Extdata: Difference between revisions

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 == Quota File ==
-The inner data of <code>Quota.dat</code> is 0x48 bytes with the following format. The file seems to limit the extdata total size.
+The inner data of <code>Quota.dat</code> is 0x48 bytes with the following format. The file applies limits to the file system, similar to quotas for other file systems.
 {| class="wikitable" border="1"
@@ Line 47: / Line 47: @@
 | 0x04
 | 4
-| Magic 0x30000
+| Version, always 0x30000
 |-
 | 0x08
 | 4
-| 0x1000, block size
+| Block size. Always 0x1000.
 |-
 | 0x0C
 | 4
-| Always 126. Probably device directory capacity. See the [[#Device Directory Capacity]] more information.
+| Maximum number of physical files in each physical directory. Always 126. See [[#Device Directory Capacity]] for more information.
 |-
 | 0x10
 | 4
-| Always 0?
+| padding
 |-
 | 0x14
+| 8
+| Block count (capacity)
+|-
+| 0x1C
+| 8
+| Number of remaining blocks
+|-
+| 0x24
 | 4
-| Max number of blocks
+| Current pending operation
+{| class="wikitable" border="1"
+! Value !! Description
 |-
-| 0x18
+| 0 || No pending operation.
-| 4
+|-
-| Always 0?
+| 1 || Physical file deletion is pending
 |-
-| 0x1C
+| 2 || Physical file resize is pending (redundant, see below note)
-| 4
-| Free blocks remained
 |-
-| 0x20
+| 3 || Physical subdirectory creation is pending
-| 4
-| Always 0?
 |-
-| 0x24
+| 4 || Physical subdirectory deletion is pending
-| 4
+|}
-| Always 0?
 |-
 | 0x28
-| 4
+| 8
-| Free blocks remained + (blocks occupied by the recently mounted file, specified by the ID below (0 if recently deleted))
+| Number of available blocks (from offset 0x1C) at the time the above operation was queued (if any).
-|-
-| 0x2C
-| 4
-| Always 0?
 |-
 | 0x30
-| 4
+| 8
-| ID of most recently mounted file. Same as the one in [[Inner_FAT#Filesystem Header]]
+| File ID that is related to the above operation info. Same as the one in [[Inner_FAT#Filesystem Header]]
-|-
-| 0x34
-| 4
-| Always 0?
 |-
 | 0x38
-| 4
+| 8
-| Always 0?
+| File size of the above mentioned file. For resize, this is interpreted as the old file size.
-|-
-| 0x3C
-| 4
-| Always 0?
 |-
 | 0x40
-| 4
+| 8
-| Size in bytes of most recently mounted file (device file size). 0 if recently deleted
+| For resize operations, the new file size to apply for the above mentioned file.
 |-
-| 0x44
-| 4
-| Always 0?
 |}
+The quota is implemented as follows:
+* During initial Extdata creation with [[FS:CreateExtSaveData]], the input size limit is divided by the block size (0x1000). This becomes the block count (capacity).
+* Each physical subdirectory (not to be confused with the inner virtual directories in the EXSV filesystem) counts one block towards the block quota.
+** Every 126 files, a new physical subdirectory is created.
+** This includes the initial physical subdirectory (00000000).
+* Each physical subfile (= full DIFF container for a virtual file) counts its file size (rounded up to the quota block size) in blocks towards the block quota.
+** This includes all initial physical subfiles, namely `icon` and the root EXSV filesystem file containing the [[Inner_FAT#Filesystem Header]].
+** The physical subfile size is taken as the number of blocks corresponding to the physical subfile size rounded up to the block size as specified in the Quota.dat.
+* Quota.dat itself is given one block.
+Note: Extdata files do not support resizing after their initial creation, because each file is a separate, fixed-size DIFF container. The resize operation is therefore nonfunctional.
 == Device Directory Capacity ==