Enum Compression 

#[non_exhaustive]
pub enum Compression {
    Raw,
    Zstd,
    Auto,
}

Compression negotiation vocabulary.

Drives the X-QWP-Accept-Encoding header the client sends on the WebSocket upgrade (Self::header_token returns the wire token). The server picks one codec from the advertised set and echoes its choice back in X-QWP-Content-Encoding; subsequent RESULT_BATCH frames are tagged with FLAG_ZSTD (or not) accordingly.

All three variants are usable end-to-end when the client is built with the sync-reader-zstd feature (which almost-all-features turns on by default). Without that feature, Zstd / Auto still compile but the decoder rejects any FLAG_ZSTD batch the server sends back with ErrorCode::UnsupportedServer — surface the error to the operator rather than silently mis-decoding a compressed payload as raw wire bytes.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Raw

Advertise raw only — every RESULT_BATCH body is uncompressed wire bytes. Works on every client build (no sync-reader-zstd dependency).

Zstd

Advertise zstd only — the server must send compressed batches and the client must be built with the sync-reader-zstd feature to decode them.

Auto

Advertise both zstd,raw — the server picks. The decoder handles either path. If the client was built without the sync-reader-zstd feature and the server still selects zstd, the decoder rejects the first FLAG_ZSTD batch with UnsupportedServer; the operator’s recovery is to enable the feature or pin Compression::Raw.

Implementations

impl Compression

pub fn accept_encoding(self, level: u8) -> String

Wire value for the X-QWP-Accept-Encoding header. Wire-egress.md §3: zstd carries an optional level=N hint that the server clamps to [1, 9]; raw has no parameters. Auto advertises zstd;level=N,raw (first match wins, per spec). level is ignored for Raw.

pub fn header_token(self) -> &'static str

Bare codec token without the level= parameter — useful for diagnostics and the (now-rare) callers that want to log just “raw” / “zstd” / “zstd,raw”. The on-wire value the client actually advertises is built by Self::accept_encoding.

Trait Implementations

impl Clone for Compression

fn clone(&self) -> Compression

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Compression

impl Debug for Compression

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Compression

impl PartialEq for Compression

fn eq(&self, other: &Compression) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Compression