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cfg_if! {
if #[cfg(feature = "zstd_support")]
{
use zstd::bulk::Decompressor;
use super::compression_config::CompressionMode;
#[derive(Clone)]
pub struct Decoder {
result: Vec<u8>,
decoder: Option<Decompressor<'static>>,
}
impl Decoder {
pub fn new(compression_mode: CompressionMode) -> Self {
let decoder = match compression_mode {
CompressionMode::Training(_) => None,
CompressionMode::Default(_) => {
Some(Decompressor::new().expect("error creating Decompressor"))
}
CompressionMode::Dictionary(_, dictionary) => Some(
Decompressor::with_dictionary(&dictionary).expect("error creating Decompressor"),
),
};
Self {
decoder,
result: Vec::new(),
}
}
pub fn decode(&mut self, payload: &[u8]) -> &[u8] {
// First byte is the is_compressed flag (written by encoder)
let (is_compressed, data) = match payload.split_first() {
Some((&flag, rest)) => (flag != 0, rest),
None => {
self.result = Vec::new();
return &self.result;
}
};
if is_compressed {
if let Some(decoder) = &mut self.decoder {
self.result = decoder
.decompress(
data,
Decompressor::<'static>::upper_bound(data)
.expect("upper bound decode error"),
)
.expect("decode error");
return &self.result;
}
}
// Not compressed (or no decoder configured): return raw data
self.result = data.to_vec();
&self.result
}
}
}
else
{
use super::compression_config::CompressionMode;
/// Packet decoder (no-op variant: passes payload through unchanged).
#[derive(Clone)]
pub struct Decoder {
result: Vec<u8>,
}
impl Decoder {
/// Creates a no-op decoder (compression mode is ignored in this build variant).
pub fn new(_: CompressionMode) -> Self {
Self {
result: Vec::new(),
}
}
/// Returns the payload unchanged (no-op decompression).
pub fn decode(&mut self, payload: &[u8]) -> &[u8] {
self.result = payload.to_vec();
&self.result
}
}
}
}