Struct Tag

pub struct Tag(pub u64);

Facilitates caching of derived data.

Every time you look up a cert in the directory, the operation also returns a tag. This tag, which can be converted to a u64, is an opaque identifier that changes whenever the cert in the directory changes.

To use it, store the tag with your cached data, and every time you re-do the lookup, compare the returned tag with the stored tag to see if your cached data is still up-to-date.

Examples

This demonstrates how to use the tag to prevent useless recomputations.

let fp = "eb85bb5fa33a75e15e944e63f231550c4f47e38e";
let (tag, cert) = certd.get(fp)?.expect("cert to exist");
// ...
if let Some((new_cert, new_tag)) = certd.get_if_changed(tag, fp)? {
    // cert changed...
} else {
    // cert didn't change...
}

Tuple Fields

0: u64

Trait Implementations

impl Clone for Tag

fn clone(&self) -> Tag

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Tag

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

Formats the value using the given formatter.

impl From<Tag> for u64

fn from(t: Tag) -> Self

Converts to this type from the input type.

impl From<u64> for Tag

fn from(t: u64) -> Self

Converts to this type from the input type.

impl Hash for Tag

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Tag

fn eq(&self, other: &Tag) -> 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 TryFrom<&File> for Tag

fn try_from(fp: &File) -> Result<Self>

Compute a Tag from file metadata.

type Error = Error

The type returned in the event of a conversion error.

impl TryFrom<&Metadata> for Tag

fn try_from(m: &Metadata) -> Result<Self>

Compute a Tag from file metadata.

type Error = Error

The type returned in the event of a conversion error.

impl TryFrom<Metadata> for Tag

fn try_from(m: Metadata) -> Result<Self>

Compute a Tag from file metadata.

type Error = Error

The type returned in the event of a conversion error.

impl Copy for Tag

impl Eq for Tag

impl StructuralPartialEq for Tag