mirror of https://github.com/spf13/afero.git
272 lines
8.7 KiB
Markdown
272 lines
8.7 KiB
Markdown
|
||
|
||
A FileSystem Abstraction System for Go
|
||
|
||
[](https://travis-ci.org/spf13/afero) [](https://ci.appveyor.com/project/mbertschler/afero) [](https://godoc.org/github.com/spf13/afero)
|
||
|
||
# Overview
|
||
|
||
Afero is an filesystem framework providing a simple, uniform and universal API
|
||
interacting with any filesystem, as an abstraction layer providing interfaces,
|
||
types and methods. Afero has an exceptionally clean interface and simple design
|
||
without needless constructors or initialization methods.
|
||
|
||
Afero is also a library providing a base set of interoperable backend
|
||
filesystems that make it easy to work with afero while retaining all the power
|
||
and benefit of the os and ioutil packages.
|
||
|
||
Afero provides significant improvements over using the os package alone, most
|
||
notably the ability to create mock and testing filesystems without relying on the disk.
|
||
|
||
It is suitable for use in a any situation where you would consider using the OS
|
||
package as it provides an additional abstraction that makes it easy to use a
|
||
memory backed file system during testing. It also adds support for the http
|
||
filesystem for full interoperability.
|
||
|
||
|
||
## Afero Features
|
||
|
||
* A single consistent API for accessing a variety of filesystems
|
||
* Interoperation between a variety of file system types
|
||
* A set of interfaces to encourage and enforce interoperability between backends
|
||
* An atomic cross platform memory backed file system
|
||
* Support for compositional file systems by joining various different file systems (see httpFs)
|
||
|
||
|
||
# Using Afero
|
||
|
||
Afero is easy to use and easier to adopt.
|
||
|
||
A few different ways you could use Afero:
|
||
|
||
* Use the interfaces alone to define you own file system.
|
||
* Wrap for the OS packages.
|
||
* Define different filesystems for different parts of your application.
|
||
* Use Afero for mock filesystems while testing
|
||
|
||
## Step 1: Install Afero
|
||
|
||
First use go get to install the latest version of the library.
|
||
|
||
$ go get github.com/spf13/afero
|
||
|
||
Next include Afero in your application.
|
||
```go
|
||
import "github.com/spf13/afero"
|
||
```
|
||
|
||
## Step 2: Declare a backend
|
||
|
||
First define a package variable and set it to a pointer to a filesystem.
|
||
```go
|
||
var AppFs afero.Fs = &afero.MemMapFs{}
|
||
|
||
or
|
||
|
||
var AppFs afero.Fs = &afero.OsFs{}
|
||
```
|
||
It is important to note that if you repeat the composite literal you
|
||
will be using a completely new and isolated filesystem. In the case of
|
||
OsFs it will still use the same underlying filesystem but will reduce
|
||
the ability to drop in other filesystems as desired.
|
||
|
||
## Step 3: Use it like you would the OS package
|
||
|
||
Throughout your application use any function and method like you normally
|
||
would.
|
||
|
||
So if my application before had:
|
||
```go
|
||
os.Open('/tmp/foo')
|
||
```
|
||
We would replace it with a call to `AppFs.Open('/tmp/foo')`.
|
||
|
||
`AppFs` being the variable we defined above.
|
||
|
||
|
||
## List of all available functions
|
||
|
||
File System Methods Available:
|
||
```go
|
||
Chmod(name string, mode os.FileMode) : error
|
||
Chtimes(name string, atime time.Time, mtime time.Time) : error
|
||
Create(name string) : File, error
|
||
Mkdir(name string, perm os.FileMode) : error
|
||
MkdirAll(path string, perm os.FileMode) : error
|
||
Name() : string
|
||
Open(name string) : File, error
|
||
OpenFile(name string, flag int, perm os.FileMode) : File, error
|
||
Remove(name string) : error
|
||
RemoveAll(path string) : error
|
||
Rename(oldname, newname string) : error
|
||
Stat(name string) : os.FileInfo, error
|
||
```
|
||
File Interfaces and Methods Available:
|
||
```go
|
||
io.Closer
|
||
io.Reader
|
||
io.ReaderAt
|
||
io.Seeker
|
||
io.Writer
|
||
io.WriterAt
|
||
|
||
Name() : string
|
||
Readdir(count int) : []os.FileInfo, error
|
||
Readdirnames(n int) : []string, error
|
||
Stat() : os.FileInfo, error
|
||
Sync() : error
|
||
Truncate(size int64) : error
|
||
WriteString(s string) : ret int, err error
|
||
```
|
||
In some applications it may make sense to define a new package that
|
||
simply exports the file system variable for easy access from anywhere.
|
||
|
||
## Using Afero for Testing
|
||
|
||
There is a large benefit to using a mock filesystem for testing. It has a
|
||
completely blank state every time it is initialized and can be easily
|
||
reproducible regardless of OS. You could create files to your heart’s content
|
||
and the file access would be fast while also saving you from all the annoying
|
||
issues with deleting temporary files, Windows file locking, etc. The MemMapFs
|
||
backend is perfect for testing.
|
||
|
||
* Much faster than performing I/O operations on disk
|
||
* Avoid security issues and permissions
|
||
* Far more control. 'rm -rf /' with confidence
|
||
* Test setup is far more easier to do
|
||
* No test cleanup needed
|
||
|
||
One way to accomplish this is to define a variable as mentioned above.
|
||
In your application this will be set to &afero.OsFs{} during testing you
|
||
can set it to &afero.MemMapFs{}.
|
||
|
||
It wouldn't be uncommon to have each test initialize a blank slate memory
|
||
backend. To do this I would define my `appFS = &afero.OsFs{}` somewhere
|
||
appropriate in my application code. This approach ensures that Tests are order
|
||
independent, with no test relying on the state left by an earlier test.
|
||
|
||
Then in my tests I would initialize a new MemMapFs for each test:
|
||
```go
|
||
func TestExist(t *testing.T) {
|
||
appFS = &afero.MemMapFs{}
|
||
// create test files and directories
|
||
appFS.MkdirAll("src/a", 0755))
|
||
appFS.WriteFile("src/a/b", []byte("file b"), 0644)
|
||
appFS.WriteFile("src/c", []byte("file c"), 0644)
|
||
testExistence("src/c", true, t)
|
||
}
|
||
|
||
func testExistence(name string, e bool, t *testing.T) {
|
||
_, err := appFS.Stat(name)
|
||
if os.IsNotExist(err) {
|
||
if e {
|
||
t.Errorf("file \"%s\" does not exist.\n", name)
|
||
}
|
||
} else if err != nil {
|
||
panic(err)
|
||
} else {
|
||
if !e {
|
||
t.Errorf("file \"%s\" exists.\n", name)
|
||
}
|
||
}
|
||
}
|
||
```
|
||
|
||
## Using Afero with Http
|
||
|
||
Afero provides an http compatible backend which can wrap any of the existing
|
||
backends.
|
||
|
||
The Http package requires a slightly specific version of Open which
|
||
returns an http.File type.
|
||
|
||
Afero provides an httpFs file system which satisfies this requirement.
|
||
Any Afero FileSystem can be used as an httpFs.
|
||
```go
|
||
httpFs := &afero.HttpFs{SourceFs: <ExistingFS>}
|
||
fileserver := http.FileServer(httpFs.Dir(<PATH>)))
|
||
http.Handle("/", fileserver)
|
||
```
|
||
# Available Backends
|
||
|
||
## OsFs
|
||
|
||
The first is simply a wrapper around the native OS calls. This makes it
|
||
very easy to use as all of the calls are the same as the existing OS
|
||
calls. It also makes it trivial to have your code use the OS during
|
||
operation and a mock filesystem during testing or as needed.
|
||
|
||
## MemMapFs
|
||
|
||
Afero also provides a fully atomic memory backed filesystem perfect for use in
|
||
mocking and to speed up unnecessary disk io when persistence isn’t
|
||
necessary. It is fully concurrent and will work within go routines
|
||
safely.
|
||
|
||
### InMemoryFile
|
||
|
||
As part of MemMapFs, Afero also provides an atomic, fully concurrent memory
|
||
backed file implementation. This can be used in other memory backed file
|
||
systems with ease. Plans are to add a radix tree memory stored file
|
||
system using InMemoryFile.
|
||
|
||
## Desired/possible backends
|
||
|
||
The following is a short list of possible backends we hope someone will
|
||
implement:
|
||
|
||
* SSH/SCP
|
||
* ZIP
|
||
* TAR
|
||
* S3
|
||
* Mem buffering to disk/network
|
||
* BasePath (where all paths are relative to a fixed basepath)
|
||
|
||
# About the project
|
||
|
||
## The name
|
||
|
||
Initially this project was called fs. Unfortunately as I used it, the
|
||
name proved confusing, there were too many fs’. In looking for
|
||
alternatives I looked up the word 'abstract' in a variety of different
|
||
languages. Afero is the Greek word for abstract and it seemed to be a
|
||
fitting name for the project. It also means ‘to do’ or ‘thing’ in
|
||
Esperanto which is also fitting.
|
||
|
||
## Release Notes
|
||
|
||
* **0.9.0** 2015.11.05
|
||
* New Walk function similar to filepath.Walk
|
||
* MemMapFs.OpenFile handles O_CREATE, O_APPEND, O_TRUNC
|
||
* MemMapFs.Remove now really deletes the file
|
||
* InMemoryFile.Readdir and Readdirnames work correctly
|
||
* InMemoryFile functions lock it for concurrent access
|
||
* Test suite improvements
|
||
* **0.8.0** 2014.10.28
|
||
* First public version
|
||
* Interfaces feel ready for people to build using
|
||
* Interfaces satisfy all known uses
|
||
* MemMapFs passes the majority of the OS test suite
|
||
* OsFs passes the majority of the OS test suite
|
||
|
||
## Contributing
|
||
|
||
1. Fork it
|
||
2. Create your feature branch (`git checkout -b my-new-feature`)
|
||
3. Commit your changes (`git commit -am 'Add some feature'`)
|
||
4. Push to the branch (`git push origin my-new-feature`)
|
||
5. Create new Pull Request
|
||
|
||
## Contributors
|
||
|
||
Names in no particular order:
|
||
|
||
* [spf13](https://github.com/spf13)
|
||
* [jaqx0r](https://github.com/jaqx0r)
|
||
* [mbertschler](https://github.com/mbertschler)
|
||
|
||
## License
|
||
|
||
Afero is released under the Apache 2.0 license. See
|
||
[LICENSE.txt](https://github.com/spf13/afero/blob/master/LICENSE.txt)
|