Struct DictionaryKeyEncoder 

pub struct DictionaryKeyEncoder { /* private fields */ }

Compact dictionary encoder that maps variable-length byte keys to u32 codes.

Pre-populate during query setup (Ring 2), then use the fast encode() path during event processing (Ring 0). The encoder is Send for transfer to reactor threads but not Sync — it’s designed for single-threaded access.

Implementations

impl DictionaryKeyEncoder

pub fn new() -> Self

Creates a new empty encoder.

pub fn with_capacity(capacity: usize) -> Self

Creates a new encoder with pre-allocated capacity.

Use this when the approximate number of distinct keys is known (e.g., number of ticker symbols, region names).

pub fn encode(&self, key: &[u8]) -> Option<u32>

Encodes a key to its compact u32 code (Ring 0 hot path).

Returns None if the key has not been inserted. This is a pure hash map lookup with no allocation.

pub fn encode_or_insert(&mut self, key: &[u8]) -> Option<u32>

Encodes a key, inserting it if not already present (Ring 2 setup).

Allocates on first insertion of a new key. Subsequent calls for the same key return the existing code without allocation.

Errors

Returns None if the dictionary already contains u32::MAX keys.

pub fn decode(&self, code: u32) -> Option<&[u8]>

Decodes a compact code back to the original key bytes.

Returns None if the code is out of range.

pub fn encode_to_bytes(&self, key: &[u8]) -> Option<[u8; 4]>

Returns the encoded key as a 4-byte little-endian slice.

Useful for passing encoded keys to state stores that expect &[u8].

pub fn len(&self) -> usize

Returns the number of distinct keys in the dictionary.

pub fn is_empty(&self) -> bool

Returns true if the dictionary is empty.

pub fn clear(&mut self)

Clears the dictionary, removing all mappings.

Trait Implementations

impl Default for DictionaryKeyEncoder

fn default() -> Self

Returns the “default value” for a type.