Struct sequoia_openpgp::serialize::stream::padding::Padder

pub struct Padder<'a, P: Fn(u64) -> u64 + 'a> { /* fields omitted */ }

Pads a packet stream.

Writes a compressed data packet containing all packets written to this writer, and pads it according to the given policy.

The policy is a Fn(u64) -> u64, that given the number of bytes written to this writer N, computes the size the compression container should be padded up to. It is an error to return a number that is smaller than N.

Compatibility

This implementation uses the DEFLATE compression format. The packet structure contains a flag signaling the end of the stream (see Section 3.2.3 of RFC 1951), and any data appended after that is not part of the stream.

Section 9.3 of RFC 4880 recommends that this algorithm should be implemented, therefore support across various implementations should be good.

Examples

This example illustrates the use of Padder with the Padmé policy. Note that for brevity, the encryption and signature filters are omitted.

use std::io::Write;
use sequoia_openpgp as openpgp;
use openpgp::serialize::stream::{Message, LiteralWriter};
use openpgp::serialize::stream::padding::{Padder, padme};
use openpgp::types::CompressionAlgorithm;

let mut unpadded = vec![];
{
    let message = Message::new(&mut unpadded);
    // XXX: Insert Encryptor here.
    // XXX: Insert Signer here.
    let mut message = LiteralWriter::new(message).build()?;
    message.write_all(b"Hello world.")?;
    message.finalize()?;
}

let mut padded = vec![];
{
    let message = Message::new(&mut padded);
    // XXX: Insert Encryptor here.
    let message = Padder::new(message, padme)?;
    // XXX: Insert Signer here.
    let mut message = LiteralWriter::new(message).build()?;
    message.write_all(b"Hello world.")?;
    message.finalize()?;
}
assert!(unpadded.len() < padded.len());

Implementations

impl<'a, P: Fn(u64) -> u64 + 'a> Padder<'a, P>

pub fn new(inner: Message<'a>, p: P) -> Result<Message<'a>>

Creates a new padder with the given policy.

Examples

This example illustrates the use of Padder with the Padmé policy.

The most useful filter to push to the writer stack next is the Signer or the LiteralWriter. Finally, literal data must be wrapped using the LiteralWriter.

use sequoia_openpgp as openpgp;
use openpgp::serialize::stream::padding::{Padder, padme};

let message = Padder::new(message, padme)?;
// Optionally add a `Signer` here.
// Add a `LiteralWriter` here.

Trait Implementations

impl<'a, P: Fn(u64) -> u64 + 'a> Debug for Padder<'a, P>

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

Formats the value using the given formatter.

impl<'a, P: Fn(u64) -> u64 + 'a> Write for Padder<'a, P>

fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬 This is a nightly-only experimental API. (can_vector)

Determines if this Writeer has an efficient write_vectored implementation.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice]) -> Result<(), Error>

🔬 This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

Creates a "by reference" adaptor for this instance of Write.