Enum Stored 

pub enum Stored<T> {
    Read(T),
    Unread {
        version: u32,
    },
}

A saved T, read whatever format version it was written in: see into_current.

Deserialising a T itself fails in the deserialiser on a value whose shape a later format changed, with an error that does not say why. A Stored<T> reads such a value as Unread, keeping only its top-level version field, so the version it was written in can still be reported.

Formats

Needs a self-describing format, such as JSON, because it tries T first and then the version field alone, which a format like bincode cannot. In such a format deserialise T itself: whatever restores it then checks FormatVersion::format_version.

It buffers the whole value while it reads it, so reading one takes about twice its memory.

Variants

Read(T)

The value read as a T.

Unread

A value that does not read as a T, written in format version version.

Fields

version: u32

The value’s top-level version field.

Implementations

impl<T: FormatVersion> Stored<T>

pub fn into_current(self) -> Result<T, StoredFormatError>

The value, if it was written in the format version this release reads.

Errors

• StoredFormatError::UnsupportedVersion if it was written in another version, whether or not its shape still reads as a T.
• StoredFormatError::Malformed if it claims this release’s version but does not read as a T, such as a value edited by hand. Deserialise a T itself to learn why.

Trait Implementations

impl<T: Clone> Clone for Stored<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for Stored<T>

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

Formats the value using the given formatter.

impl<'de, T> Deserialize<'de> for Stored<T>

where T: Deserialize<'de>,

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T: Eq> Eq for Stored<T>

impl<T: PartialEq> PartialEq for Stored<T>

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

Equality operator ==.

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

Inequality operator !=.

impl<T: PartialEq> StructuralPartialEq for Stored<T>