InMemoryKacke - ArrayIndexOutOfBoundsException on put

[caseymorris61]

Describe the bug My app crashed due to an array indexing exception when I was trying to store a value in an in-memory cache

java.lang.ArrayIndexOutOfBoundsException: length=7; index=-1
at com.mayakapps.kache.collection.MutableChain.resizeStorage$kache(Chain.kt:100)
at com.mayakapps.kache.collection.MutableChainedScatterMap.resizeStorage(MutableChainedScatterMap.kt:89)
at com.mayakapps.kache.collection.MutableScatterMap.adjustStorage(ScatterMap.kt:1314)
at com.mayakapps.kache.collection.MutableScatterMap.findInsertIndex$kache(ScatterMap.kt:1254)
at com.mayakapps.kache.collection.MutableScatterMap.put(ScatterMap.kt:991)
at com.mayakapps.kache.InMemoryKache.put(InMemoryKache.kt:233)

To Reproduce Steps to reproduce the behavior: Occurred when doing a put on an existing key. The onEntryRemoved listener correctly fired but the put failed

Expected behavior The app should not crash and the put should succeed.

System (please complete the following information):

• Multiplatform library running on Android

Additional context My cache creation when it crashes looks like:

val pageCache = InMemoryKache<String, CacheableResponse>(maxSize = cacheSize) {
        strategy = KacheStrategy.LRU
        expireAfterWriteDuration = CACHE_EXPIRATION_TIME_MS.milliseconds
        onEntryRemoved = { evicted, key, oldValue, newValue ->
            println("CACHE: Page Entry Removed - Evicted: $evicted")
        }
    }

Note: If I change the Strategy to FIFO, I do not get a crash

[caseymorris61]

Looking through the code is how I discovered it would work with a FIFO instead of an LRU. The issue seems to be related to resizing the MutableChainedScatterMap.insertionChain. When doing the resizing, the insertionChain.tail is -1 for some reason, and MutableChain.resizeStorage() only checks oldHead index before accessing.

I think the resizeStorage() should include more checks, but am curious if there is an issue elsewhere causing the tail of the insertion chain to remain at -1

[caseymorris61]

So I did more digging and there are 2 issues around the resizing:

1. the oldTail is not saved before the resizing in MutableChain.resizeStorage(), so it is reset to -1, and then when we try to access it, we get an index out of bounds error.
2. When updating the extras (i.e. the time marks of the mutable timed chain), it is done out of sequece, after the index has been advanced, which was causing other issues.

I will submit an MR to fix

[bitfisher]

Hi @MSDarwish2000, we've also ran into this! A bugfix release would be very helpful!

It seems to happen also when using FIFO instead of LRU.

[MSDarwish2000]

Sorry for the delay in releasing the bugfix release. I have just released it.