Antlr4.Runtime.Atn.MergeCache.Put C# (CSharp) Method

        public void Put(PredictionContext a, PredictionContext b, PredictionContext value)
        {
            Dictionary<PredictionContext, PredictionContext> first;
            if (!data.TryGetValue(a, out first))
            {
                first = new Dictionary<PredictionContext, PredictionContext>();
                data[a] = first;
            }
            first[b] = value;
        }

        public static PredictionContext MergeArrays(
            ArrayPredictionContext a,
            ArrayPredictionContext b,
            bool rootIsWildcard,
            MergeCache mergeCache)
        {
            if (mergeCache != null)
            {
                PredictionContext previous = mergeCache.Get(a, b);
                if (previous != null)
                {
                    return(previous);
                }
                previous = mergeCache.Get(b, a);
                if (previous != null)
                {
                    return(previous);
                }
            }

            // merge sorted payloads a + b => M
            int i = 0;             // walks a
            int j = 0;             // walks b
            int k = 0;             // walks target M array

            int[] mergedReturnStates =
                new int[a.returnStates.Length + b.returnStates.Length];
            PredictionContext[] mergedParents =
                new PredictionContext[a.returnStates.Length + b.returnStates.Length];
            // walk and merge to yield mergedParents, mergedReturnStates
            while (i < a.returnStates.Length && j < b.returnStates.Length)
            {
                PredictionContext a_parent = a.parents[i];
                PredictionContext b_parent = b.parents[j];
                if (a.returnStates[i] == b.returnStates[j])
                {
                    // same payload (stack tops are equal), must yield merged singleton
                    int payload = a.returnStates[i];
                    // $+$ = $
                    bool both_dollar = payload == EMPTY_RETURN_STATE &&
                                       a_parent == null && b_parent == null;
                    bool ax_ax = (a_parent != null && b_parent != null) &&
                                 a_parent.Equals(b_parent);                                        // ax+ax -> ax
                    if (both_dollar || ax_ax)
                    {
                        mergedParents[k]      = a_parent;                    // choose left
                        mergedReturnStates[k] = payload;
                    }
                    else               // ax+ay -> a'[x,y]
                    {
                        PredictionContext mergedParent =
                            Merge(a_parent, b_parent, rootIsWildcard, mergeCache);
                        mergedParents[k]      = mergedParent;
                        mergedReturnStates[k] = payload;
                    }
                    i++;                     // hop over left one as usual
                    j++;                     // but also skip one in right side since we merge
                }
                else if (a.returnStates[i] < b.returnStates[j])
                {                 // copy a[i] to M
                    mergedParents[k]      = a_parent;
                    mergedReturnStates[k] = a.returnStates[i];
                    i++;
                }
                else                   // b > a, copy b[j] to M
                {
                    mergedParents[k]      = b_parent;
                    mergedReturnStates[k] = b.returnStates[j];
                    j++;
                }
                k++;
            }

            // copy over any payloads remaining in either array
            if (i < a.returnStates.Length)
            {
                for (int p = i; p < a.returnStates.Length; p++)
                {
                    mergedParents[k]      = a.parents[p];
                    mergedReturnStates[k] = a.returnStates[p];
                    k++;
                }
            }
            else
            {
                for (int p = j; p < b.returnStates.Length; p++)
                {
                    mergedParents[k]      = b.parents[p];
                    mergedReturnStates[k] = b.returnStates[p];
                    k++;
                }
            }

            // trim merged if we combined a few that had same stack tops
            if (k < mergedParents.Length)
            {             // write index < last position; trim
                if (k == 1)
                {         // for just one merged element, return singleton top
                    PredictionContext a_ = SingletonPredictionContext.Create(mergedParents[0], mergedReturnStates[0]);
                    if (mergeCache != null)
                    {
                        mergeCache.Put(a, b, a_);
                    }
                    return(a_);
                }
                mergedParents      = Arrays.CopyOf(mergedParents, k);
                mergedReturnStates = Arrays.CopyOf(mergedReturnStates, k);
            }

            PredictionContext M = new ArrayPredictionContext(mergedParents, mergedReturnStates);

            // if we created same array as a or b, return that instead
            // TODO: track whether this is possible above during merge sort for speed
            if (M.Equals(a))
            {
                if (mergeCache != null)
                {
                    mergeCache.Put(a, b, a);
                }
                return(a);
            }
            if (M.Equals(b))
            {
                if (mergeCache != null)
                {
                    mergeCache.Put(a, b, b);
                }
                return(b);
            }

            CombineCommonParents(mergedParents);

            if (mergeCache != null)
            {
                mergeCache.Put(a, b, M);
            }
            return(M);
        }