Pinning in Rust
The following diagram shows a slightly more complex self-referential struct so that we have something visual to help us understand:
Figure 9.3 – Moving a self-referential struct with three fields
At a very high level, pinning makes it possible to rely on data that has a stable memory address by disallowing any operation that might move it:
Figure 9.4 – Moving a pinned struct
The concept of pinning is pretty simple. The complex part is how it’s implemented in the language and how it’s used.
Pinning in theory
Pinning is a part of Rust’s standard library and consists of two parts: the type, Pin, and the marker-trait, Unpin. Pinning is only a language construct. There is no special kind of location or memory that you move values to so they get pinned. There is no syscall to ask the operating system to ensure a value stays the same place in memory. It’s only a part...
