go/src/internal/coverage/slicewriter/slicewriter.go

type WriteSeeker …

func (sws *WriteSeeker) Write(p []byte) (n int, err error) { … }

// Seek repositions the read/write position of the WriteSeeker within
// its internally maintained slice. Note that it is not possible to
// expand the size of the slice using SEEK_SET; trying to seek outside
// the slice will result in an error.
func (sws *WriteSeeker) Seek(offset int64, whence int) (int64, error) { … }

// BytesWritten returns the underlying byte slice for the WriteSeeker,
// containing the data written to it via Write/Seek calls.
func (sws *WriteSeeker) BytesWritten() []byte { … }

func (sws *WriteSeeker) Read(p []byte) (n int, err error) { … }