Implement --verify option

Now Alpaca ISP can verify that the flash was successfully written.  It
does a full comparison of the data, which is perhaps a bit heavy-handed
given that we're mostly worried about random bit errors.  Maybe I'll
eventually implement a CRC32-based verify routine for faster but less
perfect verification.

alpaca_isp/__init__.py

         lpc.prepare_write()
         lpc.erase()
 
-    # Write the files to flash
+    # Load the files
     ih = intelhex.IntelHex()
     for f in args.file:
         ih.fromfile(f, format="hex")
 
+    # Write the files to flash
     try:
         lpc.flash_hex(ih, verbose=True)
     except ISPError as e:
         if e.args[0] == ReturnCode.CODE_READ_PROTECTION_ENABLED:
             print("Error: code read protection is enabled")
+            print("Unable to flash, exiting")
         sys.exit(2)
 
-    # TODO: Verify that the flash has been written correctly if we've been
-    # asked to
+    # Verify that the flash has been written correctly if we've been asked to
+    if args.verify:
+        try:
+            lpc.verify(ih, verbose=True)
+        except ISPError as e:
+            if e.args[0] == ReturnCode.CODE_READ_PROTECTION_ENABLED:
+                print("Error: code read protection is enabled")
+                print("Unalbe to verify, continuing")
 
     # Start the program if we haven't been asked not to
     if not args.no_start:
+        print("Starting program")
         lpc.go()
 
     lpc.close()

alpaca_isp/lpc.py

             self.copy_ram_to_flash(ss[sector][0], self._chip.ram_base,
                     len(secdat))
 
+    def verify(self, ihex, verbose=False):
+        """Verify that the data in an IntelHex object is stored in flash"""
+        # Get the sectors we're verifying
+        sectors_used = self._chip.sectors_used(ihex.segments())
+
+        # Verify segments
+        ss = self._chip.sector_segments
+        for sector in sectors_used:
+            if verbose:
+                print("Verifying sector {}... ".format(sector), end="")
+            # Get the data we're verifying
+            secdat = ihex.tobinstr(start=ss[sector][0], end=ss[sector][1]-1)
+
+            # Read data from flash
+            try:
+                flash = self.read_memory(ss[sector][0],
+                        self._chip.sectors[sector])
+            except ISPError as e:
+                if e.args[0] == ReturnCode.CODE_READ_PROTECTION_ENABLED:
+                    print()
+                raise
+
+            # Verify the sector
+            if secdat != flash:
+                print("failed!")
+            else:
+                print()
+
 
 class LPC8xx(LPC):
     """Interface for LPC8xx in-system programming"""