*
   * <p><b>Performance note:</b> The returned array has the same full memory footprint as this one
   * does (no actual copying is performed). To reduce memory usage, use {@code subArray(start,
   * end).trimmed()}.
   */
  public ImmutableDoubleArray subArray(int startIndex, int endIndex) {
    Preconditions.checkPositionIndexes(startIndex, endIndex, length());
    return startIndex == endIndex
        ? EMPTY

						const src = loadValue(sp + 32);
						if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
							this.mem.setUint8(sp + 48, 0);
							return;
						}
						const toCopy = src.subarray(0, dst.length);
						dst.set(toCopy);
						setInt64(sp + 40, toCopy.length);
						this.mem.setUint8(sp + 48, 1);
					},

					// func copyBytesToJS(dst ref, src []byte) (int, bool)