Nintendo 64 - Nintendo Switch Online: Difference between revisions

Line 147:

= SuspendPoint =

The SuspendPoint is stored in a mostly standard cpio archive~~. The magic is~~ little-endian octal ~~070707. Normally the~~ file data is ~~used raw, however when u8 cpio_entry_header+0x4~~ (~~c_ino~~) ~~is 0x1 and~~ +~~0x5 is 0x0,~~ the file data is zlib compressed. The cpio parser code calculates a checksum over each file (decompressed data when compression is enabled) by XORing each u16 in the file, then comparing it with ~~u16 cpio_entry_header+0x8 (c_uid)~~. The result is stored as a flag in the output cpio file entry structure. This checksum is only set for SuspendPoints, not RomFs data - none of the cpio parser callers currently validate the checksum flag.

The SuspendPoint is stored in a mostly standard cpio archive with a modified cpio entry header:

{| class="wikitable" border="1"

|-

! Offset

! Size

! Description

|-

| 0x0 || 0x2 || Magic (070707 in little-endian octal)

|-

| 0x2 || 0x2 || Dev (0x3E16 or 0x0000 if trailer block)

|-

| 0x4 || 0x2 || Flags (0x1 means file data is zlib compressed)

|-

| 0x6 || 0x2 || Mode (unused)

|-

| 0x8 || 0x2 || Checksum

|-

| 0xA || 0x2 || DecompFileSize1 (lower half of decompressed file size)

|-

| 0xC || 0x2 || DecompFileSize2 (higher half of decompressed file size)

|-

| 0xE || 0x2 || Rdev (unused)

|-

| 0x10 || 0x2 || Mtime1 (unused)

|-

| 0x12 || 0x2 || Mtime2 (unused)

|-

| 0x14 || 0x2 || NameSize (size of file name)

|-

| 0x16 || 0x2 || FileSize1 (lower half of file size)

|-

| 0x18 || 0x2 || FileSize2 (higher half of file size)

|-

| 0x1A || NameSize || FileName

|-

| 0x1A + NameSize || FileSize || FileData

|}

Normally the file data is used raw, but it can also be zlib compressed if '''flags''' is 0x1. The cpio parser code calculates a checksum over each file (decompressed data when compression is enabled) by XORing each u16 in the file, then comparing it with '''checksum'''. The result is stored as a flag in the output cpio file entry structure. This checksum is only set for SuspendPoints, not RomFs data - none of the cpio parser callers currently validate the checksum flag.

This archive is stored in [[#SaveData]], and is also transferred over the network with online-play-friends when the user loads a suspend-point in the GUI. This is also done automatically when a network session is created, for emu-sync-state. Emu-sync-state only used with session-creation, after that the only way to trigger suspend-point usage is via the suspend-menu GUI.

@@ Line 147: / Line 147: @@
 = SuspendPoint =
-The SuspendPoint is stored in a mostly standard cpio archive. The magic is little-endian octal 070707. Normally the file data is used raw, however when u8 cpio_entry_header+0x4 (c_ino) is 0x1 and +0x5 is 0x0, the file data is zlib compressed. The cpio parser code calculates a checksum over each file (decompressed data when compression is enabled) by XORing each u16 in the file, then comparing it with u16 cpio_entry_header+0x8 (c_uid). The result is stored as a flag in the output cpio file entry structure. This checksum is only set for SuspendPoints, not RomFs data - none of the cpio parser callers currently validate the checksum flag.
+The SuspendPoint is stored in a mostly standard cpio archive with a modified cpio entry header:
+{| class="wikitable" border="1"
+|-
+! Offset
+! Size
+! Description
+|-
+| 0x0 || 0x2 || Magic (070707 in little-endian octal)
+|-
+| 0x2 || 0x2 || Dev (0x3E16 or 0x0000 if trailer block)
+|-
+| 0x4 || 0x2 || Flags (0x1 means file data is zlib compressed)
+|-
+| 0x6 || 0x2 || Mode (unused)
+|-
+| 0x8 || 0x2 || Checksum
+|-
+| 0xA || 0x2 || DecompFileSize1 (lower half of decompressed file size)
+|-
+| 0xC || 0x2 || DecompFileSize2 (higher half of decompressed file size)
+|-
+| 0xE || 0x2 || Rdev (unused)
+|-
+| 0x10 || 0x2 || Mtime1 (unused)
+|-
+| 0x12 || 0x2 || Mtime2 (unused)
+|-
+| 0x14 || 0x2 || NameSize (size of file name)
+|-
+| 0x16 || 0x2 || FileSize1 (lower half of file size)
+|-
+| 0x18 || 0x2 || FileSize2 (higher half of file size)
+|-
+| 0x1A || NameSize || FileName
+|-
+| 0x1A + NameSize || FileSize || FileData
+|}
+Normally the file data is used raw, but it can also be zlib compressed if '''flags''' is 0x1. The cpio parser code calculates a checksum over each file (decompressed data when compression is enabled) by XORing each u16 in the file, then comparing it with '''checksum'''. The result is stored as a flag in the output cpio file entry structure. This checksum is only set for SuspendPoints, not RomFs data - none of the cpio parser callers currently validate the checksum flag.
 This archive is stored in [[#SaveData]], and is also transferred over the network with online-play-friends when the user loads a suspend-point in the GUI. This is also done automatically when a network session is created, for emu-sync-state. Emu-sync-state only used with session-creation, after that the only way to trigger suspend-point usage is via the suspend-menu GUI.