value

Documentation

Overview

Package value contains methods for assisting with transformation of values in storage.

Index

• type Context
• type DefaultContext
  • func (c DefaultContext) AuthenticatedData() []byte
• type MutableTransformer
  • func NewMutableTransformer(transformer Transformer) *MutableTransformer
  • func (t *MutableTransformer) Set(transformer Transformer)
  • func (t *MutableTransformer) TransformFromStorage(data []byte, context Context) (out []byte, stale bool, err error)
  • func (t *MutableTransformer) TransformToStorage(data []byte, context Context) (out []byte, err error)
• type PrefixTransformer
• type Transformer
  • func NewPrefixTransformers(err error, transformers ...PrefixTransformer) Transformer

Types

type Context

type Context interface {
	// AuthenticatedData should return an array of bytes that describes the current value. If the value changes,
	// the transformer may report the value as unreadable or tampered. This may be nil if no such description exists
	// or is needed. For additional verification, set this to data that strongly identifies the value, such as
	// the key and creation version of the stored data.
	AuthenticatedData() []byte
}

Context is additional information that a storage transformation may need to verify the data at rest.

type DefaultContext

type DefaultContext []byte

DefaultContext is a simple implementation of Context for a slice of bytes.

func (DefaultContext) AuthenticatedData

func (c DefaultContext) AuthenticatedData() []byte

AuthenticatedData returns itself.

type MutableTransformer

type MutableTransformer struct {
	// contains filtered or unexported fields
}

MutableTransformer allows a transformer to be changed safely at runtime.

func NewMutableTransformer

func NewMutableTransformer(transformer Transformer) *MutableTransformer

NewMutableTransformer creates a transformer that can be updated at any time by calling Set()

func (*MutableTransformer) Set

func (t *MutableTransformer) Set(transformer Transformer)

Set updates the nested transformer.

func (*MutableTransformer) TransformFromStorage

func (t *MutableTransformer) TransformFromStorage(data []byte, context Context) (out []byte, stale bool, err error)

func (*MutableTransformer) TransformToStorage

func (t *MutableTransformer) TransformToStorage(data []byte, context Context) (out []byte, err error)

type PrefixTransformer

type PrefixTransformer struct {
	Prefix      []byte
	Transformer Transformer
}

PrefixTransformer holds a transformer interface and the prefix that the transformation is located under.

type Transformer

type Transformer interface {
	// TransformFromStorage may transform the provided data from its underlying storage representation or return an error.
	// Stale is true if the object on disk is stale and a write to etcd should be issued, even if the contents of the object
	// have not changed.
	TransformFromStorage(data []byte, context Context) (out []byte, stale bool, err error)
	// TransformToStorage may transform the provided data into the appropriate form in storage or return an error.
	TransformToStorage(data []byte, context Context) (out []byte, err error)
}

Transformer allows a value to be transformed before being read from or written to the underlying store. The methods must be able to undo the transformation caused by the other.

var IdentityTransformer Transformer = identityTransformer{}

IdentityTransformer performs no transformation of the provided data.

func NewPrefixTransformers

func NewPrefixTransformers(err error, transformers ...PrefixTransformer) Transformer

NewPrefixTransformers supports the Transformer interface by checking the incoming data against the provided prefixes in order. The first matching prefix will be used to transform the value (the prefix is stripped before the Transformer interface is invoked). The first provided transformer will be used when writing to the store.