billy

README

go-billy

The missing interface filesystem abstraction for Go. Billy implements an interface based on the os standard library, allowing to develop applications without dependency on the underlying storage. Makes it virtually free to implement mocks and testing over filesystem operations.

Billy was born as part of go-git/go-git project.

Installation

import "github.com/go-git/go-billy/v5" // with go modules enabled (GO111MODULE=on or outside GOPATH)
import "github.com/go-git/go-billy" // with go modules disabled

Usage

Billy exposes filesystems using the Filesystem interface. Each filesystem implementation gives you a New method, whose arguments depend on the implementation itself, that returns a new Filesystem.

The following example caches in memory all readable files in a directory from any billy's filesystem implementation.

func LoadToMemory(origin billy.Filesystem, path string) (*memory.Memory, error) {
	memory := memory.New()

	files, err := origin.ReadDir("/")
	if err != nil {
		return nil, err
	}

	for _, file := range files {
		if file.IsDir() {
			continue
		}

		src, err := origin.Open(file.Name())
		if err != nil {
			return nil, err
		}

		dst, err := memory.Create(file.Name())
		if err != nil {
			return nil, err
		}

		if _, err = io.Copy(dst, src); err != nil {
			return nil, err
		}

		if err := dst.Close(); err != nil {
			return nil, err
		}

		if err := src.Close(); err != nil {
			return nil, err
		}
	}

	return memory, nil
}

Why billy?

The library billy deals with storage systems and Billy is the name of a well-known, IKEA bookcase. That's it.

License

Apache License Version 2.0, see LICENSE

Documentation

Index

• Variables
• func CapabilityCheck(fs Basic, capabilities Capability) bool
• type Basic
• type Capability
  • func Capabilities(fs Basic) Capability
• type Capable
• type Change
• type Chroot
• type Dir
• type File
• type Filesystem
• type Symlink
• type TempFile

Variables

var (
	ErrReadOnly        = errors.New("read-only filesystem")
	ErrNotSupported    = errors.New("feature not supported")
	ErrCrossedBoundary = errors.New("chroot boundary crossed")
)

Functions

func CapabilityCheck

func CapabilityCheck(fs Basic, capabilities Capability) bool

CapabilityCheck tests the filesystem for the provided capabilities and returns true in case it supports all of them.

Types

type Basic

type Basic interface {
	// Create creates the named file with mode 0666 (before umask), truncating
	// it if it already exists. If successful, methods on the returned File can
	// be used for I/O; the associated file descriptor has mode O_RDWR.
	Create(filename string) (File, error)
	// Open opens the named file for reading. If successful, methods on the
	// returned file can be used for reading; the associated file descriptor has
	// mode O_RDONLY.
	Open(filename string) (File, error)
	// OpenFile is the generalized open call; most users will use Open or Create
	// instead. It opens the named file with specified flag (O_RDONLY etc.) and
	// perm, (0666 etc.) if applicable. If successful, methods on the returned
	// File can be used for I/O.
	OpenFile(filename string, flag int, perm os.FileMode) (File, error)
	// Stat returns a FileInfo describing the named file.
	Stat(filename string) (os.FileInfo, error)
	// Rename renames (moves) oldpath to newpath. If newpath already exists and
	// is not a directory, Rename replaces it. OS-specific restrictions may
	// apply when oldpath and newpath are in different directories.
	Rename(oldpath, newpath string) error
	// Remove removes the named file or directory.
	Remove(filename string) error
	// Join joins any number of path elements into a single path, adding a
	// Separator if necessary. Join calls filepath.Clean on the result; in
	// particular, all empty strings are ignored. On Windows, the result is a
	// UNC path if and only if the first path element is a UNC path.
	Join(elem ...string) string
}

Basic abstract the basic operations in a storage-agnostic interface as an extension to the Basic interface.

type Capability

type Capability uint64

Capability holds the supported features of a billy filesystem. This does not mean that the capability has to be supported by the underlying storage. For example, a billy filesystem may support WriteCapability but the storage be mounted in read only mode.

const (
	// WriteCapability means that the fs is writable.
	WriteCapability Capability = 1 << iota
	// ReadCapability means that the fs is readable.
	ReadCapability
	// ReadAndWriteCapability is the ability to open a file in read and write mode.
	ReadAndWriteCapability
	// SeekCapability means it is able to move position inside the file.
	SeekCapability
	// TruncateCapability means that a file can be truncated.
	TruncateCapability
	// LockCapability is the ability to lock a file.
	LockCapability

	// DefaultCapabilities lists all capable features supported by filesystems
	// without Capability interface. This list should not be changed until a
	// major version is released.
	DefaultCapabilities Capability = WriteCapability | ReadCapability |
		ReadAndWriteCapability | SeekCapability | TruncateCapability |
		LockCapability

	// AllCapabilities lists all capable features.
	AllCapabilities Capability = WriteCapability | ReadCapability |
		ReadAndWriteCapability | SeekCapability | TruncateCapability |
		LockCapability
)

func Capabilities

func Capabilities(fs Basic) Capability

Capabilities returns the features supported by a filesystem. If the FS does not implement Capable interface it returns all features.

type Capable

type Capable interface {
	// Capabilities returns the capabilities of a filesystem in bit flags.
	Capabilities() Capability
}

Capable interface can return the available features of a filesystem.

type Change

type Change interface {
	// Chmod changes the mode of the named file to mode. If the file is a
	// symbolic link, it changes the mode of the link's target.
	Chmod(name string, mode os.FileMode) error
	// Lchown changes the numeric uid and gid of the named file. If the file is
	// a symbolic link, it changes the uid and gid of the link itself.
	Lchown(name string, uid, gid int) error
	// Chown changes the numeric uid and gid of the named file. If the file is a
	// symbolic link, it changes the uid and gid of the link's target.
	Chown(name string, uid, gid int) error
	// Chtimes changes the access and modification times of the named file,
	// similar to the Unix utime() or utimes() functions.
	//
	// The underlying filesystem may truncate or round the values to a less
	// precise time unit.
	Chtimes(name string, atime time.Time, mtime time.Time) error
}

Change abstract the FileInfo change related operations in a storage-agnostic interface as an extension to the Basic interface

type Chroot

type Chroot interface {
	// Chroot returns a new filesystem from the same type where the new root is
	// the given path. Files outside of the designated directory tree cannot be
	// accessed.
	Chroot(path string) (Filesystem, error)
	// Root returns the root path of the filesystem.
	Root() string
}

Chroot abstract the chroot related operations in a storage-agnostic interface as an extension to the Basic interface.

type Dir

type Dir interface {
	// ReadDir reads the directory named by dirname and returns a list of
	// directory entries sorted by filename.
	ReadDir(path string) ([]os.FileInfo, error)
	// MkdirAll creates a directory named path, along with any necessary
	// parents, and returns nil, or else returns an error. The permission bits
	// perm are used for all directories that MkdirAll creates. If path is/
	// already a directory, MkdirAll does nothing and returns nil.
	MkdirAll(filename string, perm os.FileMode) error
}

Dir abstract the dir related operations in a storage-agnostic interface as an extension to the Basic interface.

type File

type File interface {
	// Name returns the name of the file as presented to Open.
	Name() string
	io.Writer
	io.Reader
	io.ReaderAt
	io.Seeker
	io.Closer
	// Lock locks the file like e.g. flock. It protects against access from
	// other processes.
	Lock() error
	// Unlock unlocks the file.
	Unlock() error
	// Truncate the file.
	Truncate(size int64) error
}

File represent a file, being a subset of the os.File

type Filesystem

type Filesystem interface {
	Basic
	TempFile
	Dir
	Symlink
	Chroot
}

Filesystem abstract the operations in a storage-agnostic interface. Each method implementation mimics the behavior of the equivalent functions at the os package from the standard library.

type Symlink

type Symlink interface {
	// Lstat returns a FileInfo describing the named file. If the file is a
	// symbolic link, the returned FileInfo describes the symbolic link. Lstat
	// makes no attempt to follow the link.
	Lstat(filename string) (os.FileInfo, error)
	// Symlink creates a symbolic-link from link to target. target may be an
	// absolute or relative path, and need not refer to an existing node.
	// Parent directories of link are created as necessary.
	Symlink(target, link string) error
	// Readlink returns the target path of link.
	Readlink(link string) (string, error)
}

Symlink abstract the symlink related operations in a storage-agnostic interface as an extension to the Basic interface.

type TempFile

type TempFile interface {
	// TempFile creates a new temporary file in the directory dir with a name
	// beginning with prefix, opens the file for reading and writing, and
	// returns the resulting *os.File. If dir is the empty string, TempFile
	// uses the default directory for temporary files (see os.TempDir).
	// Multiple programs calling TempFile simultaneously will not choose the
	// same file. The caller can use f.Name() to find the pathname of the file.
	// It is the caller's responsibility to remove the file when no longer
	// needed.
	TempFile(dir, prefix string) (File, error)
}