package billy

import (
	
	
	
	
)

var (
	ErrReadOnly        = errors.New("read-only filesystem")
	ErrNotSupported    = errors.New("feature not supported")
	ErrCrossedBoundary = errors.New("chroot boundary crossed")
)
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.
type Capability uint64
WriteCapability means that the fs is writable.
ReadCapability means that the fs is readable.
ReadAndWriteCapability is the ability to open a file in read and write mode.
SeekCapability means it is able to move position inside the file.
TruncateCapability means that a file can be truncated.
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
)
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 Filesystem interface {
	Basic
	TempFile
	Dir
	Symlink
	Chroot
}
Basic abstract the basic operations in a storage-agnostic interface as an extension to the 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.
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.
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.
Stat returns a FileInfo describing the named file.
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.
Remove removes the named file or directory.
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
}
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)
}
Dir abstract the dir related operations in a storage-agnostic interface as an extension to the Basic interface.
ReadDir reads the directory named by dirname and returns a list of directory entries sorted by filename.
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
}
Symlink abstract the symlink related operations in a storage-agnostic interface as an extension to the Basic 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.
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.
Readlink returns the target path of link.
	Readlink(link string) (string, error)
}
Change abstract the FileInfo change related operations in a storage-agnostic interface as an extension to the Basic 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.
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.
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.
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
}
Chroot abstract the chroot related operations in a storage-agnostic interface as an extension to the Basic 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.
Root returns the root path of the filesystem.
	Root() string
}
File represent a file, being a subset of the os.File
Name returns the name of the file as presented to Open.
	Name() string
	io.Writer
	io.Reader
	io.ReaderAt
	io.Seeker
Lock locks the file like e.g. flock. It protects against access from other processes.
Unlock unlocks the file.
Truncate the file.
	Truncate(size int64) error
}
Capable interface can return the available features of a filesystem.
Capabilities returns the capabilities of a filesystem in bit flags.
	Capabilities() Capability
}
Capabilities returns the features supported by a filesystem. If the FS does not implement Capable interface it returns all features.
func ( Basic) Capability {
	,  := .(Capable)
	if ! {
		return DefaultCapabilities
	}

	return .Capabilities()
}
CapabilityCheck tests the filesystem for the provided capabilities and returns true in case it supports all of them.
func ( Basic,  Capability) bool {
	 := Capabilities()
	return & ==