mirror of https://github.com/spf13/afero.git
202 lines
6.7 KiB
Markdown
202 lines
6.7 KiB
Markdown
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A FileSystem Abstraction System for Go
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[](https://travis-ci.org/spf13/afero) [](https://godoc.org/github.com/spf13/afero)
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## Overview
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Package Afero provides types and methods for interacting with the filesystem,
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as an abstraction layer.
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It provides a few implementations that are largely interoperable. One that
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uses the operating system filesystem, one that uses memory to store files
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(cross platform) and an interface that should be implemented if you want to
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provide your own filesystem.
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It is suitable for use in a any situation where you would consider using
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the OS package as it provides an additional abstraction that makes it
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easy to use a memory backed file system during testing. It also adds
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support for the http filesystem for full interoperability.
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Afero has an exceptionally clean interface and simple design without needless
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constructors or initialization methods.
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## The name
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Initially this project was called fs. Unfortunately as I used it, the
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name proved confusing, there were too many fs’. In looking for
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alternatives I looked up the word 'abstract' in a variety of different
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languages. Afero is the Greek word for abstract and it seemed to be a
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fitting name for the project. It also means ‘to do’ or ‘thing’ in
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Esperanto which is also fitting.
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## Interface
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Afero simply takes the interfaces already defined throughout the standard
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library and unifies them into a pair of interfaces that satisfy all
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known uses. One interface for a file and one for a filesystem.
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## Filesystems
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Afero additionally comes with a few filesystems and file implementations
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ready to use.
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### OsFs
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The first is simply a wrapper around the native OS calls. This makes it
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very easy to use as all of the calls are the same as the existing OS
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calls. It also makes it trivial to have your code use the OS during
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operation and a mock filesystem during testing or as needed.
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### MemMapFs
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Afero also provides a fully atomic memory backed filesystem perfect for use in
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mocking and to speed up unnecessary disk io when persistence isn’t
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necessary. It is fully concurrent and will work within go routines
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safely.
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#### InMemoryFile
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As part of MemMapFs, Afero also provides an atomic, fully concurrent memory
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backed file implementation. This can be used in other memory backed file
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systems with ease. Plans are to add a radix tree memory stored file
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system using InMemoryFile.
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## Usage
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### Installing
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Using Afero is easy. First use go get to install the latest version
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of the library.
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$ go get github.com/spf13/afero
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Next include Afero in your application.
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import "github.com/spf13/afero"
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## Using Afero
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There are a few different ways to use Afero. You could use the
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interfaces alone to define you own file system. You could use it as a
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wrapper for the OS packages. You could use it to define different
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filesystems for different parts of your application. Here we will
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demonstrate a basic usage.
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First define a package variable and set it to a pointer to a filesystem.
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var AppFs afero.Fs = &afero.MemMapFs{}
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or
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var AppFs afero.Fs = &afero.OsFs{}
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It is important to note that if you repeat the composite literal you
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will be using a completely new and isolated filesystem. In the case of
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OsFs it will still use the same underlying filesystem but will reduce
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the ability to drop in other filesystems as desired.
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Then throughout your functions and methods use the methods familiar
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already from the OS package.
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File System Methods Available:
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Chmod(name string, mode os.FileMode) : error
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Chtimes(name string, atime time.Time, mtime time.Time) : error
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Create(name string) : File, error
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Mkdir(name string, perm os.FileMode) : error
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MkdirAll(path string, perm os.FileMode) : error
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Name() : string
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Open(name string) : File, error
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OpenFile(name string, flag int, perm os.FileMode) : File, error
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Remove(name string) : error
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RemoveAll(path string) : error
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Rename(oldname, newname string) : error
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Stat(name string) : os.FileInfo, error
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File Interfaces and Methods Available:
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io.Closer
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io.Reader
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io.ReaderAt
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io.Seeker
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io.Writer
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io.WriterAt
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Name() : string
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Readdir(count int) : []os.FileInfo, error
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Readdirnames(n int) : []string, error
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Stat() : os.FileInfo, error
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Sync() : error
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Truncate(size int64) : error
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WriteString(s string) : ret int, err error
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In our case we would call `AppFs.Open()` as an example because that is how we’ve defined to
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access our filesystem.
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In some applications it may make sense to define a new package that
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simply exports the file system variable for easy access from anywhere.
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### Using a Mock Filesystem for Testing
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There is a large benefit to using a mock filesystem for testing. It has
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a completely blank state every time it is initialized and can be easily
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reproducible regardless of OS. It is also faster than disk which makes
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the tests run faster. Lastly it doesn’t require any clean up after tests
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are run.
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One way to accomplish this is to define a variable as mentioned above.
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In your application this will be set to &afero.OsFs{} during testing you
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can set it to &afero.MemMapFs{}.
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### Using with Http
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The Http package requires a slightly specific version of Open which
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returns an http.File type.
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Afero provides an httpFs file system which satisfies this requirement.
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Any Afero FileSystem can be used as an httpFs.
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httpFs := &afero.HttpFs{SourceFs: <ExistingFS>}
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fileserver := http.FileServer(httpFs.Dir(<PATH>)))
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http.Handle("/", fileserver)
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## Release Notes
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* **0.9.0** 2015.11.05
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* New Walk function similar to filepath.Walk
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* MemMapFs.OpenFile handles O_CREATE, O_APPEND, O_TRUNC
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* MemMapFs.Remove now really deletes the file
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* InMemoryFile.Readdir and Readdirnames work correctly
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* InMemoryFile functions lock it for concurrent access
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* Test suite improvements
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* **0.8.0** 2014.10.28
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* First public version
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* Interfaces feel ready for people to build using
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* Interfaces satisfy all known uses
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* MemMapFs passes the majority of the OS test suite
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* OsFs passes the majority of the OS test suite
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## Contributing
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1. Fork it
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2. Create your feature branch (`git checkout -b my-new-feature`)
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3. Commit your changes (`git commit -am 'Add some feature'`)
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4. Push to the branch (`git push origin my-new-feature`)
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5. Create new Pull Request
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## Contributors
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Names in no particular order:
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* [spf13](https://github.com/spf13)
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* [jaqx0r](https://github.com/jaqx0r)
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* [mbertschler](https://github.com/mbertschler)
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## License
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Afero is released under the Apache 2.0 license. See [LICENSE.txt](https://github.com/spf13/afero/blob/master/LICENSE.txt)
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