Struct Payload 

pub struct Payload<S, E>
where
    S: Stream<Item = Result<Bytes, E>> + Unpin,
    E: Into<Box<dyn StdErr + Send + Sync>>,
{
    pub expected_size: u64,
    pub stream: S,
}

A bundle that ties together a raw byte stream and its declared size.

This newtype exists to avoid “primitive obsession” — passing expected_size and stream as separate parameters to multiple layers of functions is error-prone. Bundling them enforces that the two always travel together.

The expected_size is used to pre-allocate disk space via fallocate before streaming begins, which improves performance on spinning drives and SD cards by preventing filesystem fragmentation.

Fields

expected_size: u64

The total number of bytes the client claims it will send. This is trusted for pre-allocation but validated at EOF.

stream: S

The raw async stream of byte chunks from the request body.

Implementations

impl<S, E> Payload<S, E>

where S: Stream<Item = Result<Bytes, E>> + Unpin, E: Into<Box<dyn StdErr + Send + Sync>>,

pub fn new<T>(expected_size: T, stream: S) -> Self

where T: Into<u64>,

Constructs a new Payload from an expected size and an async byte stream.

The expected_size accepts any type that can be converted to u64, so passing a u32 or usize directly is fine.