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client.go
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client.go
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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
}