DataHoarder
6b3aaf7d0b
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continuous-integration/drone/push Build is passing
199 lines
3.9 KiB
Go
199 lines
3.9 KiB
Go
package main
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import (
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"errors"
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"fmt"
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"io"
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"net/http"
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"net/url"
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"runtime"
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"strconv"
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)
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const rangeReaderBufferSize = 4096
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type RangeReadSeekCloser struct {
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uri *url.URL
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size int64
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i int64
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body io.ReadCloser
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buf []byte
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ib int64
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closed bool
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}
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func NewRangeReadSeekCloser(uri string) (*RangeReadSeekCloser, error) {
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parsedUrl, err := url.Parse(uri)
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if err != nil {
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return nil, err
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}
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r := &RangeReadSeekCloser{
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uri: parsedUrl,
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buf: make([]byte, 0, rangeReaderBufferSize),
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}
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if err = r.getInformation(); err != nil {
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return nil, err
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}
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return r, nil
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}
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func (r *RangeReadSeekCloser) GetURI() string {
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return r.uri.String()
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}
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func (r *RangeReadSeekCloser) retryConnect() error {
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if r.closed {
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return errors.New("already closed")
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}
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headers := make(http.Header)
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startOffset := r.i
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expectedLength := r.size - startOffset
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headers.Set("Range", fmt.Sprintf("bytes=%d-", startOffset))
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response, err := http.DefaultClient.Do(&http.Request{
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Method: "GET",
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URL: r.uri,
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Header: headers,
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})
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if err != nil {
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return err
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}
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r.body = response.Body
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runtime.SetFinalizer(r.body, io.ReadCloser.Close)
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if response.StatusCode != http.StatusPartialContent {
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r.body.Close()
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r.body = nil
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return fmt.Errorf("response status code %d != %d", response.StatusCode, http.StatusPartialContent)
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}
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contentLength, err := strconv.ParseInt(response.Header.Get("content-length"), 10, 0)
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if err != nil {
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r.body.Close()
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r.body = nil
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return errors.New("server response does not have a valid Content-Length")
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}
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if contentLength != expectedLength {
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r.body.Close()
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r.body = nil
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return fmt.Errorf("server returned %d bytes, expected %d", contentLength, expectedLength)
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}
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return nil
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}
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func (r *RangeReadSeekCloser) Read(p []byte) (n int, err error) {
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for retry := 0; retry < 2; retry++ {
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if r.i >= r.size {
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return 0, io.EOF
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}
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if r.i >= r.ib {
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bufStart := int(r.i - r.ib)
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bufEnd := bufStart + len(p)
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if bufEnd <= len(r.buf) {
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copy(p, r.buf[bufStart:bufEnd])
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r.i += int64(len(p))
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return len(p), nil
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}
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}
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if r.body == nil {
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if err = r.retryConnect(); err != nil {
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continue
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}
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}
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data := make([]byte, rangeReaderBufferSize)
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n, err = r.body.Read(data)
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if err != nil { //detect actual eof, not a disconnection
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if err == io.EOF || err == io.ErrUnexpectedEOF {
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if r.i+int64(n) != r.size {
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continue
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}
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} else {
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continue
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}
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}
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r.buf = data[:n]
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r.ib = r.i
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readBytes := len(p)
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if n < readBytes {
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readBytes = n
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}
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copy(p[:readBytes], data[:readBytes])
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r.i += int64(readBytes)
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return readBytes, nil
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}
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return 0, errors.New("could not retry")
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}
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func (r *RangeReadSeekCloser) Seek(offset int64, whence int) (int64, error) {
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switch whence {
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case io.SeekStart:
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r.i = offset
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case io.SeekCurrent:
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r.i += offset
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case io.SeekEnd:
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//todo: maybe without -1?
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r.i = (r.size - 1) - offset
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default:
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return 0, fmt.Errorf("unknown whence %d", whence)
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}
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if r.i >= r.size {
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return r.i, io.EOF
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} else if r.i < 0 {
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return r.i, io.ErrUnexpectedEOF
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}
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if r.i < r.ib || r.i >= r.ib+int64(len(r.buf)) {
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if r.body != nil {
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r.body.Close()
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}
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r.body = nil
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}
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return r.i, nil
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}
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func (r *RangeReadSeekCloser) Close() error {
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if r.body != nil {
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r.closed = true
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defer func() {
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r.body = nil
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}()
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return r.body.Close()
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}
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return nil
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}
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func (r *RangeReadSeekCloser) getInformation() error {
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response, err := http.DefaultClient.Head(r.GetURI())
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if err != nil {
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return err
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}
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defer response.Body.Close()
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if response.StatusCode != http.StatusOK {
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return fmt.Errorf("response status code %d != %d", response.StatusCode, http.StatusOK)
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}
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if response.Header.Get("accept-ranges") != "bytes" {
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return errors.New("server does not accept Range")
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}
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if r.size, err = strconv.ParseInt(response.Header.Get("content-length"), 10, 0); err != nil {
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return errors.New("server response does not have a valid Content-Length")
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}
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return nil
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}
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