Function producer_parse_heap_bytes 

pub const fn producer_parse_heap_bytes(block_size: usize) -> usize

Heap bytes a compressor keeps for a SequenceProducer’s parse of blocks up to block_size bytes: room for sequence_bound sequences, as many as a parse it can use holds, kept from block to block (upstream reserves the same for its external sequences, zstd_compress.c:2236-2239).

use structured_zstd::encoding::sequences::{producer_parse_heap_bytes, sequence_bound};
assert_eq!(producer_parse_heap_bytes(131_072), sequence_bound(131_072) * 16);