ZSTD_sequenceBound
ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize);
size_t const maxNbExternalSeq = ZSTD_sequenceBound(blockSize);
size_t const maxNbExternalSeq = ZSTD_sequenceBound(blockSize);
zc->extSeqBufCapacity >= ZSTD_sequenceBound(srcSize)
assert(zc->seqCollector.seqIndex <= ZSTD_sequenceBound(srcSize));