resource

Documentation

Index

• Constants
• Variables
• func NewQuantityFlagValue(q *Quantity) flag.Value
• type Format
• type Quantity
  • func MustParse(str string) Quantity
  • func NewMilliQuantity(value int64, format Format) *Quantity
  • func NewQuantity(value int64, format Format) *Quantity
  • func NewScaledQuantity(value int64, scale Scale) *Quantity
  • func ParseQuantity(str string) (*Quantity, error)
  • func QuantityFlag(flagName, defaultValue, description string) *Quantity
  • func (q *Quantity) Add(y Quantity) error
  • func (q *Quantity) Canonicalize() (string, suffix)
  • func (q *Quantity) Cmp(y Quantity) int
  • func (q *Quantity) Copy() *Quantity
  • func (q Quantity) MarshalJSON() ([]byte, error)
  • func (q *Quantity) MilliValue() int64
  • func (q *Quantity) Neg(y Quantity) error
  • func (q *Quantity) ScaledValue(scale Scale) int64
  • func (q *Quantity) Set(value int64)
  • func (q *Quantity) SetMilli(value int64)
  • func (q *Quantity) SetScaled(value int64, scale Scale)
  • func (q *Quantity) String() string
  • func (q *Quantity) Sub(y Quantity) error
  • func (q *Quantity) UnmarshalJSON(value []byte) error
  • func (q *Quantity) Value() int64
• type Scale

Constants

const (
	DecimalExponent = Format("DecimalExponent") // e.g., 12e6
	BinarySI        = Format("BinarySI")        // e.g., 12Mi (12 * 2^20)
	DecimalSI       = Format("DecimalSI")       // e.g., 12M  (12 * 10^6)
)

Variables

var (

	// Errors that could happen while parsing a string.
	ErrFormatWrong = errors.New("quantities must match the regular expression '" + splitREString + "'")
	ErrNumeric     = errors.New("unable to parse numeric part of quantity")
	ErrSuffix      = errors.New("unable to parse quantity's suffix")

	// The maximum value we can represent milli-units for.
	// Compare with the return value of Quantity.Value() to
	// see if it's safe to use Quantity.MilliValue().
	MaxMilliValue = int64(((1 << 63) - 1) / 1000)
)

Functions

func NewQuantityFlagValue

func NewQuantityFlagValue(q *Quantity) flag.Value

NewQuantityFlagValue returns an object that can be used to back a flag, pointing at the given Quantity variable.

Types

type Format

type Format string

Format lists the three possible formattings of a quantity.

type Quantity

type Quantity struct {
	// Amount is public, so you can manipulate it if the accessor
	// functions are not sufficient.
	Amount *inf.Dec

	// Change Format at will. See the comment for Canonicalize for
	// more details.
	Format
}

Quantity is a fixed-point representation of a number. It provides convenient marshaling/unmarshaling in JSON and YAML, in addition to String() and Int64() 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:

a. No precision is lost
b. No fractional digits will be emitted
c. 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: We reserve the right to amend this canonical format, perhaps to

allow 1.5 to be canonical.

TODO: Remove above disclaimer after all bikeshedding about format is over,

or after March 2015.

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.

+protobuf=true +protobuf.embed=QuantityProto +protobuf.options.marshal=false +protobuf.options.(gogoproto.goproto_stringer)=false

func MustParse

func MustParse(str string) Quantity

MustParse turns the given string into a quantity or panics; for tests or others cases where you know the string is valid.

func NewMilliQuantity

func NewMilliQuantity(value int64, format Format) *Quantity

NewMilliQuantity returns a new Quantity representing the given value * 1/1000 in the given format. Note that BinarySI formatting will round fractional values, and will be changed to DecimalSI for values x where (-1 < x < 1) && (x != 0).

func NewQuantity

func NewQuantity(value int64, format Format) *Quantity

NewQuantity returns a new Quantity representing the given value in the given format.

func NewScaledQuantity

func NewScaledQuantity(value int64, scale Scale) *Quantity

NewScaledQuantity returns a new Quantity representing the given value * 10^scale in DecimalSI format.

func ParseQuantity

func ParseQuantity(str string) (*Quantity, error)

ParseQuantity turns str into a Quantity, or returns an error.

func QuantityFlag

func QuantityFlag(flagName, defaultValue, description string) *Quantity

QuantityFlag is a helper that makes a quantity flag (using standard flag package). Will panic if defaultValue is not a valid quantity.

func (*Quantity) Add

func (q *Quantity) Add(y Quantity) error

func (*Quantity) Canonicalize

func (q *Quantity) Canonicalize() (string, suffix)

Canonicalize returns the canonical form of q and its suffix (see comment on Quantity).

Note about BinarySI:

• If q.Format is set to BinarySI and q.Amount represents a non-zero value between -1 and +1, it will be emitted as if q.Format were DecimalSI.
• Otherwise, if q.Format is set to BinarySI, frational parts of q.Amount will be rounded up. (1.1i becomes 2i.)

func (*Quantity) Cmp

func (q *Quantity) Cmp(y Quantity) int

Cmp compares q and y and returns:

-1 if q <  y
 0 if q == y
+1 if q >  y

func (*Quantity) Copy

func (q *Quantity) Copy() *Quantity

Copy is a convenience function that makes a deep copy for you. Non-deep copies of quantities share pointers and you will regret that.

func (Quantity) MarshalJSON

func (q Quantity) MarshalJSON() ([]byte, error)

MarshalJSON implements the json.Marshaller interface.

func (*Quantity) MilliValue

func (q *Quantity) MilliValue() int64

MilliValue returns the value of ceil(q * 1000); this could overflow an int64; if that's a concern, call Value() first to verify the number is small enough.

func (*Quantity) Neg

func (q *Quantity) Neg(y Quantity) error

Neg sets q to the negative value of y. It updates the format of q to match y.

func (*Quantity) ScaledValue

func (q *Quantity) ScaledValue(scale Scale) int64

ScaledValue returns the value of ceil(q * 10^scale); this could overflow an int64. To detect overflow, call Value() first and verify the expected magnitude.

func (*Quantity) Set

func (q *Quantity) Set(value int64)

Set sets q's value to be value.

func (*Quantity) SetMilli

func (q *Quantity) SetMilli(value int64)

SetMilli sets q's value to be value * 1/1000.

func (*Quantity) SetScaled

func (q *Quantity) SetScaled(value int64, scale Scale)

SetScaled sets q's value to be value * 10^scale

func (*Quantity) String

func (q *Quantity) String() string

String formats the Quantity as a string.

func (*Quantity) Sub

func (q *Quantity) Sub(y Quantity) error

func (*Quantity) UnmarshalJSON

func (q *Quantity) UnmarshalJSON(value []byte) error

UnmarshalJSON implements the json.Unmarshaller interface.

func (*Quantity) Value

func (q *Quantity) Value() int64

Value returns the value of q; any fractional part will be lost.

type Scale

type Scale int

Scale is used for getting and setting the base-10 scaled value. Base-2 scales are omitted for mathematical simplicity. See Quantity.ScaledValue for more details.

const (
	Nano  Scale = -9
	Micro Scale = -6
	Milli Scale = -3
	Kilo  Scale = 3
	Mega  Scale = 6
	Giga  Scale = 9
	Tera  Scale = 12
	Peta  Scale = 15
	Exa   Scale = 18
)