Trait StreamObserver 

pub trait StreamObserver {
    // Provided methods
    fn begin(&mut self) { ... }
    fn before_read(&mut self) -> ObserverDecision { ... }
    fn before_write(&mut self, _: &[u8]) -> ObserverDecision { ... }
    fn after_write(&mut self, _: &[u8]) -> ObserverDecision { ... }
    fn end(&mut self, _: usize, _: Option<Box<&dyn Error>>) { ... }
}

Observe a stream’s operation when user code is not involved. For example: When you call EhRead.stream_to function, and you may want to calculate the checksum (SHA1, SHA256 or MD5 along the way, you can observe the stream copy using the observer)

Provided Methods

fn begin(&mut self)

Your observer’s begin will be called before stream copy If you plan to reuse the observer, you can reset it here

fn before_read(&mut self) -> ObserverDecision

Before the upstream is read. If you want to abort, abort it here by overriding the before_read()

fn before_write(&mut self, _: &[u8]) -> ObserverDecision

A chunk of data had been read from upstream, about to be written now You can intercept it by aborting it here

fn after_write(&mut self, _: &[u8]) -> ObserverDecision

A chunk of data had been written to down stream. You can intercept it by aborting it here

fn end(&mut self, _: usize, _: Option<Box<&dyn Error>>)

The copy ended and size bytes had been copied If there is error, err with be Some(cause) Note, different from Result<usize, Box>, the bytes copied is always given Even if it is zero

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors