package webseed import ( "bytes" "context" "errors" "fmt" "io" "net/http" "github.com/anacrolix/torrent/metainfo" "github.com/anacrolix/torrent/segments" ) type RequestSpec = segments.Extent type requestPartResult struct { resp *http.Response err error } type requestPart struct { req *http.Request e segments.Extent result chan requestPartResult } type Request struct { cancel func() Result chan RequestResult } func (r Request) Cancel() { r.cancel() } type Client struct { HttpClient *http.Client Url string FileIndex segments.Index Info *metainfo.Info } type RequestResult struct { Bytes []byte Err error } func (ws *Client) NewRequest(r RequestSpec) Request { ctx, cancel := context.WithCancel(context.Background()) var requestParts []requestPart if !ws.FileIndex.Locate(r, func(i int, e segments.Extent) bool { req, err := NewRequest(ws.Url, i, ws.Info, e.Start, e.Length) if err != nil { panic(err) } req = req.WithContext(ctx) part := requestPart{ req: req, result: make(chan requestPartResult, 1), e: e, } go func() { resp, err := ws.HttpClient.Do(req) part.result <- requestPartResult{ resp: resp, err: err, } }() requestParts = append(requestParts, part) return true }) { panic("request out of file bounds") } req := Request{ cancel: cancel, Result: make(chan RequestResult, 1), } go func() { b, err := readRequestPartResponses(requestParts) req.Result <- RequestResult{ Bytes: b, Err: err, } }() return req } func recvPartResult(buf io.Writer, part requestPart) error { result := <-part.result if result.err != nil { return result.err } defer result.resp.Body.Close() switch result.resp.StatusCode { case http.StatusPartialContent: case http.StatusOK: if part.e.Start != 0 { return errors.New("got status ok but request was at offset") } default: return fmt.Errorf("unhandled response status code (%v)", result.resp.StatusCode) } copied, err := io.Copy(buf, result.resp.Body) if err != nil { return err } if copied != part.e.Length { return fmt.Errorf("got %v bytes, expected %v", copied, part.e.Length) } return nil } func readRequestPartResponses(parts []requestPart) ([]byte, error) { var buf bytes.Buffer for _, part := range parts { err := recvPartResult(&buf, part) if err != nil { return buf.Bytes(), fmt.Errorf("reading %q at %q: %w", part.req.URL, part.req.Header.Get("Range"), err) } } return buf.Bytes(), nil }