Struct Ring

pub struct Ring<T> {
    pub mmap: RingMmap<T>,
    pub len: usize,
    pub mod_mask: u32,
}

A generic, safe wrapper for an AF_XDP ring buffer.

This struct provides safe methods to interact with a memory-mapped ring, handling atomic operations for producer/consumer indices and access to descriptors.

Fields

mmap: RingMmap<T>

The memory-mapped components of the ring.

len: usize

The number of descriptors the ring can hold.

mod_mask: u32

A mask used for wrapping around the ring (len - 1).

Implementations

impl<T> Ring<T>

where T: Copy,

pub fn frame_size(&self) -> u64

Returns the size of a single UMEM frame.

pub fn mmap( fd: i32, len: usize, ring_type: u64, offsets: &xdp_ring_offset, ) -> Result<Self, Error>

Memory-maps a ring from a file descriptor.

How it works

This function calls the lower-level mmap_ring function to perform the mmap syscall with the correct offsets for the given ring type. It then initializes a Ring struct to manage the mapped memory.

pub fn consumer(&self) -> u32

Atomically reads the consumer index of the ring.

pub fn producer(&self) -> u32

Atomically reads the producer index of the ring.

pub fn update_producer(&mut self, value: u32)

Atomically updates the producer index of the ring.

pub fn update_consumer(&mut self, value: u32)

Atomically updates the consumer index of the ring.

pub fn flags(&self) -> u32

Atomically reads the flags of the ring.

Flags can indicate states like XDP_RING_NEED_WAKEUP.

pub fn increment(&self, value: &mut u32) -> u32

Increments a value, wrapping it around the ring size.

pub fn mut_desc_at(&mut self, index: u32) -> &mut T

Returns a mutable reference to the descriptor at a given index.

Panics

This function will panic in debug builds if the index is out of bounds.

pub fn desc_at(&self, index: u32) -> T

Returns a copy of the descriptor at a given index.

Panics

This function will panic in debug builds if the index is out of bounds.

impl Ring<u64>

pub fn fill(&mut self, start_frame: u32)

Fills the ring (typically the Fill Ring) with UMEM frame addresses.

Arguments

• start_frame - The starting frame number to begin filling from.

impl Ring<XdpDesc>

pub fn fill(&mut self, start_frame: u32)

Fills the ring (typically the TX ring) with default XdpDesc values.

This pre-populates the ring with descriptors pointing to corresponding UMEM frames.

Arguments

• start_frame - The starting frame number to begin filling from.

pub fn set(&mut self, index: u32, len: u32)

Sets the descriptor at index to a specific length.

The address is calculated based on the index and frame size.

Trait Implementations

impl<T: Default> Default for Ring<T>

fn default() -> Ring<T>

Returns the “default value” for a type.