fixbaserom.py: Add support to v64 format and improve performance (#629)

* Add byte swap for v64 files

Signed-off-by: angie <angheloalf95@gmail.com>

* Reduce `len` function calls

Signed-off-by: angie <angheloalf95@gmail.com>

* Optimze a bit the byte-swapped v64 format

Signed-off-by: angie <angheloalf95@gmail.com>

* Strip the overdump before doing the byte-swap

The previous way wasted time by byte-swapping data that would be discarded anyway.

Signed-off-by: angie <angheloalf95@gmail.com>

* Swap twice the bytes per cycle to improve performance

Signed-off-by: angie <angheloalf95@gmail.com>

* Read and write 16 bytes at a time and specify explicit endianness

Reading more bytes per cycle allow to speed up the swapping proccess

Signed-off-by: angie <angheloalf95@gmail.com>

* Add v64 compatibility in the Readme

Signed-off-by: angie <angheloalf95@gmail.com>

* Read whole file as little endian and write it as big endian without the loop

Signed-off-by: angie <angheloalf95@gmail.com>

README.md

@@ -94,7 +94,7 @@ git clone https://github.com/zeldaret/oot.git
 #### 4. Prepare a base ROM
 
 Copy over your copy of the Master Quest (Debug) ROM inside the root of this new project directory.
-Rename the file to "baserom_original.z64" or "baserom_original.n64", depending on the original extension.
+Rename the file to "baserom_original.z64", "baserom_original.n64" or "baserom_original.v64", depending on the original extension.
 
 #### 5. Setup the ROM and build process
 

fixbaserom.py

@@ -22,44 +22,54 @@ if path.exists("baserom_original.z64"):
     romFileName = "baserom_original.z64"
 elif path.exists("baserom_original.n64"):
     romFileName = "baserom_original.n64"
+elif path.exists("baserom_original.v64"):
+    romFileName = "baserom_original.v64"
+else:
+    print("Error: Could not find baserom_original.z64/baserom_original.n64/baserom_original.v64.")
+    sys.exit(1)
 
 # Read in the original ROM
-if romFileName != "":
+print("File '" + romFileName + "' found.")
-    print("File '" + romFileName + "' found.")
+with open(romFileName, mode="rb") as file:
-    with open(romFileName, mode="rb") as file:
+    fileContent = bytearray(file.read())
-        fileContent = bytearray(file.read())
 
-        # Check if ROM needs to be byte swapped
-        if fileContent[0] == 0x40:
-            # Byte Swap ROM
-            # TODO: This is pretty slow at the moment. Look into optimizing it later...
-            print("ROM needs to be byte swapped...")
-            i = 0
-            while i < len(fileContent):
-                tmp = struct.unpack_from("BBBB", fileContent, i)
-                struct.pack_into("BBBB", fileContent, i + 0, tmp[3], tmp[2], tmp[1], tmp[0])
-                i += 4
-
-                perc = float(i) / float(len(fileContent))
-
-                if i % (1024 * 1024 * 4) == 0:
-                    print(str(perc * 100) + "%")
-        
-            print("Byte swapping done.")
-else:
-    print("Error: Could not find baserom_original.z64/baserom_original.n64.")
-    sys.exit(1)
-    
 # Strip the overdump
 print("Stripping overdump...")
-strippedContent = list(fileContent[0:0x3600000])
+fileContent = fileContent[0:0x3600000]
+
+fileContentLen = len(fileContent)
+
+# Check if ROM needs to be byte/word swapped
+# Little-endian
+if fileContent[0] == 0x40:
+    # Word Swap ROM
+    print("ROM needs to be word swapped...")
+    words = str(int(fileContentLen/4))
+    little_byte_format = "<" + words + "I"
+    big_byte_format = ">" + words + "I"
+    tmp = struct.unpack_from(little_byte_format, fileContent, 0)
+    struct.pack_into(big_byte_format, fileContent, 0, *tmp)
+
+    print("Word swapping done.")
+
+# Byte-swapped
+elif fileContent[0] == 0x37:
+    # Byte Swap ROM
+    print("ROM needs to be byte swapped...")
+    halfwords = str(int(fileContentLen/2))
+    little_byte_format = "<" + halfwords + "H"
+    big_byte_format = ">" + halfwords + "H"
+    tmp = struct.unpack_from(little_byte_format, fileContent, 0)
+    struct.pack_into(big_byte_format, fileContent, 0, *tmp)
+
+    print("Byte swapping done.")
 
 # Patch the header
 print("Patching header...")
-strippedContent[0x3E] = 0x50
+fileContent[0x3E] = 0x50
 
 # Check to see if the ROM is a "vanilla" Debug ROM
-str_hash = get_str_hash(bytearray(strippedContent))
+str_hash = get_str_hash(bytearray(fileContent))
 if str_hash != "f0b7f35375f9cc8ca1b2d59d78e35405":
     print("Error: Expected a hash of f0b7f35375f9cc8ca1b2d59d78e35405 but got " + str_hash + ". " +
           "The baserom has probably been tampered, find a new one")
@@ -68,6 +78,6 @@ if str_hash != "f0b7f35375f9cc8ca1b2d59d78e35405":
 # Write out our new ROM
 print("Writing new ROM 'baserom.z64'.")
 with open("baserom.z64", mode="wb") as file:
-    file.write(bytes(strippedContent))
+    file.write(bytes(fileContent))
 
-print("Done!")
+print("Done!")