FitFile._read_struct does not allow endian in fmt

Like before 5d8bb3a
And microoptimization for string concat

fitparse/base.py

@@ -65,11 +65,7 @@ def _read(self, size):
         return data
 
     def _read_struct(self, fmt, endian='<', data=None, always_tuple=False):
-        if fmt.startswith('<') or fmt.startswith('>'):
-            # fmt contains endian
-            fmt_with_endian = fmt
-        else:
-            fmt_with_endian = "%s%s" % (endian, fmt)
+        fmt_with_endian = endian + fmt
         size = struct.calcsize(fmt_with_endian)
         if size <= 0:
             raise FitParseError("Invalid struct format: %s" % fmt_with_endian)
@@ -247,10 +243,7 @@ def _parse_raw_values_from_data_message(self, def_mesg):
             base_type = field_def.base_type
             is_byte = base_type.name == 'byte'
             # Struct to read n base types (field def size / base type size)
-            struct_fmt = '%d%s' % (
-                field_def.size / base_type.size,
-                base_type.fmt,
-            )
+            struct_fmt = str(int(field_def.size / base_type.size)) + base_type.fmt
 
             # Extract the raw value, ask for a tuple if it's a byte type
             raw_value = self._read_struct(

fitparse/records.py

@@ -341,7 +341,7 @@ class Crc(object):
         0xA001, 0x6C00, 0x7800, 0xB401, 0x5000, 0x9C01, 0x8801, 0x4400,
     )
 
-    FMT = '<H'
+    FMT = 'H'
 
     def __init__(self, value=0, byte_arr=None):
         self.value = value

tests/test.py

@@ -64,8 +64,8 @@ def generate_fitfile(data=None, endian='<'):
 
     # Prototcol version 1.0, profile version 1.52
     header = pack('<2BHI4s', 14, 16, 152, len(fit_data), b'.FIT')
-    file_data = header + pack(Crc.FMT, Crc.calculate(header)) + fit_data
-    return file_data + pack(Crc.FMT, Crc.calculate(file_data))
+    file_data = header + pack('<' + Crc.FMT, Crc.calculate(header)) + fit_data
+    return file_data + pack('<' + Crc.FMT, Crc.calculate(file_data))
 
 
 def secs_to_dt(secs):