Function CMMetadataCreateKeyFromIdentifier 

pub unsafe extern "C-unwind" fn CMMetadataCreateKeyFromIdentifier(
    allocator: Option<&CFAllocator>,
    identifier: &CFString,
    key_out: NonNull<*const CFType>,
) -> i32

Available on crate feature CMMetadata only.

Creates a copy of the key encoded in the identifier as a CFType.

The returned CFType is based on the keyspace encoded in the identifier.

For OSType keyspaces, the key will be returned as a CFNumber, where a big endian interpretation of its kCFNumberSInt32Type value represents the four bytes of the key’s numeric value.

For the keyspaces kCMMetadataKeySpace_QuickTimeMetadata and kCMMetadataKeySpace_Icy, the key will be returned as a CFString.

All other keyspaces will have the function return the key as a CFData.

Safety

key_out must be a valid pointer.