Move file handling into ChkSum class.

gcksum.py

@@ -5,21 +5,11 @@ from grmn import ChkSum
 import sys
 
 FILE = sys.argv[1]
-BLOCKSIZE = 4 * 1024
-
-print("Reading {} ".format(FILE), end="")
 
 csum = ChkSum()
-
-with open(FILE, "rb") as f:
-    while True:
-        block = f.read(BLOCKSIZE)
-        csum.add(block)
-        print(".", end="", flush=True)
-        if len(block) < BLOCKSIZE:
-            print(" done.")
-            break
-    f.close()
+print("Reading {} ...".format(FILE), end="", flush=True)
+csum.add_from_file(FILE, print_progress=True)
+print(" done.")
 
 print("Sum of all bytes: {:02x}".format(csum.get_sum()))
 print("Last byte: {:02x}".format(csum.get_last_byte()))

grmn/chksum.py

@@ -15,6 +15,17 @@ class ChkSum:
         self.last_byte = data[-1]
         self.chksum += self.last_byte
         self.chksum &= 0xff
+    
+    def add_from_file(self, filename: str, print_progress: bool = False, blocksize: int=16384):
+        with open(filename, "rb") as f:
+            while True:
+                block = f.read(blocksize)
+                self.add(block)
+                if print_progress:
+                    print(".", end="", flush=True)
+                if len(block) < blocksize:
+                    break
+            f.close()
 
     def get(self):
         remainder = ( 0x100 - self.chksum ) & 0xff