ZSTD_sf_explicitBlockDelimiters
zret = zstd_cctx_set_param(ctx, ZSTD_c_blockDelimiters, ZSTD_sf_explicitBlockDelimiters);
bounds.upperBound = (int)ZSTD_sf_explicitBlockDelimiters;
if (mode == ZSTD_sf_explicitBlockDelimiters) {
assert(mode == ZSTD_sf_explicitBlockDelimiters);