Struct milter::DataHandle

pub struct DataHandle<T> { /* fields omitted */ }

A handle on user data stored in the callback context.

DataHandle serves as an accessor to connection-local data that can be shared across callback functions within a connection.

Data life cycle

By design, data life cycle management is not automatic. It is the responsibility of a milter implementation to manage the data’s life cycle by reacquiring and disposing of context data (including associated resources such as file handles etc.) at an appropriate time in the callback flow.

As a rule of thumb, every path through the callback flow must have a final call to take.

Methods

impl<T> DataHandle<T>

pub fn replace(&self, data: T) -> Result<Option<T>>

Hands over data into the context, returning current context data if present.

Errors

An error variant is returned if the milter library encounters an error.

pub fn take(&self) -> Result<Option<T>>

Takes ownership of the current context data if present, and removes it from the context.

Errors

An error variant is returned if the milter library encounters an error.

pub fn borrow(&self) -> Result<Option<Ref<T>>>

Returns a reference to (borrows) the current context data if present.

It is the client’s responsibility to only call this when appropriate, that is, when the data is not already mutably borrowed.

Errors

An error variant is returned if the data is currently mutably borrowed.

Examples

if let Some(data) = context.data.borrow()? {
    println!("{}", data);
}

pub fn borrow_mut(&self) -> Result<Option<RefMut<T>>>

Returns a mutable reference to (mutably borrows) the current context data if present.

It is the client’s responsibility to only call this when appropriate, that is, when the data is not already borrowed.

Errors

An error variant is returned if the data is currently borrowed.

Examples

if let Some(mut msg_count) = context.data.borrow_mut()? {
    *msg_count += 1;
}

Trait Implementations

impl<T: Debug> Debug for DataHandle<T>

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

Formats the value using the given formatter.