsePTP = 'PTP'
+
+
+    def __init__(self):
+        """Initialize the papertape device."""
+
+        self.reset()
+
+    def reset(self):
+        """Reset device to a known state."""
+
+        # general device
+        self.device_use = None
+        self.device_motor_on = False
+        self.device_open_file = None
+        self.device_filename = None
+        self.device_open_file = None
+        self.device_filename = None
+        self.device_ready = False
+
+        # reader-specific
+        self.ptr_at_eof = True
+        self.ptr_value = self.PtrEOF
+
+    def ready(self):
+        """Test if device is ready."""
+
+        return self.device_ready
+
+    ###############
+    # Interface routines for reader
+    ###############
+
+    def ptr_mount(self, fname):
+        """Mount papertape file on the reader device."""
+
+        if self.device_use == self.InUsePTP:
+            raise RuntimeError("ptr_mount: Can't mount PTR file, being used as PTP")
+
+        self.device_use = self.InUsePTR
+        self.device_motor_on = False
+        self.device_filename = fname
+        self.device_open_file = open(self.device_filename, 'rb')
+        self.device_ready = False
+        self.device_cycle_count = self.PtrNotReadyCycles
+        self.ptr_at_eof = False
+        self.ptr_value = None
+
+    def ptr_dismount(self):
+        """Dismount a papertape file."""
+
+        if self.device_use == self.InUsePTP:
+            raise RuntimeError("ptr_dismount: Can't dismount PTR file, being used as PTP")
+
+        self.device_use = None
+        self.device_motor_on = False
+        self.device_ready = False
+        if self.device_filename:
+            self.device_open_file.close()
+            self.device_open_file = None
+        self.device_filename = None
+        self.ptr_at_eof = True
+        self.ptr_value = self.PtrEOF
+
+    def start(self):
+        """Turn papertape reader motor on."""
+
+        if self.device_use == self.InUsePTP:
+            raise RuntimeError("start: Can't start PTR motor, being used as PTP")
+
+        self.device_use = self.InUsePTR
+        self.device_motor_on = True
+        self.device_ready = False
+        self.device_cycle_count = self.PtrReadyCycles
+
+    def stop(self):
+        """Stop reader motor."""
+
+        if self.device_use == self.InUsePTP:
+            raise RuntimeError("stop: Can't stop PTR motor, being used as PTP")
+
+        self.device_motor_on = False
+        self.device_ready = False
+        self.device_cycle_count = self.PtrReadyCycles
+
+    def read(self):
+        """Read papertape value."""
+
+        if self.device_use == self.InUsePTP:
+            raise RuntimeError("ptr_read: Can't read PTR, being used as PTP")
+
+        return self.ptr_value
+
+    def ptr_eof(self):
+        """Return reader EOF status."""
+
+        if self.device_use == self.InUsePTP:
+            raise RuntimeError("ptr_eof: Can't read PTR status, being used as PTP")
+
+        return self.ptr_at_eof
+
+    def ptr_tick(self, cycles):
+        """Called to push PTR state along.
+
+        cycles  number of cycles passed since last tick
+        """
+
+        if self.device_use != self.InUsePTR:
+            return
+
+        # if end of tape or motor off, do nothing, state remains unchanged
+        if self.ptr_at_eof or not self.device_motor_on:
+            return
+
+        self.device_cycle_count -= cycles
+
+        if self.device_cycle_count <= 0:
+            if self.device_ready:
+                self.device_ready = False
+                self.device_cycle_count += self.PtrNotReadyCycles
+            else:
+                self.device_ready = True
+                self.device_cycle_count += self.PtrReadyCycles
+                self.ptr_value = self.device_open_file.read(1)
+                if len(self.ptr_value) < 1:
+                    # EOF on input file, pretend end of tape
+                    self.ptr_at_eof = True
+                    self.ptr_value = self.PtrEOF
+                else:
+                    self.ptr_value = ord(self.ptr_value)
+
+    ###############
+    # Interface routines for punch
+    ###############
+
+    def ptp_mount(self, fname):
+        """Mount papertape file on the punch device."""
+
+        # check usage of the device
+        if self.device_use == self.InUsePTR:
+            raise RuntimeError("ptp_mount: Can't mount PTP file, being used as PTR")
+
+        self.device_use = self.InUsePTP
+        self.device_motor_on = False
+        self.device_ready = False
+        self.device_cycle_count = self.PtrNotReadyCycles
+        self.ptp_filename = fname
+        self.device_open_file = open(self.ptp_filename, 'wb')
+        self.ptp_at_eof = False
+        self.ptp_value = None
+
+    def ptp_dismount(self):
+        """Dismount a papertape punch file."""
+
+        if self.device_use == self.InUsePTR:
+            raise RuntimeError("ptp_dismount: Can't dismount PTP file, being used as PTR")
+
+        self.device_motor_on = False
+        self.device_ready = False
+        if self.ptp_filename:
+            self.device_open_file.close()
+            self.device_open_file = None
+        self.ptp_filename = None
+        self.ptp_at_eof = True
+        self.ptp_value = self.PtrEOF
+
+    def punch(self, value):
+        """Write byte to papertape file.
+
+        value  8 bit value to punch
+        """
+
+        if self.device_use == self.InUsePTR:
+            raise RuntimeError("punch: Can't punch PTP file, being used as PTR")
+
+        self.device_ready = False
+        self.device_cycle_count = self.PtpNotReadyCycles
+        self.device_open_file.write(struct.pack('1B', value))
+
+    def ptp_tick(self, cycles):
+        """Called to push PTP state along.
+
+        cycles  number of cycles passed since last tick
+        """
+
+        if self.device_use != self.InUsePTP:
+            return
+
+        self.device_cycle_count -= cycles
+        if self.device_cycle_count <= 0:
+            self.device_ready = True
+            self.device_cycle_count += self.PtrNotReadyCycles
+