add bitinfo script

python/bitinfo.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""
+Read header of Xilinx .bit files.
+
+./bitinfo.py some.bit
+"""
+
+import sys
+import struct
+
+for fname in sys.argv[1:]:
+    info = {}
+
+    with open(fname, 'rb') as F:
+        if F.read(13)!=b'\0\x09\x0f\xf0\x0f\xf0\x0f\xf0\x0f\xf0\0\0\1':
+            print("Not a bit file")
+            sys.exit(1)
+
+        while True:
+            head = F.read(1)
+            if len(head)==0:
+                break
+
+            if head[0] in (0x61, 0x62, 0x63, 0x64):
+                size, = struct.unpack('!H', F.read(2))
+                body = F.read(size)
+                assert len(body)==size
+
+                info[head[0]] = body.decode('utf-8').rstrip('\0')
+
+            elif head[0] in (0x65,):
+                size, = struct.unpack('!I', F.read(4))
+                F.seek(size, 1) # skip
+                info[head[0]] = size
+
+            else:
+                raise RuntimeError("Unknown %s at %s"%(head[0], F.tell()))
+
+    print(fname)
+    print("  Description:", info.pop(0x61, '?'))
+    print("  Part:", info.pop(0x62, '?'))
+    print("  Build date:", info.pop(0x63, '?'), info.pop(0x64, '?'))
+    print("  Bit stream length:", info.pop(0x65, 0))
+
+    if info:
+        print("  Extra:", info)