Struct VarZeroCow

pub struct VarZeroCow<'a, V: ?Sized> { /* private fields */ }

Copy-on-write type that efficiently represents VarULE types as their bitstream representation.

The primary use case for VarULE types is the ability to store complex variable-length datastructures inside variable-length collections like crate::VarZeroVec.

Underlying this ability is the fact that VarULE types can be efficiently represented as a flat bytestream.

In zero-copy cases, sometimes one wishes to unconditionally use this bytestream representation, for example to save stack size. A struct with five Cow<'a, str>s is not as stack-efficient as a single Cow containing the bytestream representation of, say, Tuple5VarULE<str, str, str, str, str>.

This type helps in this case: It is logically a Cow<'a, V>, with some optimizations, that is guaranteed to serialize as a byte stream in machine-readable scenarios.

During human-readable serialization, it will fall back to the serde impls on V, which ought to have a human-readable variant.

Implementations

impl<'a, V: VarULE + ?Sized> VarZeroCow<'a, V>

pub fn parse_bytes(bytes: &'a [u8]) -> Result<Self, UleError>

Construct from a slice. Errors if the slice doesn’t represent a valid V

pub fn parse_owned_bytes(bytes: Box<[u8]>) -> Result<Self, UleError>

Construct from an owned slice. Errors if the slice doesn’t represent a valid V

pub const unsafe fn from_bytes_unchecked(bytes: &'a [u8]) -> Self

Construct from a slice that is known to represent a valid V

Safety

bytes must be a valid V, i.e. it must successfully pass through V::parse_bytes() or V::validate_bytes().

pub fn from_encodeable<E: EncodeAsVarULE<V>>(encodeable: &E) -> Self

Construct this from an EncodeAsVarULE version of the contained type

Will always construct an owned version

pub fn new_borrowed(val: &'a V) -> Self

Construct a new borrowed version of this

pub fn new_owned(val: Box<V>) -> Self

Construct a new borrowed version of this

impl<'a, V: ?Sized> VarZeroCow<'a, V>

pub fn is_owned(&self) -> bool

Whether or not this is owned

pub fn as_bytes(&self) -> &[u8]

Get the byte representation of this type

Is also always a valid V and can be passed to V::from_bytes_unchecked()

Trait Implementations

impl<'a, V: ?Sized> Clone for VarZeroCow<'a, V>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'a, V: VarULE + ?Sized + Debug> Debug for VarZeroCow<'a, V>

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

Formats the value using the given formatter.

impl<'a, V: VarULE + ?Sized> Deref for VarZeroCow<'a, V>

type Target = V

The resulting type after dereferencing.

fn deref(&self) -> &V

Dereferences the value.

impl<'a, V: VarULE + ?Sized> EncodeAsVarULE<V> for VarZeroCow<'a, V>

fn encode_var_ule_as_slices<R>(&self, _: impl FnOnce(&[&[u8]]) -> R) -> R

Calls cb with a piecewise list of byte slices that when concatenated produce the memory pattern of the corresponding instance of T.

fn encode_var_ule_len(&self) -> usize

Return the length, in bytes, of the corresponding VarULE type

fn encode_var_ule_write(&self, dst: &mut [u8])

Write the corresponding VarULE type to the dst buffer. dst should be the size of Self::encode_var_ule_len()

impl<'a, V: VarULE + ?Sized> From<&'a V> for VarZeroCow<'a, V>

fn from(other: &'a V) -> Self

Converts to this type from the input type.

impl<'a, V: VarULE + ?Sized> From<Box<V>> for VarZeroCow<'a, V>

fn from(other: Box<V>) -> Self

Converts to this type from the input type.

impl<'a, V: VarULE + ?Sized + Ord> Ord for VarZeroCow<'a, V>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<'a, V: VarULE + ?Sized + PartialEq> PartialEq for VarZeroCow<'a, V>

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<'a, V: VarULE + ?Sized + PartialOrd> PartialOrd for VarZeroCow<'a, V>

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.

impl<'a, T: 'static + ?Sized> Yokeable<'a> for VarZeroCow<'static, T>

This impl requires enabling the optional yoke Cargo feature of the zerovec crate

type Output = VarZeroCow<'a, T>

This type MUST be Self with the 'static replaced with 'a, i.e. Self<'a>

fn transform(&'a self) -> &'a Self::Output

This method must cast self between &'a Self<'static> and &'a Self<'a>.

fn transform_owned(self) -> Self::Output

This method must cast self between Self<'static> and Self<'a>.

unsafe fn make(from: Self::Output) -> Self

This method can be used to cast away Self<'a>’s lifetime.

fn transform_mut<F>(&'a mut self, f: F)

where F: 'static + for<'b> FnOnce(&'b mut Self::Output),

This method must cast self between &'a mut Self<'static> and &'a mut Self<'a>, and pass it to f.

impl<'a, V: VarULE + ?Sized> ZeroFrom<'a, V> for VarZeroCow<'a, V>

fn zero_from(other: &'a V) -> Self

Clone the other C into a struct that may retain references into C.

impl<'a, 'b, V: VarULE + ?Sized> ZeroFrom<'a, VarZeroCow<'b, V>> for VarZeroCow<'a, V>

fn zero_from(other: &'a VarZeroCow<'b, V>) -> Self

Clone the other C into a struct that may retain references into C.

impl<'a, V: VarULE + ?Sized + Eq> Eq for VarZeroCow<'a, V>