kvs

Documentation

Overview

Package kvs implements a write-once key-value store with different storage backends.

Index

• Variables
• func TransformByteIndex(in string) []string
• func TransformIdentity(in string) []string
• type Store
  • func NewTranscoder(store Store, tcoder Transcoder, fileExt string) Store
• type StoreReader
• type Transcoder
• type Writer

Variables

var (
	// ErrNotFound is returned if a key does not exist
	ErrNotFound = errors.New("key not found")

	// ErrExists is returned if a key already exists
	ErrExists = errors.New("key already exists")

	// ErrReadOnly is returned if a write operation is attempted on a read-only
	// interface. Read-only interfaces are implemented as kvs.Store internally
	// for compatibility with other layers but exposing a kvs.StoreReader is
	// best practice in that case.
	ErrReadOnly = errors.New("write attempted on read only data source")
)

Functions

func TransformByteIndex

func TransformByteIndex(in string) []string

TransformByteIndex splits the first hex byte off of a hash string and uses it as a directory name. Note that the filename inside this index directory has the first byte removed.

For example, the MD5 hash "4f41243847da693a4f356c0486114bc6" would be transformed to:

[]string{"4f", "41243847da693a4f356c0486114bc6"}

This transform is used if another function is not provided.

func TransformIdentity

func TransformIdentity(in string) []string

TransformIdentity is a transform function that returns the input key unchanged

Types

type Store

type Store interface {
	Exists(key string) (bool, error)
	Read(key string) ([]byte, error)
	ReadStream(key string) (io.ReadCloser, error)
	Write(key string, data []byte) error
	WriteStream(key string, reader io.Reader) error
	Remove(key string) error
}

Store represents the atomic writing functions for a write-once KVS repository

func NewTranscoder

func NewTranscoder(store Store, tcoder Transcoder, fileExt string) Store

NewTranscoder returns a TranscoderStore given a base Store, a Transcoder, and an optional file extension

type StoreReader

type StoreReader interface {
	Read(key string) ([]byte, error)
	ReadStream(key string) (io.ReadCloser, error)
	Exists(key string) (bool, error)
}

StoreReader represents the atomic reading functoins for a write-once KVS repository

type Transcoder

type Transcoder interface {
	NewWriter(io.Writer) (io.WriteCloser, error)
	NewReader(io.ReadCloser) (io.ReadCloser, error)
}

Transcoder represents an invertible pair of streaming encoder/decoder functions

type Writer

type Writer interface {
	io.WriteCloser
	Abort() error
}

Writer is a wrapper for a WriteCloser interface with an abort function