// meshes - массив или список UnityEngine.Mesh
var meshDataArray = Mesh.AllocateWritableMeshData(meshes);
for (var i = 0; i < meshes.Length; i++)
{
   var meshData = meshDataArray[i];
   meshData.SetVertexBufferParams(vertexCount, Vertex.Layout);
   meshData.SetIndexBufferParams(indexCount, IndexFormat.UInt32);

    var vertexArray = meshData.GetVertexData<Vertex>();
    var indexArray = meshData.GetIndexData<int>();
    // какая-то логика
}
Mesh.ApplyAndDisposeWritableMeshData(meshDataArray, meshes, MeshUpdateFlags.DontRecalculateBounds | MeshUpdateFlags.DontResetBoneBounds);

[StructLayout(LayoutKind.Explicit)]
[DebuggerDisplay("Position = {Position}, Normal = {Normal}")]
public readonly struct Vertex : IEquatable<Vertex>
{
   public static readonly VertexAttributeDescriptor[] Layout =
   {
      new(VertexAttribute.Position, VertexAttributeFormat.Float32, 3),
      new(VertexAttribute.Normal, VertexAttributeFormat.Float32, 3)
   };
        
   [FieldOffset(0)]
   public readonly float3 Position;
   [FieldOffset(12)]
   public readonly float3 Normal;
        
   public Vertex(float3 position, float3 normal)
   {
      Position = position;
      Normal = normal;
   }
}

var array = CollectionHelper.CreateNativeArray<int>(1000, /*какой-то аллокатор*/);

CollectionHelper.DisposeNativeArray(array, /*какой-то аллокатор*/);

public class SurfaceDataProcessor : BaseDataProcessor<SurfaceData>, ISurfaceDataProcessor
{
   protected sealed override void OnDataAdded(in Chunk chunk, ref SurfaceData data){}
   protected sealed override void OnDataRemoved(in Chunk chunk){}
}