Add py script to add timeout to bitstream

examples/add_autoboot_timeout.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+import argparse
+import sys
+
+parser = argparse.ArgumentParser(description="Add auto-boot timeout to bitstream")
+parser.add_argument("infile", type=str)
+parser.add_argument("outfile", type=str)
+parser.add_argument("--timeout", type=int, default=5)
+args = parser.parse_args()
+
+COMMENT_START = 0x00FF
+COMMENT_END = 0xFF00
+MAGIC_WORD = 0x4A6DE3AC
+BITSTREAM_SYNC_HEADER1 = 2123999870
+BITSTREAM_SYNC_HEADER2 = 2125109630
+ENDIANNESS = "little"
+
+
+def to_bytes(v, n=4):
+    return v.to_bytes(n, byteorder=ENDIANNESS, signed=False)
+
+
+def from_bytes(v):
+    return int.from_bytes(v, byteorder=ENDIANNESS)
+
+
+if args.timeout < 1 or args.timeout > 255:
+    sys.stderr.write("Pick a timeout between 1s and 255s")
+    sys.exit(1)
+
+with open(args.infile, "rb") as infile:
+    with open(args.outfile, "wb") as outfile:
+        first_word = from_bytes(infile.read(4))
+        if (
+            first_word != BITSTREAM_SYNC_HEADER1
+            and first_word != BITSTREAM_SYNC_HEADER2
+            and first_word & 0xFFFF != COMMENT_START
+        ):
+            sys.stderr.write("Unsupported file")
+            sys.exit(1)
+        outfile.write(to_bytes(COMMENT_START))
+        outfile.write(to_bytes(MAGIC_WORD))
+        outfile.write(to_bytes(args.timeout))
+        if first_word & 0xFFFF == COMMENT_START:  # there already is a comments section
+            outfile.write(to_bytes(0, n=2))  # make sure alignment is correct
+            outfile.write(to_bytes(first_word >> 16, n=2))
+        else:
+            outfile.write(to_bytes(COMMENT_END))
+        outfile.write(infile.read())