@VisibleForTesting long getNextGenerationStampV1() throws IOException { long genStampV1 = generationStampV1.nextValue(); if (genStampV1 >= generationStampV1Limit) { // We ran out of generation stamps for legacy blocks. In practice, it // is extremely unlikely as we reserved 1T v1 generation stamps. The // result is that we can no longer append to the legacy blocks that // were created before the upgrade to sequential block IDs. throw new OutOfV1GenerationStampsException(); } return genStampV1; }