Add SortedSetCount to IGarnetApi

[badrishc]

Discussed in #967

^{Originally posted by solanpaa January 28, 2025}
Hi,

I'm developing custom transactions for our use case. There I need to call, e.g., IGarnetApi.SortedSetCount. How do I set the input and read the output?

Minimum example of my issue

using Garnet.common;
using Garnet.server;
using Tsavorite.core;

namespace Garnet {

  public class MyTx : CustomTransactionProcedure
  {
        public override bool Prepare<TGarnetReadApi>(TGarnetReadApi api, ref CustomProcedureInput input) {
            int offset = 0;
            // Lock the key for exclusive access
            AddKey(GetNextArg(ref input, ref offset), LockType.Exclusive, true);
            return true;
        }

        public override void Main<TGarnetApi>(TGarnetApi api, ref CustomProcedureInput input, ref MemoryResult<byte> output)
        {
            int offset = 0;
            var key = GetNextArg(ref input, ref offset);
            var minScore = GetNextArg(ref input, ref offset);
            var maxScore = GetNextArg(ref input, ref offset);

            var keyBytes = key.ToArray();
           
            //
            // HELP: How to set zcountInput to correspond to 'minScore maxScore'?
            //
            ObjectInput zcountInput = new ObjectInput();
            GarnetObjectStoreOutput zcountOutput = new GarnetObjectStoreOutput();

            var status = api.SortedSetCount(keyBytes, ref zcountInput, ref zcountOutput);

            //
            // HELP: How to read count from zcountOutput?
            //
            int countOutput = 0; // <- ??
            var myCalculation = countOutput + 1;

            WriteSimpleString(ref output, myCalculation.ToString());

        }
  }
}

I tried looking up different ways ObjectInput and GarnetObjectStoreOutput are used within the codebase, but most uses seem to rely on internal-only functionalities. Would appreciate some pointers on how to use these in my own extensions