iohelper

Documentation

Index

• Variables
• func CheckBytesToRead(fd uintptr) (int, error)
• func CopyDir(src string, dst string) (err error)
• func CopyFile(src, dst string) (err error)
• func CreateSeekRestore(s io.Seeker) (func() (int64, error), error)
• func IsDeadlineExceeded(err error) bool
• func Pipe() (io.ReadCloser, io.WriteCloser)
• func ReadInputLine(r io.Reader, buf []byte) ([]byte, error)
• func TempFilename(dir, pattern string) (string, error)
• func WriteFile(file string, data []byte, perm os.FileMode, overwrite bool) (undo func() error, _ error)
• type BufferredReaderAt
  • func NewBufferedReaderAt(r io.Reader) *BufferredReaderAt
  • func (s *BufferredReaderAt) ReadAt(p []byte, off int64) (n int, err error)
  • func (s *BufferredReaderAt) Size() int64
• type ChunkedWriter
  • func NewChunkedWriter(chunkSize int, underlay io.Writer, doBeforeEachChunkWriting func() error, ...) *ChunkedWriter
  • func (cw *ChunkedWriter) Remainder() int
  • func (cw *ChunkedWriter) Write(p []byte) (wrote int, err error)
• type CustomReadCloser
  • func NewCustomReadCloser(r io.Reader, fClose func() error) *CustomReadCloser
  • func (c *CustomReadCloser) Close() error
• type CustomWriteCloser
  • func NewCustomWriteCloser(w io.Writer, fClose func() error) *CustomWriteCloser
  • func (c *CustomWriteCloser) Close() error
• type DevNull
  • func NewDevNull() DevNull
  • func (d DevNull) Close() error
  • func (d DevNull) Read(p []byte) (int, error)
  • func (d DevNull) Write(p []byte) (int, error)
  • func (d DevNull) WriteString(s string) (int, error)
• type FilteredReader
  • func NewFilteredReader(underlay io.Reader, filter func(p []byte) int) FilteredReader
  • func (fr FilteredReader) Read(p []byte) (n int, err error)
• type LazyAutoCloseReader
  • func (l *LazyAutoCloseReader) Read(p []byte) (ret int, err error)
• type SizedReaderAt
• type StringWriter
  • func (s StringWriter) WriteString(x string) (int, error)
• type TimeoutReader
  • func NewTimeoutReader(r io.Reader) *TimeoutReader
  • func (t *TimeoutReader) Error() error
  • func (t *TimeoutReader) FallbackReading(stopSig <-chan struct{})
  • func (t *TimeoutReader) Read(maxWait time.Duration, p []byte) (data []byte, shouldCopy bool, err error)
  • func (t *TimeoutReader) WaitForData(cancel <-chan struct{}) bool

Variables

var ErrDeadlineExceeded error

ErrDeadlineExceeded is the export of internal/poll.ErrDeadlineExceeded which is the same as os.ErrDeadlineExceeded in go1.15 and onwards

Functions

func CheckBytesToRead

func CheckBytesToRead(fd uintptr) (int, error)

CheckBytesToRead calls ioctl(fd, FIONREAD) to check ready data size of fd

func CopyDir

func CopyDir(src string, dst string) (err error)

CopyDir recursively copies a directory tree, attempting to preserve permissions. Source directory must exist, destination directory must *not* exist. Symlinks are ignored and skipped.

func CopyFile

func CopyFile(src, dst string) (err error)

CopyFile copies the contents of the file named src to the file named by dst. The file will be created if it does not already exist. If the destination file exists, all it's contents will be replaced by the contents of the source file. The file mode will be copied from the source and the copied data is synced/flushed to stable storage.

func CreateSeekRestore

func CreateSeekRestore(s io.Seeker) (func() (int64, error), error)

CreateSeekRestore creates a function to seek back to the current position.

func IsDeadlineExceeded

func IsDeadlineExceeded(err error) bool

func Pipe

func Pipe() (io.ReadCloser, io.WriteCloser)

Pipe returns io.Pipe if os.Pipe returned error

func ReadInputLine

func ReadInputLine(r io.Reader, buf []byte) ([]byte, error)

ReadInputLine reads and returns an input line from the Reader r, it returns io.ErrShortBuffer when there is more data to read but the provided buffer buf already filled up.

based on golang.org/x/term/terminal.go#readPasswordLine

func TempFilename

func TempFilename(dir, pattern string) (string, error)

func WriteFile

func WriteFile(file string, data []byte, perm os.FileMode, overwrite bool) (undo func() error, _ error)

WriteFile write data to target file

Types

type BufferredReaderAt

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

BufferredReaderAt

func NewBufferedReaderAt

func NewBufferedReaderAt(r io.Reader) *BufferredReaderAt

func (*BufferredReaderAt) ReadAt

func (s *BufferredReaderAt) ReadAt(p []byte, off int64) (n int, err error)

ReadAt implements io.ReaderAt.

func (*BufferredReaderAt) Size

func (s *BufferredReaderAt) Size() int64

Size implements SizedReaderAt.

type ChunkedWriter

type ChunkedWriter struct {
	ChunkSize int

	BeforeEachChunkWriting func() error
	AfterEachChunkWrote    func() error

	Underlay io.Writer
	// contains filtered or unexported fields
}

ChunkedWriter

func NewChunkedWriter

func NewChunkedWriter(
	chunkSize int,
	underlay io.Writer,
	doBeforeEachChunkWriting func() error,
	doAfterEachChunkWrote func() error,
) *ChunkedWriter

NewChunkedWriter returns a new ChunkedWriter.

func (*ChunkedWriter) Remainder

func (cw *ChunkedWriter) Remainder() int

Remainder

func (*ChunkedWriter) Write

func (cw *ChunkedWriter) Write(p []byte) (wrote int, err error)

type CustomReadCloser

type CustomReadCloser struct {
	io.Reader
	CloseFunc func() error
}

CustomReadCloser

func NewCustomReadCloser

func NewCustomReadCloser(r io.Reader, fClose func() error) *CustomReadCloser

NewCustomReadCloser returns a new CustomReadCloser with non-nil CloseFunc

func (*CustomReadCloser) Close

func (c *CustomReadCloser) Close() error

Close implements io.Closer.

type CustomWriteCloser

type CustomWriteCloser struct {
	io.Writer
	CloseFunc func() error
}

CustomWriteCloser

func NewCustomWriteCloser

func NewCustomWriteCloser(w io.Writer, fClose func() error) *CustomWriteCloser

NewCustomWriteCloser returns a new CustomWriteCloser with non-nil CloseFunc.

func (*CustomWriteCloser) Close

func (c *CustomWriteCloser) Close() error

Close implements io.Closer.

type DevNull

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

func NewDevNull

func NewDevNull() DevNull

func (DevNull) Close

func (d DevNull) Close() error

func (DevNull) Read

func (d DevNull) Read(p []byte) (int, error)

func (DevNull) Write

func (d DevNull) Write(p []byte) (int, error)

func (DevNull) WriteString

func (d DevNull) WriteString(s string) (int, error)

type FilteredReader

type FilteredReader struct {
	Underlay io.Reader

	// FilterFunc called on each p just read, it should update the p and
	// return the new size of p (MUST be less than len(p)).
	FilterFunc func(p []byte) int
}

FilteredReader

func NewFilteredReader

func NewFilteredReader(
	underlay io.Reader,
	filter func(p []byte) int,
) FilteredReader

func (FilteredReader) Read

func (fr FilteredReader) Read(p []byte) (n int, err error)

Read implements io.Reader.

type LazyAutoCloseReader

type LazyAutoCloseReader struct {
	Open func() (io.Reader, error)
	// contains filtered or unexported fields
}

LazyAutoCloseReader open underlay stream on first read call, closes the opened stream on error.

func (*LazyAutoCloseReader) Read

func (l *LazyAutoCloseReader) Read(p []byte) (ret int, err error)

type SizedReaderAt

type SizedReaderAt interface {
	Size() int64
	io.ReaderAt
}

type StringWriter

type StringWriter struct {
	io.Writer
}

StringWriter

func (StringWriter) WriteString

func (s StringWriter) WriteString(x string) (int, error)

WriteString implements io.StringWriter.

type TimeoutReader

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

TimeoutReader is a reader with read timeout support

It is designed for those want to read some data from a stream, and the size of the data is unknown, but still want to pipe data to some destination at certain interval

example use case: data streaming for shell interaction over MQTT

	when user input/output is slow, shall we send one character a time for real-time
	interaction? what if the user executed `cat some-large-file`? what if user
	was sending a large chunk of data over stdin?

	for raw tcp connection that's fine if you have configured tcp buffering correctly,
	but for packet oriented connections (in this case MQTT), send one byte per packet
	will significantly increase protocol overhead.

	with TimeoutReader we can read data generated in some interval (say 20ms), no
 real-time experience lost while still keep protocol overhead at a reasonable level

func NewTimeoutReader

func NewTimeoutReader(r io.Reader) *TimeoutReader

NewTimeoutReader creates a new idle timeout reader from a blocking reader

func (*TimeoutReader) Error

func (t *TimeoutReader) Error() error

Error returns the error happened during reading in background

func (*TimeoutReader) FallbackReading

func (t *TimeoutReader) FallbackReading(stopSig <-chan struct{})

func (*TimeoutReader) Read

func (t *TimeoutReader) Read(maxWait time.Duration, p []byte) (data []byte, shouldCopy bool, err error)

Read performs a read operation with timeout option, will block until maxWait exceeded or p is full

if the function returned because of timeout, the returned error is ErrDeadlineExceeded

func (*TimeoutReader) WaitForData

func (t *TimeoutReader) WaitForData(cancel <-chan struct{}) bool

WaitForData is a helper function used to check if there is data available in reader so we can reduce actual call of Read when the timeout is a short duration

when return value is true, you MUST call Read to read data and you can read at least one byte from the underlying reader

otherwise, false means the provided cancel has signaled or error happened, you can no longer read from the underlying reader if Error() returned non-nil value.