code: private int getBucketPlacementId(DocumentURI uri, int[][] buckets,
          int numBuckets, int numForests, int uForests) {
          String nk = LegacyAssignmentPolicy.normalize(uri.getUri());
          BigInteger uriKey=LegacyAssignmentPolicy.getUriKey(nk);
          long u = uriKey.longValue();
  
          for (int i = 14; i <= 56; i += 14) {
              u ^= uriKey.shiftRight(i).longValue();
          }
  
          int bucket = (int) (u&0x3fff);
          int fIdx = buckets[numForests - 1][bucket];
          boolean allUpdatble = numForests == uForests;
          if (!allUpdatble) {
              int[] partv = new int[uForests];
              int j = 0;
              for (int i = 0; i < numForests; i++) {
                  if (isUpdatable(i)) {
                      partv[j++] = i;
                  }
              }
              fIdx = partv[LegacyAssignmentPolicy.getPlacementId(uri, uForests)];
          }
          return fIdx;
      }
docs: return the index to the forest list (all forest - retired - RO/DO)