package transport import ( "bufio" "bytes" "errors" "fmt" "io" "io/ioutil" "net/http" "os" "github.com/docker/distribution" ) func NewHTTPReadSeeker(client *http.Client, url string, size int64) distribution.ReadSeekCloser { return &httpReadSeeker{ client: client, url: url, size: size, } } type httpReadSeeker struct { client *http.Client url string size int64 rc io.ReadCloser // remote read closer brd *bufio.Reader // internal buffered io offset int64 err error } func (hrs *httpReadSeeker) Read(p []byte) (n int, err error) { if hrs.err != nil { return 0, hrs.err } rd, err := hrs.reader() if err != nil { return 0, err } n, err = rd.Read(p) hrs.offset += int64(n) // Simulate io.EOF error if we reach filesize. if err == nil && hrs.offset >= hrs.size { err = io.EOF } return n, err } func (hrs *httpReadSeeker) Seek(offset int64, whence int) (int64, error) { if hrs.err != nil { return 0, hrs.err } var err error newOffset := hrs.offset switch whence { case os.SEEK_CUR: newOffset += int64(offset) case os.SEEK_END: newOffset = hrs.size + int64(offset) case os.SEEK_SET: newOffset = int64(offset) } if newOffset < 0 { err = errors.New("cannot seek to negative position") } else { if hrs.offset != newOffset { hrs.reset() } // No problems, set the offset. hrs.offset = newOffset } return hrs.offset, err } func (hrs *httpReadSeeker) Close() error { if hrs.err != nil { return hrs.err } // close and release reader chain if hrs.rc != nil { hrs.rc.Close() } hrs.rc = nil hrs.brd = nil hrs.err = errors.New("httpLayer: closed") return nil } func (hrs *httpReadSeeker) reset() { if hrs.err != nil { return } if hrs.rc != nil { hrs.rc.Close() hrs.rc = nil } } func (hrs *httpReadSeeker) reader() (io.Reader, error) { if hrs.err != nil { return nil, hrs.err } if hrs.rc != nil { return hrs.brd, nil } // If the offset is great than or equal to size, return a empty, noop reader. if hrs.offset >= hrs.size { return ioutil.NopCloser(bytes.NewReader([]byte{})), nil } req, err := http.NewRequest("GET", hrs.url, nil) if err != nil { return nil, err } if hrs.offset > 0 { // TODO(stevvooe): Get this working correctly. // If we are at different offset, issue a range request from there. req.Header.Add("Range", "1-") // TODO: get context in here // context.GetLogger(hrs.context).Infof("Range: %s", req.Header.Get("Range")) } resp, err := hrs.client.Do(req) if err != nil { return nil, err } switch { case resp.StatusCode == 200: hrs.rc = resp.Body default: defer resp.Body.Close() return nil, fmt.Errorf("unexpected status resolving reader: %v", resp.Status) } if hrs.brd == nil { hrs.brd = bufio.NewReader(hrs.rc) } else { hrs.brd.Reset(hrs.rc) } return hrs.brd, nil }