## Quantity

# Struct Quantity

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    pub struct Quantity(pub String);

Expand description

Quantity is a fixed-point representation of a number. It provides convenient marshaling/unmarshaling in JSON and YAML, in addition to String() and AsInt64() accessors.

The serialization format is:

<quantity> ::= <signedNumber><suffix>

(Note that <suffix> may be empty, from the “” case in <decimalSI>.)

<digit> ::= 0 | 1 | … | 9 <digits> ::= <digit> | <digit><digits> <number> ::= <digits> | <digits>.<digits> | <digits>. | .<digits> <sign> ::= “+” | “-” <signedNumber> ::= <number> | <sign><number> <suffix> ::= <binarySI> | <decimalExponent> | <decimalSI> <binarySI> ::= Ki | Mi | Gi | Ti | Pi | Ei

(International System of units; See: http://physics.nist.gov/cuu/Units/binary.html)

<decimalSI> ::= m | “” | k | M | G | T | P | E

(Note that 1024 = 1Ki but 1000 = 1k; I didn’t choose the capitalization.)

<decimalExponent> ::= “e” <signedNumber> | “E” <signedNumber>

No matter which of the three exponent forms is used, no quantity may represent a number greater than 2^63-1 in magnitude, nor may it have more than 3 decimal places. Numbers larger or more precise will be capped or rounded up. (E.g.: 0.1m will rounded up to 1m.) This may be extended in the future if we require larger or smaller quantities.

When a Quantity is parsed from a string, it will remember the type of suffix it had, and will use the same type again when it is serialized.

Before serializing, Quantity will be put in “canonical form”. This means that Exponent/suffix will be adjusted up or down (with a corresponding increase or decrease in Mantissa) such that:

- No precision is lost - No fractional digits will be emitted - The exponent (or suffix) is as large as possible.

The sign will be omitted unless the number is negative.

Examples:

- 1.5 will be serialized as “1500m” - 1.5Gi will be serialized as “1536Mi”

Note that the quantity will NEVER be internally represented by a floating point number. That is the whole point of this exercise.

Non-canonical values will still parse as long as they are well formed, but will be re-emitted in their canonical form. (So always use canonical form, or don’t diff.)

This format is intended to make it difficult to use these numbers without writing some sort of special handling code in the hopes that that will cause implementors to also use a fixed point implementation.

## Tuple Fields§

§`0: String`

## Trait Implementations§

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### impl Clone for Quantity

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#### fn clone(&self) -> Quantity

Returns a duplicate 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 Debug for Quantity

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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 DeepMerge for Quantity

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#### fn merge_from(&mut self, other: Self)

Merge `other` into `self`.
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### impl Default for Quantity

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#### fn default() -> Quantity

Returns the “default value” for a type. Read more
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### impl<'de> Deserialize<'de> for Quantity

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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 PartialEq for Quantity

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

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

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

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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 StructuralPartialEq for Quantity

## Auto Trait Implementations§

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### impl Freeze for Quantity

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### impl RefUnwindSafe for Quantity

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### impl Send for Quantity

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### impl Sync for Quantity

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### impl Unpin for Quantity

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### impl UnwindSafe for Quantity

## Blanket Implementations§

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### impl<T> Any for T
where 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 T
where 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 T
where 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> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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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, U> Into<U> for T
where 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> ToOwned for T
where 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, U> TryFrom<U> for T
where 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 T
where 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<T> DeserializeOwned for T
where T: for<'de> Deserialize<'de>,