Struct bonsaidb_core::key::VarInt

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pub struct VarInt<T>(pub T)
where
    T: VariableInteger;
Expand description

A wrapper type for Rust’s built-in integer types that encodes with variable length and implements the Key trait.

This type supports all of Rust’s built-in integer types:

  • u8
  • u16
  • u32
  • u64
  • u128
  • usize
  • i8
  • i16
  • i32
  • i64
  • i128
  • isize
use bonsaidb_core::key::{Key, KeyEncoding, VarInt};

#[derive(Key, Default, Clone)]
struct UserId(u64);

// `UserId` type will always encode to 8 bytes, since u64 will encode
// using `u64::to_be_bytes`.
let default_key_len = UserId::default().as_ord_bytes().unwrap().len();
assert_eq!(default_key_len, 8);
let another_key_len = UserId(u64::MAX).as_ord_bytes().unwrap().len();
assert_eq!(another_key_len, 8);

#[derive(Key, Default, Clone)]
struct UserIdVariable(VarInt<u64>);

// However, `UserIdVariable` will be able to encode in as little as 1 byte,
// but can take up to 9 bytes if the entire u64 range is utilized.
let default_key_len = UserIdVariable::default().as_ord_bytes().unwrap().len();
assert_eq!(default_key_len, 1);
let another_key_len = UserIdVariable(VarInt(u64::MAX))
    .as_ord_bytes()
    .unwrap()
    .len();
assert_eq!(another_key_len, 9);

Why does this type exist?

The Key trait is implemented for all of Rust’s native integer types by using to_be_bytes()/from_be_bytes(). This provides some benefits: very fast encoding and decoding, and known-width encoding is faster to decode.

This type uses [ordered_varint] to encode the types using a variable length encoding that is still compatible with the Key trait. This allows a value of 0 to encode as a single byte while still preserving the correct sort order required by Key.

Additionally, this encoding format allows for upgrading the in-memory size transparently if the value range needs increases over time. This only works between types that are signed the same.

Behavior with Serde

This type implements serde::Serialize and serde::Deserialize transparently, as many serialization formats implement native variable integer encoding, and do not benefit from an ordered implementation.

Tuple Fields§

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Trait Implementations§

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impl<T> Add<T> for VarInt<T>where T: Add<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the + operator.
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fn add(self, rhs: T) -> Self::Output

Performs the + operation. Read more
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impl<T> BitAnd<T> for VarInt<T>where T: BitAnd<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the & operator.
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fn bitand(self, rhs: T) -> Self::Output

Performs the & operation. Read more
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impl<T> BitOr<T> for VarInt<T>where T: BitOr<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the | operator.
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fn bitor(self, rhs: T) -> Self::Output

Performs the | operation. Read more
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impl<T> BitXor<T> for VarInt<T>where T: BitXor<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the ^ operator.
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fn bitxor(self, rhs: T) -> Self::Output

Performs the ^ operation. Read more
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impl<T> Clone for VarInt<T>where T: VariableInteger + Clone,

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fn clone(&self) -> VarInt<T>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<T> Debug for VarInt<T>where T: VariableInteger + Debug,

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

Formats the value using the given formatter. Read more
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impl<T> Default for VarInt<T>where T: VariableInteger + Default,

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fn default() -> VarInt<T>

Returns the “default value” for a type. Read more
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impl<T> Deref for VarInt<T>where T: VariableInteger,

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type Target = T

The resulting type after dereferencing.
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fn deref(&self) -> &Self::Target

Dereferences the value.
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impl<T> DerefMut for VarInt<T>where T: VariableInteger,

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fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.
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impl<'de, T> Deserialize<'de> for VarInt<T>where T: Deserialize<'de> + VariableInteger,

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fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more
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impl<T> Display for VarInt<T>where T: Display + VariableInteger,

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

Formats the value using the given formatter. Read more
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impl<T> Div<T> for VarInt<T>where T: Div<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the / operator.
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fn div(self, rhs: T) -> Self::Output

Performs the / operation. Read more
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impl<T> From<T> for VarInt<T>where T: VariableInteger,

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fn from(value: T) -> Self

Converts to this type from the input type.
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impl From<VarInt<i128>> for i128

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fn from(value: VarInt<i128>) -> Self

Converts to this type from the input type.
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impl From<VarInt<i16>> for i16

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fn from(value: VarInt<i16>) -> Self

Converts to this type from the input type.
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impl From<VarInt<i32>> for i32

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fn from(value: VarInt<i32>) -> Self

Converts to this type from the input type.
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impl From<VarInt<i64>> for i64

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fn from(value: VarInt<i64>) -> Self

Converts to this type from the input type.
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impl From<VarInt<i8>> for i8

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fn from(value: VarInt<i8>) -> Self

Converts to this type from the input type.
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impl From<VarInt<isize>> for isize

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fn from(value: VarInt<isize>) -> Self

Converts to this type from the input type.
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impl From<VarInt<u128>> for u128

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fn from(value: VarInt<u128>) -> Self

Converts to this type from the input type.
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impl From<VarInt<u16>> for u16

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fn from(value: VarInt<u16>) -> Self

Converts to this type from the input type.
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impl From<VarInt<u32>> for u32

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fn from(value: VarInt<u32>) -> Self

Converts to this type from the input type.
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impl From<VarInt<u64>> for u64

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fn from(value: VarInt<u64>) -> Self

Converts to this type from the input type.
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impl From<VarInt<u8>> for u8

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fn from(value: VarInt<u8>) -> Self

Converts to this type from the input type.
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impl From<VarInt<usize>> for usize

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fn from(value: VarInt<usize>) -> Self

Converts to this type from the input type.
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impl<T> Hash for VarInt<T>where T: VariableInteger + Hash,

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

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl<'k, T> Key<'k> for VarInt<T>where T: VariableInteger,

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const CAN_OWN_BYTES: bool = false

If true, this type can benefit from an owned Vec<u8>. This flag is used as a hint of whether to attempt to do memcpy operations in some decoding operations to avoid extra allocations.
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fn from_ord_bytes<'e>(bytes: ByteSource<'k, 'e>) -> Result<Self, Self::Error>

Deserialize a sequence of bytes previously encoded with KeyEncoding::as_ord_bytes.
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fn first_value() -> Result<Self, NextValueError>

Return the first value in sequence for this type. Not all types implement this.
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fn next_value(&self) -> Result<Self, NextValueError>

Return the next value in sequence for this type. Not all types implement this. Instead of wrapping/overflowing, None should be returned.
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impl<T> KeyEncoding for VarInt<T>where T: VariableInteger,

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type Error = Error

The error type that can be produced by either serialization or deserialization.
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const LENGTH: Option<usize> = None

The size of the key, if constant. If this type doesn’t produce the same number of bytes for each value, this should be None.
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fn describe<Visitor>(visitor: &mut Visitor)where Visitor: KeyVisitor,

Describes this type by invoking functions on visitor describing the key being encoded. Read more
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fn as_ord_bytes(&self) -> Result<Cow<'_, [u8]>, Self::Error>

Convert self into a Cow<'_, [u8]> containing bytes that are able to be compared via memcmp in a way that is comptaible with its own Ord implementation.
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impl<T> Mul<T> for VarInt<T>where T: Mul<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the * operator.
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fn mul(self, rhs: T) -> Self::Output

Performs the * operation. Read more
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impl<T> Not for VarInt<T>where T: Not<Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the ! operator.
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fn not(self) -> Self::Output

Performs the unary ! operation. Read more
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impl<T> Ord for VarInt<T>where T: VariableInteger + Ord,

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fn cmp(&self, other: &VarInt<T>) -> Ordering

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl<T> PartialEq for VarInt<T>where T: VariableInteger + PartialEq,

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fn eq(&self, other: &VarInt<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<T> PartialOrd for VarInt<T>where T: VariableInteger + PartialOrd,

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

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl<T> Rem<T> for VarInt<T>where T: Rem<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the % operator.
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fn rem(self, rhs: T) -> Self::Output

Performs the % operation. Read more
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impl<T> Serialize for VarInt<T>where T: Serialize + VariableInteger,

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fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>where S: Serializer,

Serialize this value into the given Serde serializer. Read more
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impl<T> Shl<T> for VarInt<T>where T: Shl<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the << operator.
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fn shl(self, rhs: T) -> Self::Output

Performs the << operation. Read more
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impl<T> Shr<T> for VarInt<T>where T: Shr<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the >> operator.
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fn shr(self, rhs: T) -> Self::Output

Performs the >> operation. Read more
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impl<T> Sub<T> for VarInt<T>where T: Sub<T, Output = T> + VariableInteger,

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type Output = VarInt<T>

The resulting type after applying the - operator.
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fn sub(self, rhs: T) -> Self::Output

Performs the - operation. Read more
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impl<T> Copy for VarInt<T>where T: VariableInteger + Copy,

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impl<T> Eq for VarInt<T>where T: VariableInteger + Eq,

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impl<T> StructuralEq for VarInt<T>where T: VariableInteger,

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impl<T> StructuralPartialEq for VarInt<T>where T: VariableInteger,

Auto Trait Implementations§

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impl<T> RefUnwindSafe for VarInt<T>where T: RefUnwindSafe,

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impl<T> Send for VarInt<T>

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impl<T> Sync for VarInt<T>

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impl<T> Unpin for VarInt<T>where T: Unpin,

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impl<T> UnwindSafe for VarInt<T>where T: UnwindSafe,

Blanket Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<!> for T

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fn from(t: !) -> T

Converts to this type from the input type.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided [Span], returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T> ToString for Twhere T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for Twhere V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a [WithDispatch] wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a [WithDispatch] wrapper. Read more
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impl<T> ApiError for Twhere T: Display + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync + Debug,

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impl<T> DeserializeOwned for Twhere T: for<'de> Deserialize<'de>,

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impl<T, Rhs, Output> NumOps<Rhs, Output> for Twhere T: Sub<Rhs, Output = Output> + Mul<Rhs, Output = Output> + Div<Rhs, Output = Output> + Add<Rhs, Output = Output> + Rem<Rhs, Output = Output>,