squashfs

README

squashfs (WIP)

A PURE Go library to read and write squashfs.

Currently has support for reading squashfs files and extracting files and folders.

Special thanks to https://dr-emann.github.io/squashfs/ for some VERY important information in an easy to understand format. Thanks also to distri's squashfs library as I referenced it to figure some things out (and double check others).

TODO

Limitations

This library is pure Go (including external libraries) which can cause some issues, which are listed below. Right now this library is also not feature complete, so check out the TODO list above for what I'm still planning on adding.

• No LZO compression. This is purely due to a lack of a good LZO pure golang library. If one is made, it would be a simple job to add it in.
• GZIP Compression
  • Strategies might or might not work.
  • Custom window sizes might or might not work.
• XZ Compression
  • LZMA executable filters are NOT supported.
• No Xattr parsing. This is simply because I haven't done any research on it and how to apply these in a pure go way.

Performane

This library, decompressing the Firefox AppImage and using go tests, takes about twice as long as unsquashfs on my quad core laptop. (~1 second with the library and about half a second with unsquashfs)

Documentation

Index

• Constants
• Variables
• type DirEntry
  • func (d DirEntry) File() (file *File, err error)
  • func (d DirEntry) Info() (fs.FileInfo, error)
  • func (d DirEntry) IsDir() bool
  • func (d DirEntry) Name() string
  • func (d DirEntry) Type() fs.FileMode
• type ExtractionOptions
  • func DefaultOptions() ExtractionOptions
• type FS
  • func (f FS) ExtractSymlink(folder string) error
  • func (f FS) ExtractTo(folder string) error
  • func (f FS) ExtractWithOptions(folder string, op ExtractionOptions) error
  • func (f FS) Glob(pattern string) (out []string, err error)
  • func (f FS) Open(name string) (fs.File, error)
  • func (f FS) ReadDir(name string) ([]fs.DirEntry, error)
  • func (f FS) ReadFile(name string) ([]byte, error)
  • func (f FS) Stat(name string) (fs.FileInfo, error)
  • func (f FS) Sub(dir string) (fs.FS, error)
• type File
  • func (f *File) Close() error
  • func (f File) ExtractSymlink(folder string) error
  • func (f File) ExtractTo(folder string) error
  • func (f File) ExtractWithOptions(folder string, op ExtractionOptions) error
  • func (f File) FS() (*FS, error)
  • func (f File) GetSymlinkFile() *File
  • func (f File) IsDir() bool
  • func (f File) IsRegular() bool
  • func (f File) IsSymlink() bool
  • func (f File) Read(p []byte) (int, error)
  • func (f File) ReadDir(n int) ([]fs.DirEntry, error)
  • func (f File) Stat() (fs.FileInfo, error)
  • func (f File) SymlinkPath() string
  • func (f File) WriteTo(w io.Writer) (int64, error)
• type FileInfo
  • func (f FileInfo) File() (file *File, err error)
  • func (f FileInfo) IsDir() bool
  • func (f FileInfo) ModTime() time.Time
  • func (f FileInfo) Mode() fs.FileMode
  • func (f FileInfo) Name() string
  • func (f FileInfo) Size() int64
  • func (f FileInfo) Sys() interface{}
• type Reader
  • func NewSquashfsReader(r io.ReaderAt) (*Reader, error)
  • func (r *Reader) ModTime() time.Time
• type SuperblockFlags
  • func (s *SuperblockFlags) ToUint() uint16

Constants

const (
	GzipCompression = 1 + iota
	LzmaCompression
	LzoCompression
	XzCompression
	Lz4Compression
	ZstdCompression
)

The types of compression supported by squashfs.

Variables

var DefaultFlags = SuperblockFlags{
	RemoveDuplicates: true,
	Exportable:       true,
}

DefaultFlags are the default SuperblockFlags that are used.

var (

	//ErrOptions is returned when compression options that I haven't tested is set. When this is returned, the Reader is also returned.
	ErrOptions = errors.New("possibly incompatible compressor options")
)

Types

type DirEntry

type DirEntry struct {
	// contains filtered or unexported fields
}

DirEntry is a child of a directory.

func (DirEntry) File

func (d DirEntry) File() (file *File, err error)

File creates a File from the DirEntry.

func (DirEntry) Info

func (d DirEntry) Info() (fs.FileInfo, error)

Info returns the fs.FileInfo for the given DirEntry.

func (DirEntry) IsDir

func (d DirEntry) IsDir() bool

IsDir Yep.

func (DirEntry) Name

func (d DirEntry) Name() string

Name returns the DirEntry's name

func (DirEntry) Type

func (d DirEntry) Type() fs.FileMode

Type returns the type bits of fs.FileMode of the DirEntry.

type ExtractionOptions

type ExtractionOptions struct {
	DereferenceSymlink bool        //Replace symlinks with the target file
	UnbreakSymlink     bool        //Try to make sure symlinks remain unbroken when extracted, without changing the symlink
	Verbose            bool        //Prints extra info to log on an error
	FolderPerm         fs.FileMode //The permissions used when creating the extraction folder
	// contains filtered or unexported fields
}

ExtractionOptions are available options on how to extract.

func DefaultOptions

func DefaultOptions() ExtractionOptions

DefaultOptions is the default ExtractionOptions.

type FS

type FS struct {
	// contains filtered or unexported fields
}

FS is a fs.FS representation of a squashfs directory. Implements fs.GlobFS, fs.ReadDirFS, fs.ReadFileFS, fs.StatFS, and fs.SubFS

func (FS) ExtractSymlink

func (f FS) ExtractSymlink(folder string) error

ExtractSymlink extracts the File to the folder with the DereferenceSymlink option. It extracts the directory's contents to the folder.

func (FS) ExtractTo

func (f FS) ExtractTo(folder string) error

ExtractTo extracts the File to the given folder with the default options. It extracts the directory's contents to the folder.

func (FS) ExtractWithOptions

func (f FS) ExtractWithOptions(folder string, op ExtractionOptions) error

ExtractWithOptions extracts the File to the given folder with the given ExtrationOptions. It extracts the directory's contents to the folder.

func (FS) Glob

func (f FS) Glob(pattern string) (out []string, err error)

Glob returns the name of the files at the given pattern. All paths are relative to the FS.

func (FS) Open

func (f FS) Open(name string) (fs.File, error)

Open opens the file at name. Returns a squashfs.File.

func (FS) ReadDir

func (f FS) ReadDir(name string) ([]fs.DirEntry, error)

ReadDir returns all the DirEntry returns all DirEntry's for the directory at name. If name is not a directory, returns an error.

func (FS) ReadFile

func (f FS) ReadFile(name string) ([]byte, error)

ReadFile returns the data (in []byte) for the file at name.

func (FS) Stat

func (f FS) Stat(name string) (fs.FileInfo, error)

Stat returns the fs.FileInfo for the file at name.

func (FS) Sub

func (f FS) Sub(dir string) (fs.FS, error)

Sub returns the FS at dir

type File

type File struct {
	// contains filtered or unexported fields
}

File represents a file inside a squashfs archive.

func (*File) Close

func (f *File) Close() error

Close simply nils the underlying reader. Here mostly to satisfy fs.File

func (File) ExtractSymlink

func (f File) ExtractSymlink(folder string) error

ExtractSymlink extracts the File to the folder with the DereferenceSymlink option. If the File is a directory, it instead extracts the directory's contents to the folder.

func (File) ExtractTo

func (f File) ExtractTo(folder string) error

ExtractTo extracts the File to the given folder with the default options. If the File is a directory, it instead extracts the directory's contents to the folder.

func (File) ExtractWithOptions

func (f File) ExtractWithOptions(folder string, op ExtractionOptions) error

ExtractWithOptions extracts the File to the given folder with the given ExtrationOptions. If the File is a directory, it instead extracts the directory's contents to the folder.

func (File) FS

func (f File) FS() (*FS, error)

FS returns the File as a FS.

func (File) GetSymlinkFile

func (f File) GetSymlinkFile() *File

GetSymlinkFile returns the File the symlink is pointing to. If not a symlink, or the target is unobtainable (such as it being outside the archive or it's absolute) returns nil

func (File) IsDir

func (f File) IsDir() bool

IsDir Yep.

func (File) IsRegular

func (f File) IsRegular() bool

IsRegular yep.

func (File) IsSymlink

func (f File) IsSymlink() bool

IsSymlink yep.

func (File) Read

func (f File) Read(p []byte) (int, error)

Read reads the data from the file. Only works if file is a normal file.

func (File) ReadDir

func (f File) ReadDir(n int) ([]fs.DirEntry, error)

ReadDir returns n fs.DirEntry's that's contained in the File (if it's a directory). If n <= 0 all fs.DirEntry's are returned.

func (File) Stat

func (f File) Stat() (fs.FileInfo, error)

Stat returns the File's fs.FileInfo

func (File) SymlinkPath

func (f File) SymlinkPath() string

SymlinkPath returns the symlink's target path. Is the File isn't a symlink, returns an empty string.

func (File) WriteTo

func (f File) WriteTo(w io.Writer) (int64, error)

WriteTo writes all data from the file to the writer. This is multi-threaded.

type FileInfo

type FileInfo struct {
	// contains filtered or unexported fields
}

FileInfo is a fs.FileInfo for a file.

func (FileInfo) File

func (f FileInfo) File() (file *File, err error)

File creates a File from the FileInfo. *File satisfies fs.File and fs.ReadDirFile.

func (FileInfo) IsDir

func (f FileInfo) IsDir() bool

IsDir yep.

func (FileInfo) ModTime

func (f FileInfo) ModTime() time.Time

ModTime is the last time the file was modified.

func (FileInfo) Mode

func (f FileInfo) Mode() fs.FileMode

Mode returns the fs.FileMode bits of the file.

func (FileInfo) Name

func (f FileInfo) Name() string

Name is the file's name.

func (FileInfo) Size

func (f FileInfo) Size() int64

Size is the file's size if it's a regular file. Otherwise, returns 0.

func (FileInfo) Sys

func (f FileInfo) Sys() interface{}

Sys returns the File for the FileInfo. If something goes wrong, nil is returned.

type Reader

type Reader struct {
	FS
	// contains filtered or unexported fields
}

Reader processes and reads a squashfs archive.

func NewSquashfsReader

func NewSquashfsReader(r io.ReaderAt) (*Reader, error)

NewSquashfsReader returns a new squashfs.Reader from an io.ReaderAt

func (*Reader) ModTime

func (r *Reader) ModTime() time.Time

ModTime is the last time the file was modified/created.

type SuperblockFlags

type SuperblockFlags struct {
	//If true, inodes are stored uncompressed.
	UncompressedInodes bool
	//If true, data is stored uncompressed.
	UncompressedData bool

	//If true, fragments are stored uncompressed.
	UncompressedFragments bool
	//If true, ALL data is stored in sequential data blocks instead of utilizing fragments.
	NoFragments bool
	//If true, the last block of data will always be stored as a fragment if it's less then the block size.
	AlwaysFragment bool
	//If true, duplicate files are only stored once. (Currently unsupported)
	RemoveDuplicates bool
	//If true, the export table is populated. (Currently unsupported)
	Exportable bool
	//If true, the xattr table is uncompressed. (Currently unsupported)
	UncompressedXattr bool
	//If true, the xattr table is not populated. (Currently unsupported)
	NoXattr bool

	//If true, the UID/GID table is stored uncompressed.
	UncompressedIDs bool
	// contains filtered or unexported fields
}

SuperblockFlags is the series of flags describing how a squashfs archive is packed.

func (*SuperblockFlags) ToUint

func (s *SuperblockFlags) ToUint() uint16

ToUint returns the uint16 representation of the given SuperblockFlags