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Implement file storage abstraction (#265)
Separate interfaces for Read and Write storage operations Introduce diskfs.OpenBackend(backend.Storage,...) to newly implemented features.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,127 @@ | ||
| package file | ||
|
|
||
| import ( | ||
| "errors" | ||
| "fmt" | ||
| "io" | ||
| "io/fs" | ||
| "os" | ||
|
|
||
| "github.com/diskfs/go-diskfs/backend" | ||
| ) | ||
|
|
||
| type rawBackend struct { | ||
| storage fs.File | ||
| readOnly bool | ||
| } | ||
|
|
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| // Create a backend.Storage from provided fs.File | ||
| func New(f fs.File, readOnly bool) backend.Storage { | ||
| return rawBackend{ | ||
| storage: f, | ||
| readOnly: readOnly, | ||
| } | ||
| } | ||
|
|
||
| // Create a backend.Storage from a path to a device | ||
| // Should pass a path to a block device e.g. /dev/sda or a path to a file /tmp/foo.img | ||
| // The provided device/file must exist at the time you call OpenFromPath() | ||
| func OpenFromPath(pathName string, readOnly bool) (backend.Storage, error) { | ||
| if pathName == "" { | ||
| return nil, errors.New("must pass device of file name") | ||
| } | ||
|
|
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| if _, err := os.Stat(pathName); os.IsNotExist(err) { | ||
| return nil, fmt.Errorf("provided device/file %s does not exist", pathName) | ||
| } | ||
|
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| openMode := os.O_RDONLY | ||
|
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| if !readOnly { | ||
| openMode |= os.O_RDWR | os.O_EXCL | ||
| } | ||
|
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| f, err := os.OpenFile(pathName, openMode, 0o600) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("could not open device %s with mode %v: %w", pathName, openMode, err) | ||
| } | ||
|
|
||
| return rawBackend{ | ||
| storage: f, | ||
| readOnly: readOnly, | ||
| }, nil | ||
| } | ||
|
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| // Create a backend.Storage from a path to an image file. | ||
| // Should pass a path to a file /tmp/foo.img | ||
| // The provided file must not exist at the time you call CreateFromPath() | ||
| func CreateFromPath(pathName string, size int64) (backend.Storage, error) { | ||
| if pathName == "" { | ||
| return nil, errors.New("must pass device name") | ||
| } | ||
| if size <= 0 { | ||
| return nil, errors.New("must pass valid device size to create") | ||
| } | ||
| f, err := os.OpenFile(pathName, os.O_RDWR|os.O_EXCL|os.O_CREATE, 0o666) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("could not create device %s: %w", pathName, err) | ||
| } | ||
| err = os.Truncate(pathName, size) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("could not expand device %s to size %d: %w", pathName, size, err) | ||
| } | ||
|
|
||
| return rawBackend{ | ||
| storage: f, | ||
| readOnly: false, | ||
| }, nil | ||
| } | ||
|
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| // backend.Storage interface guard | ||
| var _ backend.Storage = (*rawBackend)(nil) | ||
|
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| // OS-specific file for ioctl calls via fd | ||
| func (f rawBackend) Sys() (*os.File, error) { | ||
| if osFile, ok := f.storage.(*os.File); ok { | ||
| return osFile, nil | ||
| } | ||
| return nil, backend.ErrNotSuitable | ||
| } | ||
|
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| // file for read-write operations | ||
| func (f rawBackend) Writable() (backend.WritableFile, error) { | ||
| if rwFile, ok := f.storage.(backend.WritableFile); ok { | ||
| if !f.readOnly { | ||
| return rwFile, nil | ||
| } | ||
|
|
||
| return nil, backend.ErrIncorrectOpenMode | ||
| } | ||
| return nil, backend.ErrNotSuitable | ||
| } | ||
|
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| func (f rawBackend) Stat() (fs.FileInfo, error) { | ||
| return f.storage.Stat() | ||
| } | ||
|
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| func (f rawBackend) Read(b []byte) (int, error) { | ||
| return f.storage.Read(b) | ||
| } | ||
|
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| func (f rawBackend) Close() error { | ||
| return f.storage.Close() | ||
| } | ||
|
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| func (f rawBackend) ReadAt(p []byte, off int64) (n int, err error) { | ||
| if readerAt, ok := f.storage.(io.ReaderAt); ok { | ||
| return readerAt.ReadAt(p, off) | ||
| } | ||
| return -1, backend.ErrNotSuitable | ||
| } | ||
|
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| func (f rawBackend) Seek(offset int64, whence int) (int64, error) { | ||
| if seeker, ok := f.storage.(io.Seeker); ok { | ||
| return seeker.Seek(offset, whence) | ||
| } | ||
| return -1, backend.ErrNotSuitable | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,33 @@ | ||
| package backend | ||
|
|
||
| import ( | ||
| "errors" | ||
| "io" | ||
| "io/fs" | ||
| "os" | ||
| ) | ||
|
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||
| var ( | ||
| ErrIncorrectOpenMode = errors.New("disk file or device not open for write") | ||
| ErrNotSuitable = errors.New("backing file is not suitable") | ||
| ) | ||
|
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| type File interface { | ||
| fs.File | ||
| io.ReaderAt | ||
| io.Seeker | ||
| io.Closer | ||
| } | ||
|
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| type WritableFile interface { | ||
| File | ||
| io.WriterAt | ||
| } | ||
|
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| type Storage interface { | ||
| File | ||
| // OS-specific file for ioctl calls via fd | ||
| Sys() (*os.File, error) | ||
| // file for read-write operations | ||
| Writable() (WritableFile, error) | ||
| } |
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