1 files changed, 49 insertions, 0 deletions
diff --git a/linearizeDisk.py b/linearizeDisk.py
new file mode 100755
index 0000000..55f4b06
--- /dev/null
+++ b/linearizeDisk.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+
+"""
+For some reason blocks in the bitsavers images are not in linear order, but
+shuffled. Not sure why and if other disks are affected as well, but this script
+reorders them.
+"""
+
+import os, logging
+from itertools import chain
+
+def linearBlocks (fd):
+    fd.seek (0, os.SEEK_END)
+    size = fd.tell ()
+    logging.debug ('File size is {} bytes'.format (size))
+
+    blockSize = 512
+    blocksPerChunk = 15
+    chunkSize = blockSize*blocksPerChunk
+    chunks = size//chunkSize
+    skip = 1
+    if size%chunkSize != 0:
+        logging.warning ('File size {} is not multiple of chunk size {}'.format (size, chunkSize))
+
+    # first even then odd chunks
+    for j in chain (range (0, chunks, 2), range (1, chunks, 2)):
+        pos = j*chunkSize
+        logging.debug ('Seeking to {} for chunk {} and reading {} blocks @ {} bytes'.format (pos, j, blocksPerChunk, blockSize))
+        fd.seek (pos, os.SEEK_SET)
+        for i in range (blocksPerChunk):
+            yield fd.read (blockSize)
+
+if __name__ == '__main__':
+    import argparse, sys
+    
+    parser = argparse.ArgumentParser(description='Reorder EUMEL archive disk’s blocks.')
+    parser.add_argument ('-v', '--verbose', help='Enable debugging messages', action='store_true')
+    parser.add_argument ('input', help='Input file')
+    parser.add_argument ('output', help='Out file')
+    args = parser.parse_args ()
+    if args.verbose:
+        logging.basicConfig (level=logging.DEBUG)
+    else:
+        logging.basicConfig (level=logging.WARNING)
+
+    with open (args.input, 'rb') as infd, open (args.output, 'wb') as outfd:
+        for b in linearBlocks (infd):
+            outfd.write (b)
+