From 6cd06758c23ca8fcff76bd210da7b0cca5da46b7 Mon Sep 17 00:00:00 2001
From: Chris Torrence <5461379+ct6502@users.noreply.github.com>
Date: Wed, 21 Feb 2024 09:13:55 -0700
Subject: [PATCH] Add support for disks with arbitrary number of tracks; add
 sample disk images

---
 .gitignore  |   1 +
 35track.dsk | Bin 0 -> 143360 bytes
 35track.po  | Bin 0 -> 143360 bytes
 40track.dsk | Bin 0 -> 163840 bytes
 40track.po  | Bin 0 -> 163840 bytes
 README.md   |  10 +++++---
 dsk2po.py   |  68 ++++++++++++++++++++++++++++------------------------
 po2dsk.py   |  11 +++++++--
 8 files changed, 54 insertions(+), 36 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 35track.dsk
 create mode 100644 35track.po
 create mode 100644 40track.dsk
 create mode 100644 40track.po

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ed097e1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+__pycache__/dsk2po.cpython-311.pyc
diff --git a/35track.dsk b/35track.dsk
new file mode 100644
index 0000000000000000000000000000000000000000..2b87e0d2cf7b2b71b7acdbc313f35bbe6ac92dae
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diff --git a/40track.dsk b/40track.dsk
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diff --git a/40track.po b/40track.po
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diff --git a/README.md b/README.md
index 90541f3..b898e17 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
-# dsk2po
-Python script to convert Apple II/III .DSK (DO) images to ProDOS-ordered images
+# dsk2po and po2dsk
+Python scripts to convert Apple II/III .DSK (DO) images to ProDOS-ordered images
+and vice versa.
 
 This is nothing very exciting, it just maps sectors in .dsk (DOS-order, .do) files
 into those of a .po (ProDOS-order) file.  Most Apple II emulators can handle both,
@@ -11,7 +12,10 @@ Usage is just (assuming you've done `chmod 755 dsk2po.py`, else precede with pyt
     ./dsk2po.py image.dsk
 
 This will create image.dsk.po alongside it.  Pretty much no checking is done.
-It just goes through 35 tracks and converts them, then ends.
+It just goes through all the tracks and converts them, then ends.
+
+Both scripts will handle an arbitrary number of tracks, but will print a
+warning if the number of tracks is not 35.
 
 This can be used as an action for find, like so:
 
diff --git a/dsk2po.py b/dsk2po.py
index 3c638b8..546d620 100755
--- a/dsk2po.py
+++ b/dsk2po.py
@@ -1,33 +1,39 @@
 #!/usr/bin/env python3
 # unscramble dsk into po
 # Paul Hagstrom, Dec 2015
-import sys, getopt, re
+import sys, getopt, re, os
 def main(argv=None):
-	print("dsk2po - convert dsk files to po files")
+  print("dsk2po - convert dsk files to po files")
 
-	try:
-		opts, args = getopt.getopt(sys.argv[1:], '')
-	except getopt.GetoptError as err:
-		print(str(err))
-		usage()
-		return 1
-	try:
-		dskfilename = args[0]
-	except:
-		print('You need to provide the name of a DSK file to begin.')
-		return 1
+  try:
+    opts, args = getopt.getopt(sys.argv[1:], '')
+  except getopt.GetoptError as err:
+    print(str(err))
+    usage()
+    return 1
+  try:
+    dskfilename = args[0]
+  except:
+    print('You need to provide the name of a DSK file to begin.')
+    return 1
 
-	potracks = []
-	with open(dskfilename, mode="rb") as dskfile:
-		for track in range(35):
-			trackbuffer = dskfile.read(4096)
-			potracks.append(dsk2po(trackbuffer))
-	pofilename = re.sub('\.dsk$', '', dskfilename, flags=re.IGNORECASE) + ".po"
-	print('Writing po image to {}'.format(pofilename))
-	with open(pofilename, mode="wb") as pofile:
-		for potrack in potracks:
-			pofile.write(potrack)
-	return 0
+  # Handle arbitrary number of tracks (normally should be 35)
+  fileSize = os.path.getsize(dskfilename)
+  ntracks = fileSize // 4096
+  if ntracks != 35:
+    print("Warning: DSK file has non-standard {} tracks".format(ntracks))
+
+  potracks = []
+  with open(dskfilename, mode="rb") as dskfile:
+    for track in range(ntracks):
+      trackbuffer = dskfile.read(4096)
+      potracks.append(dsk2po(trackbuffer))
+  pofilename = re.sub('\.dsk$', '', dskfilename, flags=re.IGNORECASE) + ".po"
+  print('Writing po image to {}'.format(pofilename))
+  with open(pofilename, mode="wb") as pofile:
+    for potrack in potracks:
+      pofile.write(potrack)
+  return 0
 
 # From Beneath Apple ProDOS, table 3.1
 # block 000 physical 0, 2 DOS 0, E page 0, 1
@@ -45,12 +51,12 @@ def main(argv=None):
 block_map = [0, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 15]
 
 def dsk2po(trackbuffer):
-	potrack = bytearray()
-	for chunk in range(16):
-		chunk_start = 256*block_map[chunk]
-		chunk_end = chunk_start + 256
-		potrack.extend(trackbuffer[chunk_start:chunk_end])
-	return potrack
+  potrack = bytearray()
+  for chunk in range(16):
+    chunk_start = 256*block_map[chunk]
+    chunk_end = chunk_start + 256
+    potrack.extend(trackbuffer[chunk_start:chunk_end])
+  return potrack
 
 if __name__ == "__main__":
-	sys.exit(main())
+  sys.exit(main())
diff --git a/po2dsk.py b/po2dsk.py
index fe49b59..8f6060f 100755
--- a/po2dsk.py
+++ b/po2dsk.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # scramble po back into dsk
 # Chris Torrence, Oct 2020
-import sys, getopt, re
+import sys, getopt, re, os
 from dsk2po import dsk2po
 def main(argv=None):
   print("po2dsk - convert po files to dsk files")
@@ -18,10 +18,17 @@ def main(argv=None):
     print('You need to provide the name of a PO file to begin.')
     return 1
 
+  # Handle arbitrary number of tracks (normally should be 35)
+  fileSize = os.path.getsize(filenameIn)
+  ntracks = fileSize // 4096
+  if ntracks != 35:
+    print("Warning: PO file has non-standard {} tracks".format(ntracks))
+
   tracks = []
+
   # Note that the same algorithm can be used to convert in either direction
   with open(filenameIn, mode="rb") as fileIn:
-    for track in range(35):
+    for track in range(ntracks):
       trackbuffer = fileIn.read(4096)
       tracks.append(dsk2po(trackbuffer))
   dskfilename = re.sub('\.po$', '', filenameIn, flags=re.IGNORECASE) + ".dsk"