Improve to_string and x25crc

DFReader.py

@@ -127,45 +127,29 @@ def set_unit_ids(self, unit_ids):
     def set_mult_ids(self, mult_ids):
         '''set mult IDs string from FMTU'''
         self.mult_ids = mult_ids
-            
+
     def __str__(self):
         return ("DFFormat(%s,%s,%s,%s)" %
                 (self.type, self.name, self.format, self.columns))
 
 # Swiped into mavgen_python.py
 def to_string(s):
     '''desperate attempt to convert a string regardless of what garbage we get'''
-    try:
-        return s.decode("utf-8")
-    except Exception as e:
-        pass
-    try:
-        s2 = s.encode('utf-8', 'ignore')
-        x = u"%s" % s2
-        return s2
-    except Exception:
-        pass
-    # so it's a nasty one. Let's grab as many characters as we can
-    r = ''
-    while s != '':
-        try:
-            r2 = r + s[0]
-            s = s[1:]
-            r2 = r2.encode('ascii', 'ignore')
-            x = u"%s" % r2
-            r = r2
-        except Exception:
-            break
-    return r + '_XXX'
-
-def null_term(str):
+    if isinstance(s, str):
+        return s
+    if sys.version_info[0] == 2:
+        # In python2 we want to return unicode for passed in unicode
+        return s
+    return s.decode(errors="backslashreplace")
+
+def null_term(string):
     '''null terminate a string'''
-    if isinstance(str, bytes):
-        str = to_string(str)
-    idx = str.find("\0")
+    if isinstance(string, bytes):
+        string = to_string(string)
+    idx = string.find("\0")
     if idx != -1:
-        str = str[:idx]
-    return str
+        string = string[:idx]
+    return string
 
 
 class DFMessage(object):
@@ -1130,7 +1114,7 @@ def init_arrays(self, progress_callback=None):
             if mtype == "FMTU":
                 self.offset = ofs
                 self._parse_next()
-                
+
             ofs = self.data_map.find(b"\n", ofs)
             if ofs == -1:
                 break

generator/mavcrc.py

@@ -4,37 +4,38 @@
 Copyright Andrew Tridgell
 Released under GNU LGPL version 3 or later
 '''
+import sys
 from builtins import object
 
 
 class x25crc(object):
-    '''CRC-16/MCRF4XX - based on checksum.h from mavlink library'''
+    """CRC-16/MCRF4XX - based on checksum.h from mavlink library"""
+
     def __init__(self, buf=None):
-        self.crc = 0xffff
+        self.crc = 0xFFFF
         if buf is not None:
-            if isinstance(buf, str):
-                self.accumulate_str(buf)
-            else:
-                self.accumulate(buf)
+            self.accumulate(buf)
 
     def accumulate(self, buf):
-        '''add in some more bytes'''
+        """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 = buf.encode()
+
         accum = self.crc
         for b in buf:
-            tmp = b ^ (accum & 0xff)
-            tmp = (tmp ^ (tmp<<4)) & 0xFF
-            accum = (accum>>8) ^ (tmp<<8) ^ (tmp<<3) ^ (tmp>>4)
+            tmp = b ^ (accum & 0xFF)
+            tmp = (tmp ^ (tmp << 4)) & 0xFF
+            accum = (accum >> 8) ^ (tmp << 8) ^ (tmp << 3) ^ (tmp >> 4)
         self.crc = accum
 
     def accumulate_str(self, buf):
-        '''add in some more bytes'''
-        accum = self.crc
-        import array
-        bytes_array = array.array('B')
-        try:  # if buf is bytes
-            bytes_array.frombytes(buf)
-        except TypeError:  # if buf is str
-            bytes_array.frombytes(buf.encode())
-        except AttributeError:  # Python < 3.2
-            bytes_array.fromstring(buf)
-        self.accumulate(bytes_array)
+        """
+        Provided for backwards compatibility. accumulate now also works on strings.
+        """
+        return self.accumulate(buf)

mavutil.py

@@ -15,6 +15,9 @@
 import re
 from pymavlink import mavexpression
 
+# We want to re-export x25crc here
+from pymavlink.generator.mavcrc import x25crc as x25crc
+
 is_py3 = sys.version_info >= (3,0)
 supports_type_annotations = sys.version_info >= (3,6)
 
@@ -2281,27 +2284,6 @@ def mode_string_acm(mode_number):
         return mode_mapping_acm[mode_number]
     return "Mode(%u)" % mode_number
 
-class x25crc(object):
-    '''CRC-16/MCRF4XX - based on checksum.h from mavlink library'''
-    def __init__(self, buf=''):
-        self.crc = 0xffff
-        self.accumulate(buf)
-
-    def accumulate(self, buf):
-        '''add in some more bytes'''
-        byte_buf = array.array('B')
-        if isinstance(buf, array.array):
-            byte_buf.extend(buf)
-        else:
-            byte_buf.fromstring(buf)
-        accum = self.crc
-        for b in byte_buf:
-            tmp = b ^ (accum & 0xff)
-            tmp = (tmp ^ (tmp<<4)) & 0xFF
-            accum = (accum>>8) ^ (tmp<<8) ^ (tmp<<3) ^ (tmp>>4)
-            accum = accum & 0xFFFF
-        self.crc = accum
-
 class MavlinkSerialPort(object):
         '''an object that looks like a serial port, but
         transmits using mavlink SERIAL_CONTROL packets'''

tools/mavlogdump.py

@@ -155,28 +155,13 @@ def reduce_rate_msg(m, reduction_rate):
 
 # swiped from DFReader.py
 def to_string(s):
-    """desperate attempt to convert a string regardless of what garbage we get"""
-    try:
-        return s.decode("utf-8")
-    except Exception:
-        pass
-    try:
-        s2 = s.encode("utf-8", "ignore")
-        x = u"%s" % s2
-        return x
-    except Exception:
-        pass
-    # so it's a nasty one. Let's grab as many characters as we can
-    r = ""
-    try:
-        for c in s:
-            r2 = r + c
-            r2 = r2.encode("ascii", "ignore")
-            x = u"%s" % r2
-            r = r2
-    except Exception:
-        pass
-    return r + "_XXX"
+    '''desperate attempt to convert a string regardless of what garbage we get'''
+    if isinstance(s, str):
+        return s
+    if sys.version_info[0] == 2:
+        # In python2 we want to return unicode for passed in unicode
+        return s
+    return s.decode(errors="backslashreplace")
 
 def match_type(mtype, patterns):
     '''return True if mtype matches pattern'''
@@ -259,7 +244,7 @@ def match_type(mtype, patterns):
 
     if args.reduce_rate > 0 and reduce_rate_msg(m, args.reduce_rate):
         continue
-    
+
     if output is not None:
         if (isbin or islog) and m_type == "FMT":
             output.write(m.get_msgbuf())