fpga: Fix Xilinx bitfile parser for Python 3

The script was previously only Python 2 compatible.

Python 2 support is now removed, so we don't maintain backwards
compatibility with Python 2.

This also fixes all linter warnings.


Original-commit: 6046e1a812ba2065d6ae13b4c4afdce8abc99d4f

tools/scripts/xil_bitfile_parser.py

@@ -1,4 +1,9 @@
 #!/usr/bin/env python3
+"""
+Parser for Xilinx bitfiles.
+
+Reads metadata from Xilinx bitfile headers.
+"""
 
 import argparse
 import os
@@ -7,7 +12,8 @@ import struct
 import re
 
 # Parse command line options
-def get_options():
+def get_args():
+    """Run argparser"""
     parser = argparse.ArgumentParser(description='Parser for the Xilinx FPGA Bitfile')
     parser.add_argument("bitfile", help="Input bitfile path")
     parser.add_argument("--bin_out", help="Output bin file path")
@@ -20,60 +26,77 @@ def get_options():
         sys.exit(1)
     return args
 
-short = struct.Struct('>H')
-ulong = struct.Struct('>I')
-KEYNAMES = {'a':'design_name', 'b':'part_name', 'c':'date', 'd':'time'}
-
-# Parse bitfile
 def parse_bitfile(bitfile_bytes):
+    """
+    Parse bitfile
+    """
+    short = struct.Struct('>H')
+    ulong = struct.Struct('>I')
+    keynames = {'a': 'design_name', 'b': 'part_name', 'c': 'date', 'd': 'time'}
+
     header = dict()
     ptr = 0
     #Field 1
-    if short.unpack(bitfile_bytes[ptr:ptr+2])[0] == 9 and ulong.unpack(bitfile_bytes[ptr+2:ptr+6])[0] == 0x0ff00ff0:
+    if short.unpack(bitfile_bytes[ptr:ptr+2])[0] == 9 and \
+            ulong.unpack(bitfile_bytes[ptr+2:ptr+6])[0] == 0x0ff00ff0:
         #Headers
         ptr += short.unpack(bitfile_bytes[ptr:ptr+2])[0] + 2
         ptr += short.unpack(bitfile_bytes[ptr:ptr+2])[0] + 1
         #Fields a-d
-        for keynum in range(0, 4):
-            key = bitfile_bytes[ptr]; ptr += 1
-            val_len = short.unpack(bitfile_bytes[ptr:ptr+2])[0]; ptr += 2
-            val = bitfile_bytes[ptr:ptr+val_len]; ptr += val_len
-            header[KEYNAMES[key]] = str(val).rstrip('\0')
+        for _ in range(0, 4):
+            key = chr(bitfile_bytes[ptr])
+            ptr += 1
+            val_len = short.unpack(bitfile_bytes[ptr:ptr+2])[0]
+            ptr += 2
+            val = bitfile_bytes[ptr:ptr+val_len]
+            ptr += val_len
+            header[keynames[key]] = val.decode('ascii').rstrip('\0')
         #Field e
         ptr += 1
-        length = ulong.unpack(bitfile_bytes[ptr:ptr+4])[0]; ptr += 4
+        length = ulong.unpack(bitfile_bytes[ptr:ptr+4])[0]
+        ptr += 4
         header['bitstream_len'] = length
         header['header_len'] = ptr
         data = bitfile_bytes[ptr:ptr+length]
         return (header, data)
-    else:
-        raise Exception('Bitfile header validation failed!') 
+    raise Exception('Bitfile header validation failed!')
 
-# Flip 32-bit endianess
 def flip32(data):
-    sl = struct.Struct('<I')
-    sb = struct.Struct('>I')
-    b = memoryview(data)
-    d = bytearray(len(data))
+    """
+    Flip 32-bit endianness
+    """
+    le32_struct = struct.Struct('<I')
+    be32_struct = struct.Struct('>I')
+    data_flipped = bytearray(len(data))
     for offset in range(0, len(data), 4):
-         sb.pack_into(d, offset, sl.unpack_from(b, offset)[0])
-    return d
+        be32_struct.pack_into(
+            data_flipped,
+            offset,
+            le32_struct.unpack_from(memoryview(data), offset)[0])
+    return data_flipped
 
 def main():
-    args = get_options();
+    """GoGoGo"""
+    args = get_args()
     with open(args.bitfile, 'rb') as bit_file:
         # Parse bytes into a header map and data buffer
         (header, data) = parse_bitfile(bit_file.read())
         # Print bitfile info
         if args.info:
-            m = re.search('(.+);UserID=(.+);COMPRESS=(.+);Version=(.+)', header['design_name'])
-            if m:
-                print('Design Name: ' + m.group(1))
-                print('User ID: ' + m.group(2))
-                print('Compression: ' + m.group(3))
-                print('Vivado Version: ' + m.group(4))
-            else:
-                print('Design Name: ' + header['design_name'])
+            keynames = {
+                'COMPRESS': 'Compression: ',
+                'UserID': 'User ID: ',
+                'Version': 'Vivado Version: '}
+            name_fields = header['design_name'].split(';')
+            for field in name_fields:
+                mobj = re.search('(.+)=(.+)', field)
+                if mobj:
+                    if mobj.group(1) in keynames:
+                        print(keynames[mobj.group(1)] + mobj.group(2))
+                    else:
+                        print(mobj.group(1) + ': ' + mobj.group(2))
+                else:
+                    print('Design Name: ' + field)
             print('Part Name: ' + header['part_name'])
             print('Datestamp: ' + header['date'] + ' ' + header['time'])
             print('Bitstream Size: ' + str(header['bitstream_len']))