ZSTD_limitCopy
size_t const loaded = ZSTD_limitCopy(
size_t const flushed = ZSTD_limitCopy(op, (size_t)(oend-op),
loadedSize = ZSTD_limitCopy(zds->inBuff + zds->inPos, toLoad, ip, (size_t)(iend-ip));
size_t const flushedSize = ZSTD_limitCopy(op, (size_t)(oend-op), zds->outBuff + zds->outStart, toFlushSize);