Struct VerLink 

pub struct VerLink { /* private fields */ }

A linked list tracking a logic “version” with compatibility rules:

• Append-only changes bump the version, the new version is backwards compatible.
• Non-append-only changes create a new version that is incompatible with all other versions (in the current process).
• Clones (cheaply) preserve the version.

Supported operations:

• new() -> x: Create a new version that is not comparable (compatible) with other versions.
• clone(x) -> y: Clone x to y. x == y. x and y are compatible.
• bump(x) -> y: Bump x to y. y > x. y is backwards-compatible with x. Note: y is not comparable (compatible) with other bump(x).
• x > y: true if x is backwards compatible with y.

The linked list can be shared in other linked lists. So they form a tree effectively. Comparing to a DAG, there is no “merge” operation. Compatibility questions become reachability questions.

Implementations

impl VerLink

pub fn new() -> Self

Creates a new VerLink that is incompatible with all other VerLinks in the process.

pub fn bump(&mut self)

Bumps the VerLink for backward-compatible (ex. append-only) changes. Note the “append-only” means only adding commits without “stripping” or “rewriting” commits. It is different from the “append-only” concept from the storage layer, because the “stripping” or “rewriting” might be implemented as “appending” special data on the storage layer.

impl VerLink

pub fn clear_storage_version_cache()

Clear the cache that maps storage version to VerLink.

pub fn from_storage_version( str_id: &str, version: (u64, u64), ) -> Option<VerLink>

Lookup a VerLink from a given storage version.

pub fn associate_storage_version(&self, str_id: String, version: (u64, u64))

Associate the VerLink with a storage version.

pub fn from_storage_version_or_new(str_id: &str, version: (u64, u64)) -> VerLink

Lookup a VerLink from a given storage version, or create a new VerLink and remember it in cache.

Trait Implementations

impl Clone for VerLink

fn clone(&self) -> VerLink

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for VerLink

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

Formats the value using the given formatter.

impl<'a> From<&'a VerLink> for DagVersion<'a>

fn from(version: &'a VerLink) -> Self

Converts to this type from the input type.

impl<'a> From<&'a VerLink> for IdMapVersion<'a>

fn from(version: &'a VerLink) -> Self

Converts to this type from the input type.

impl PartialEq for VerLink

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for VerLink

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.