Crate version_track
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Version Track
This simple crate provides an easy way to track and compare changes to value that are too expensive to compare directly. This crate will track mutable changes to a value, and automatically increment a version number on every modification. Any comparison will then compare the internal version number, instead of having to do a full comparison on a complex data structure.
Tracking is performed by two values, the first is a V4 uuid::Uuid, and the second is a usize counter. The uuid::Uuid is generated once¹ per value being tracked, and then each subsequent mutable reference access increments the counter. This allows for tracking multiple distinct values independently, using the uuid::Uuid to track the different values across increments, and the counter to track direct changes to the value.
The crate provides two ways to track versions. The first way is using a pointer-like wrapper around another value. This is the easiest way to use this crate, but at times may result in extra unneeded version increments. To address this it is possible to create a version tracker manually to be added as a field on a struct or stored separately.
¹ The uuid::Uuid value may be regenerated is the usize counter wraps back to zero.
Basic Example
Any value can be wrapped with Versioned<T>, and because Versioned<T> implements std::ops::Deref,
std::ops::DerefMut, std::convert::AsRef and std::convert::AsMut, the wrapped value can be used in most places
that the wrapped value is used.
use version_track::Versioned;
let mut tracked_value = Versioned::new(String::from("foo"));
let current_version = tracked_value.version();
tracked_value.push_str("bar");
assert_ne!(current_version, tracked_value.version());
assert_eq!(*tracked_value, "foobar");Direct Use Example
Sometimes more control over the version is desired, or wrapping the value to be tracked is not possible. In those cases Version can be used directly. In this case, it is up to the developer to decide on when a change has occurred. This can be useful to only track some modifications to a value, or to only increment once when multiple mutable references are needed.
use version_track::Version;
let mut value = String::from("foo");
let mut version = Version::new();
let current_version = version;
value.push_str("bar");
version.increment();
assert_ne!(current_version, version);
assert_eq!(value, "foobar");