PAL Settings API aIndex argument

[jkcko]

Please clarify how the aIndex argument is used in the PAL settings.h API.

The comments state that the order of the items associated with a specific key does not need to be maintained when added or deleted, but it is not clear on any further requirements with regards to the the use of the index or storage of the items regarding the index.

If n items are added and stored in indexes 0 to n-1, and then item with index i where i < n-1 is deleted,

• Can item i remain empty such that a subsequent call to otPlatSettingsGet on index i returns OT_ERROR_NOT_FOUND?
• Or must the item at index i be filled in such that otPlatformSettingsGet returns OT_ERROR_NONE for indexes 0 to n-2 and otPlatformSettingsGet with index n-1 will return OT_ERROR_NOT_FOUND?

[abtink]

@jkcko,

Or must the item at index i be filled in such that otPlatformSettingsGet returns OT_ERROR_NONE for indexes 0 to n-2 and otPlatformSettingsGet with index n-1 will return OT_ERROR_NOT_FOUND?

This is the expected behavior.

The settings key are either single-value or list-based.

• otPlatSettingsGet() should allow iterating through all items in the list one by one by incrementing aIndex.
• OT_ERROR_NOT_FOUND indicates end of the list.
• The order of items in the list-based key can change after otPlatSettingsAdd() or otPlatSettingsDelete() calls.