Constant MIN_TARGET_BLOCK_SIZE 

pub const MIN_TARGET_BLOCK_SIZE: u32 = 1340;

Smallest accepted block-size target (the ZSTD_TARGETCBLOCKSIZE_MIN bound): the single source of truth shared by the Rust setters (set_target_block_size) and the C ABI parameter surface. Smallest accepted block-size target (upstream ZSTD_TARGETCBLOCKSIZE_MIN): below this the per-block header overhead dominates any latency benefit. Re-exported at the crate root as the single source of truth; the C ABI parameter bounds import it from there.