Function encode_sparse_response 

pub fn encode_sparse_response(
    resp: &SparseResponse,
) -> Result<Vec<u8>, SparseWireError>

Encode a SparseResponse to the canonical wire bytes.

Layout:

offset  size  field
0       4     magic        = SPARSE_WIRE_MAGIC ("MSP1")
4       1     version      = SPARSE_WIRE_VERSION
5       32    tree_hash
37      32    bitmap_root
69      32    filter_hash
101     8     leaf_count   (u64 LE)
109     4     entries_len  (u32 LE) — count of TreeEntry items
113     ...   TreeEntry stream, each entry:
                u16 LE name_len   (1..=255)
                name_len bytes    (name; arbitrary bytes)
                u8          mode  (EntryMode)
                [u8; 32]    object_hash
...     4     bitmap_len   (u32 LE)
...     N     bitmap_bytes

Names are u16-LE length-prefixed rather than the u32 used by SPEC-OBJECTS — names are bounded at 255 bytes, so a u16 prefix is already overkill, and the four-byte saving per entry adds up over a large tree. The decoder rejects name_len == 0 and name_len > 255 to keep the bound enforced.

Errors

• SparseWireError::TooManyLeaves — manifest.leaf_count > MAX_LEAVES.
• SparseWireError::InvalidEntryName — an entry name is empty or

  255 bytes. Defensive: callers should reject before encoding.

• SparseWireError::TooLarge — the encoded buffer would exceed SPARSE_WIRE_MAX_BYTES.