From e3b2bc9839dbb4b880d6fdcefe7187d2528a23f7 Mon Sep 17 00:00:00 2001
From: n-hutton <nathan.cameron.hutton@gmail.com>
Date: Thu, 20 Feb 2025 14:39:31 +0000
Subject: [PATCH] strip date time files

---
 fpga/Makefile                       |  2 +-
 fpga/strip_date_time_from_binary.py | 52 +++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 fpga/strip_date_time_from_binary.py

diff --git a/fpga/Makefile b/fpga/Makefile
index 963fd1e28..dd9849a19 100644
--- a/fpga/Makefile
+++ b/fpga/Makefile
@@ -188,7 +188,7 @@ work:
 	$(Q)$(RM) $@ $*.drc $*.rbt
 	$(info [=] BITGEN $@)
 	$(Q)$(XILINX_TOOLS_PREFIX)bitgen $(VERBOSITY) -w $* $@
-	echo "FFFFFFFFFFFFFFFFFFFFFF" | dd of=fpga_pm3_hf.bit bs=1 seek=48 conv=notrunc
+	#python3 ../strip_date_time_from_binary.py $@ || true
 	$(Q)$(CP) $@ ..
 
 # Build all targets
diff --git a/fpga/strip_date_time_from_binary.py b/fpga/strip_date_time_from_binary.py
new file mode 100644
index 000000000..12e34c9dd
--- /dev/null
+++ b/fpga/strip_date_time_from_binary.py
@@ -0,0 +1,52 @@
+import sys
+
+# File to take a .bit file generated by xilinx webpack ISE
+# and replace the date and time embedded within with 'F'.
+# The header of the bitfile is seperated by ascii markers
+# 'a', 'b', 'c', 'd' etc.
+# see fpga_compress.c for comparison
+
+def parse_and_split_file(filename):
+    split_chars = ['a', 'b', 'c', 'd']  # Characters to split on
+    extracted_data = [] # for debug
+
+    print("Overwriting date and time in bitfile {}".format(filename))
+
+    with open(filename, 'rb') as f:  # Read as binary to handle non-text files
+        data = f.read(100)  # Read first 100 bytes which should contain all information
+
+    decoded_data = list(data.decode(errors='ignore'))
+
+    for i in range(len(decoded_data) - 3):
+        # subsequent two bytes after marker are null and the length
+        next_byte   = ord(decoded_data[i+1])
+        data_length = ord(decoded_data[i+2])
+
+        if decoded_data[i] == split_chars[0] and next_byte == 0x0:
+            start = i+3
+            extracted_data.append(''.join(decoded_data[start:start+data_length]))
+
+            # time, date
+            if split_chars[0] == 'c' or split_chars[0] == 'd':
+                decoded_data[start:start+data_length] = 'F' * data_length
+
+            split_chars.pop(0)
+
+            if not split_chars:
+                break
+
+    print("Extracted data from bitfile: {}".format(extracted_data))
+    decoded_data = ''.join(decoded_data).encode()
+
+    with open(filename, 'r+b') as f:  # Write back modified bytes
+        f.seek(0)
+        f.write(decoded_data.ljust(100, b' '))
+    print("writing complete")
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage: python script.py <filename>")
+        sys.exit(1)
+
+    filename = sys.argv[1]
+    parse_and_split_file(filename)