I just ran into this as well, when buffering an io.ReadSeeker such as os.File it would be useful to have a bufio.ReadSeeker. I could work around it by calling Seek on the source os.File and using bufio.Reader.Reset(...) but this is wasteful when seeked data is already buffered
On Thursday, May 2, 2013 at 7:15:52 AM UTC-7, Ingo Oeser wrote: > > Hi there, > > is there any reason the in-memory streams bytes.Buffer and bufio.Reader > support no Seek()? > > Just wondered about it, because it would be very handy for unit tests and > benchmarks mocking out file system accesses. > > So I did sth. like this to test it: > > > http://play.golang.org/p/8SjYn-cisj > > package main > > import ( > "bytes" > "fmt" > "io" > "os" > ) > > type SeekingBuffer struct { > b []byte > buffer *bytes.Buffer > offset int64 > size int64 > } > > func NewSeekingBuffer(b []byte) *SeekingBuffer { > if b == nil { > return nil > } > return &SeekingBuffer{ > b: b, > buffer: bytes.NewBuffer(b), > offset: 0, > } > } > > func (fb *SeekingBuffer) Read(p []byte) (n int, err error) { > n, err = fb.buffer.Read(p) > fb.offset += int64(n) > return n, err > } > > func (fb *SeekingBuffer) Seek(offset int64, whence int) (ret int64, err > error) { > var newoffset int64 > switch whence { > case 0: > newoffset = offset > case 1: > newoffset = fb.offset + offset > case 2: > newoffset = int64(len(fb.b)) - offset > } > if newoffset == fb.offset { > return newoffset, nil > } > fb.buffer = bytes.NewBuffer(fb.b[newoffset:]) > fb.offset = newoffset > return fb.offset, nil > } > > func main() { > fb := NewSeekingBuffer([]byte("Hello, playground")) > pos, err := fb.Seek(0, 0) > fmt.Println("pos = ", pos, ", error = ", err) > pos, err = fb.Seek(7, 0) > fmt.Println("pos = ", pos, ", error = ", err) > io.Copy(os.Stdout, fb) > > } > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
