use fastcrc if available

generator/mavcrc.py

@@ -7,8 +7,13 @@
 import sys
 from builtins import object
 
+try:
+    import fastcrc
+    mcrf4xx = fastcrc.crc16.mcrf4xx
+except Exception:
+    mcrf4xx = None
 
-class x25crc(object):
+class x25crc_slow(object):
     """CRC-16/MCRF4XX - based on checksum.h from mavlink library"""
 
     def __init__(self, buf=None):
@@ -39,3 +44,57 @@ def accumulate_str(self, buf):
         Provided for backwards compatibility. accumulate now also works on strings.
         """
         return self.accumulate(buf)
+
+class x25crc_fast(object):
+    """CRC-16/MCRF4XX - based on checksum.h from mavlink library"""
+    def __init__(self, buf=None):
+        self.crc = 0xFFFF
+        if buf is not None:
+            self.accumulate(buf)
+
+    def accumulate(self, buf):
+        """add in some more bytes (it also accepts strings)"""
+        if sys.version_info[0] == 2:
+            if type(buf) is str:
+                buf = bytearray(buf)
+            elif type(buf).__name__ == 'unicode':
+                # we can't use the identifier unicode in python3
+                buf = bytearray(buf.encode())
+        elif type(buf) is str:
+            buf = bytes(buf.encode())
+        elif type(buf) is list:
+            buf = bytes(buf)
+        self.crc = mcrf4xx(buf, self.crc)
+
+    def accumulate_str(self, buf):
+        """
+        Provided for backwards compatibility. accumulate now also works on strings.
+        """
+        return self.accumulate(buf)
+
+if mcrf4xx is not None:
+    x25crc = x25crc_fast
+else:
+    x25crc = x25crc_slow
+
+if __name__ == "__main__":
+    import random, time
+
+    for i in range(100):
+        nbytes = random.randint(1000,5000)
+        b = random.randbytes(nbytes)
+
+        t1 = time.time()
+        slow = x25crc_slow()
+        t2 = time.time()
+        slow_t = t2 - t1
+
+        t1 = time.time()
+        c = x25crc()
+        t2 = time.time()
+        fast_t = t2 - t1
+
+        slow.accumulate(b)
+        c.accumulate(b)
+        assert slow.crc == c.crc
+        print("Speedup %.2f" % (slow_t/fast_t))

requirements.txt

@@ -2,7 +2,8 @@ lxml>=3.6.0
 future>=0.15.2
 wheel>=0.37.1
 setuptools>=42
+fastcrc
 
 # dev dependencies:
 pytest<=7.4.4
-syrupy; python_version>='3.6'
+syrupy; python_version>='3.6'