Struct DkimSigningStream 

pub struct DkimSigningStream<'a, T: SigningKey> { /* private fields */ }

A streaming DKIM signer that allows signing messages in chunks.

This is useful when you want to avoid loading the entire message into memory before signing. Headers are buffered internally until the header/body boundary is detected, then body content is streamed through the hasher.

Example

let signer = DkimSigner::from_key(key)
    .domain("example.com")
    .selector("default")
    .headers(["From", "To", "Subject"]);

let mut stream = signer.sign_streaming();
stream.write(b"From: sender@example.com\r\n");
stream.write(b"To: recipient@example.com\r\n");
stream.write(b"Subject: Test\r\n");
stream.write(b"\r\n");
stream.write(b"Body content here...");

let signature = stream.finish()?;

Implementations

impl<T: SigningKey> DkimSigningStream<'_, T>

pub fn write(&mut self, chunk: &[u8])

Feed a chunk of raw message data to the signer.

Data should be provided in order, starting with headers. The header/body boundary (\r\n\r\n) is automatically detected.

While reading headers, all data is buffered. Once the header/body boundary is detected, subsequent body data is streamed directly to the hasher.

pub fn finish(self) -> Result<Signature>

where <<T as SigningKey>::Hasher as HashImpl>::Context: HashContext,

Finalize the signature.

Consumes the stream and returns the DKIM signature. The current system time is used for the t= timestamp.

Errors

Returns an error if:

• No headers matching the signer’s header list were found
• The cryptographic signing operation fails
• finish() was already called