keytransform

Documentation

Overview

Package keytransform introduces a Datastore Shim that transforms keys before passing them to its child. It can be used to manipulate what keys look like to the user, for example namespacing keys, reversing them, etc.

Use the Wrap function to wrap a datastore with any KeyTransform. A KeyTransform is simply an interface with two functions, a conversion and its inverse. For example:

import (
  ktds "github.com/jbenet/go-datastore/keytransform"
  ds "github.com/jbenet/go-datastore"
)

func reverseKey(k ds.Key) ds.Key {
  return k.Reverse()
}

func invertKeys(d ds.Datastore) {
  return ktds.Wrap(d, &ktds.Pair{
    Convert: reverseKey,
    Invert: reverseKey,  // reverse is its own inverse.
  })
}

Index

• type Datastore
  • func Wrap(child ds.Datastore, t KeyTransform) Datastore
• type KeyMapping
• type KeyTransform
• type Pair
  • func (t *Pair) ConvertKey(k ds.Key) ds.Key
  • func (t *Pair) InvertKey(k ds.Key) ds.Key

Types

type Datastore

type Datastore interface {
	ds.Shim
	KeyTransform

	Batch() (ds.Batch, error)
}

Datastore is a keytransform.Datastore

func Wrap

func Wrap(child ds.Datastore, t KeyTransform) Datastore

Wrap wraps a given datastore with a KeyTransform function. The resulting wrapped datastore will use the transform on all Datastore operations.

type KeyMapping

type KeyMapping func(ds.Key) ds.Key

KeyMapping is a function that maps one key to annother

type KeyTransform

type KeyTransform interface {
	ConvertKey(ds.Key) ds.Key
	InvertKey(ds.Key) ds.Key
}

KeyTransform is an object with a pair of functions for (invertibly) transforming keys

type Pair

type Pair struct {
	Convert KeyMapping
	Invert  KeyMapping
}

func (*Pair) ConvertKey

func (t *Pair) ConvertKey(k ds.Key) ds.Key

func (*Pair) InvertKey

func (t *Pair) InvertKey(k ds.Key) ds.Key