packr

README

Packr (v2)

Packr is a simple solution for bundling static assets inside of Go binaries. Most importantly it does it in a way that is friendly to developers while they are developing.

Intro Video

To get an idea of the what and why of Packr, please enjoy this short video: https://vimeo.com/219863271.

Library Installation

$ go get -u github.com/gobuffalo/packr/v2/...

Binary Installation

$ go get -u github.com/gobuffalo/packr/v2/packr2

New File Format FAQs

In version v2.0.0 the file format changed and is not backward compatible with the packr-v1.x library.

Can packr-v1.x read the new format?

No, it can not. Because of the way the new file format works porting it to packr-v1.x would be difficult. PR's are welcome though. :)

Can packr-v2.x read packr-v1.x files?

Yes it can, but that ability will eventually be phased out. Because of that we recommend moving to the new format.

Can packr-v2.x generate packr-v1.x files?

Yes it can, but that ability will eventually be phased out. Because of that we recommend moving to the new format.

The --legacy command is available on all commands that generate -packr.go files.

$ packr2 --legacy
$ packr2 install --legacy
$ packr2 build --legacy

Usage

In Code

The first step in using Packr is to create a new box. A box represents a folder on disk. Once you have a box you can get string or []byte representations of the file.

// set up a new box by giving it a name and an optional (relative) path to a folder on disk:
box := packr.New("My Box", "./templates")

// Get the string representation of a file, or an error if it doesn't exist:
html, err := box.FindString("index.html")

// Get the []byte representation of a file, or an error if it doesn't exist:
html, err := box.Find("index.html")

What is a Box?

A box represents a folder, and any sub-folders, on disk that you want to have access to in your binary. When compiling a binary using the packr2 CLI the contents of the folder will be converted into Go files that can be compiled inside of a "standard" go binary. Inside of the compiled binary the files will be read from memory. When working locally the files will be read directly off of disk. This is a seamless switch that doesn't require any special attention on your part.

Example

Assume the follow directory structure:

├── main.go
└── templates
    ├── admin
    │   └── index.html
    └── index.html

The following program will read the ./templates/admin/index.html file and print it out.

package main

import (
  "fmt"

  "github.com/gobuffalo/packr/v2"
)

func main() {
  box := packr.New("myBox", "./templates")

  s, err := box.FindString("admin/index.html")
  if err != nil {
    log.Fatal(err)
  }
  fmt.Println(s)
}

Development Made Easy

In order to get static files into a Go binary, those files must first be converted to Go code. To do that, Packr, ships with a few tools to help build binaries. See below.

During development, however, it is painful to have to keep running a tool to compile those files.

Packr uses the following resolution rules when looking for a file:

1. Look for the file in-memory (inside a Go binary)
2. Look for the file on disk (during development)

Because Packr knows how to fall through to the file system, developers don't need to worry about constantly compiling their static files into a binary. They can work unimpeded.

Packr takes file resolution a step further. When declaring a new box you use a relative path, ./templates. When Packr recieves this call it calculates out the absolute path to that directory. By doing this it means you can be guaranteed that Packr can find your files correctly, even if you're not running in the directory that the box was created in. This helps with the problem of testing, where Go changes the pwd for each package, making relative paths difficult to work with. This is not a problem when using Packr.

---

Usage with HTTP

A box implements the http.FileSystem interface, meaning it can be used to serve static files.

package main

import (
	"net/http"

	"github.com/gobuffalo/packr/v2"
)

func main() {
	box := packr.New("someBoxName", "./templates")

	http.Handle("/", http.FileServer(box))
	http.ListenAndServe(":3000", nil)
}

---

Building a Binary (the easy way)

When it comes time to build, or install, your Go binary, simply use packr2 build or packr2 install just as you would go build or go install. All flags for the go tool are supported and everything works the way you expect, the only difference is your static assets are now bundled in the generated binary. If you want more control over how this happens, looking at the following section on building binaries (the hard way).

Building a Binary (the hard way)

Before you build your Go binary, run the packr2 command first. It will look for all the boxes in your code and then generate .go files that pack the static files into bytes that can be bundled into the Go binary.

$ packr2

Then run your go build command like normal.

NOTE: It is not recommended to check-in these generated -packr.go files. They can be large, and can easily become out of date if not careful. It is recommended that you always run packr2 clean after running the packr2 tool.

Cleaning Up

When you're done it is recommended that you run the packr2 clean command. This will remove all of the generated files that Packr created for you.

$ packr2 clean

Why do you want to do this? Packr first looks to the information stored in these generated files, if the information isn't there it looks to disk. This makes it easy to work with in development.

---

Debugging

The packr2 command passes all arguments down to the underlying go command, this includes the -v flag to print out go build information. Packr looks for the -v flag, and will turn on its own verbose logging. This is very useful for trying to understand what the packr command is doing when it is run.

Documentation

Index

• Constants
• Variables
• func PackBytes(box string, name string, bb []byte)
• func PackBytesGzip(box string, name string, bb []byte) error
• func PackJSONBytes(box string, name string, jbb string) error
• type Box
  • func New(name string, path string) *Box
  • func NewBox(path string) *Box
  • func (b *Box) AddBytes(path string, t []byte) error
  • func (b *Box) AddString(path string, t string) error
  • func (b Box) Bytes(name string) []byte
  • func (b Box) Find(name string) ([]byte, error)
  • func (b Box) FindString(name string) (string, error)
  • func (b Box) Has(name string) bool
  • func (b Box) List() []string
  • func (b Box) MustBytes(name string) ([]byte, error)
  • func (b Box) MustString(name string) (string, error)
  • func (b Box) Open(name string) (http.File, error)
  • func (b *Box) Resolve(key string) (file.File, error)
  • func (b *Box) SetResolver(file string, res resolver.Resolver)
  • func (b Box) String(name string) string
  • func (b *Box) Walk(wf WalkFunc) error
  • func (b Box) WalkPrefix(prefix string, wf WalkFunc) error
• type File
• type Pointer
  • func (p Pointer) Resolve(box string, path string) (file.File, error)
• type WalkFunc

Constants

const Version = "v2.0.0-rc.15"

Variables

var (
	// ErrResOutsideBox gets returned in case of the requested resources being outside the box
	// Deprecated
	ErrResOutsideBox = errors.New("can't find a resource outside the box")
)

Functions

func PackBytes

func PackBytes(box string, name string, bb []byte)

PackBytes packs bytes for a file into a box. Deprecated

func PackBytesGzip

func PackBytesGzip(box string, name string, bb []byte) error

PackBytesGzip packets the gzipped compressed bytes into a box. Deprecated

func PackJSONBytes

func PackJSONBytes(box string, name string, jbb string) error

PackJSONBytes packs JSON encoded bytes for a file into a box. Deprecated

Types

type Box

type Box struct {
	Path            string            `json:"path"`
	Name            string            `json:"name"`
	ResolutionDir   string            `json:"resolution_dir"`
	DefaultResolver resolver.Resolver `json:"default_resolver"`
	// contains filtered or unexported fields
}

Box represent a folder on a disk you want to have access to in the built Go binary.

func New

func New(name string, path string) *Box

func NewBox

func NewBox(path string) *Box

NewBox returns a Box that can be used to retrieve files from either disk or the embedded binary.

func (*Box) AddBytes

func (b *Box) AddBytes(path string, t []byte) error

AddBytes sets t in b.data by the given path

func (*Box) AddString

func (b *Box) AddString(path string, t string) error

AddString converts t to a byteslice and delegates to AddBytes to add to b.data

func (Box) Bytes

func (b Box) Bytes(name string) []byte

Bytes is deprecated. Use Find instead

func (Box) Find

func (b Box) Find(name string) ([]byte, error)

Find returns either the byte slice of the requested file or an error if it can not be found.

func (Box) FindString

func (b Box) FindString(name string) (string, error)

FindString returns either the string of the requested file or an error if it can not be found.

func (Box) Has

func (b Box) Has(name string) bool

Has returns true if the resource exists in the box

func (Box) List

func (b Box) List() []string

List shows "What's in the box?"

func (Box) MustBytes

func (b Box) MustBytes(name string) ([]byte, error)

MustBytes is deprecated. Use Find instead.

func (Box) MustString

func (b Box) MustString(name string) (string, error)

MustString is deprecated. Use FindString instead

func (Box) Open

func (b Box) Open(name string) (http.File, error)

Open returns a File using the http.File interface

func (*Box) Resolve

func (b *Box) Resolve(key string) (file.File, error)

func (*Box) SetResolver

func (b *Box) SetResolver(file string, res resolver.Resolver)

func (Box) String

func (b Box) String(name string) string

String is deprecated. Use FindString instead

func (*Box) Walk

func (b *Box) Walk(wf WalkFunc) error

Walk will traverse the box and call the WalkFunc for each file in the box/folder.

func (Box) WalkPrefix

func (b Box) WalkPrefix(prefix string, wf WalkFunc) error

WalkPrefix will call box.Walk and call the WalkFunc when it finds paths that have a matching prefix

type File

type File = file.File

File has been deprecated and file.File should be used instead

type Pointer

type Pointer struct {
	ForwardBox  string
	ForwardPath string
}

func (Pointer) Resolve

func (p Pointer) Resolve(box string, path string) (file.File, error)

type WalkFunc

type WalkFunc = packd.WalkFunc