Struct MigrationEdge 

pub struct MigrationEdge {
    pub from_epoch: u32,
    pub to_epoch: u32,
    pub migrator: fn(body: &mut [u8]) -> Result<(), ProgramError>,
}

One step in a layout’s migration chain.

An edge takes the raw account body (the bytes after the 16-byte Hopper header), mutates them in place to match the new epoch’s shape, and returns Ok(()) on success. The runtime then atomically bumps the header’s schema_epoch to to_epoch under the same mutable borrow.

Migration functions must not call CPIs (no CreateAccount, no Transfer) and must not resize the account (use realloc for that separately). They may read and write arbitrary bytes within the body, which is why the signature takes &mut [u8]. ZeroCopy safety has deliberately been stepped out of because the user is explicitly translating between two different byte layouts.

Fields

from_epoch: u32

Epoch the body is expected to be in before this edge runs.

to_epoch: u32

Epoch the body will be in after this edge runs successfully.

migrator: fn(body: &mut [u8]) -> Result<(), ProgramError>

In-place mutator. Called exactly once per upgrade sequence.

Implementations

impl MigrationEdge

pub const fn is_forward(&self) -> bool

Reject edges that would decrement or stay at the same epoch . migrations always move forward.

Trait Implementations

impl Clone for MigrationEdge

fn clone(&self) -> MigrationEdge

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for MigrationEdge