174 lines
3.2 KiB
Go
174 lines
3.2 KiB
Go
package transport
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import (
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"bufio"
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"bytes"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"net/http"
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"os"
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)
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// ReadSeekCloser combines io.ReadSeeker with io.Closer.
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type ReadSeekCloser interface {
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io.ReadSeeker
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io.Closer
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}
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// NewHTTPReadSeeker handles reading from an HTTP endpoint using a GET
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// request. When seeking and starting a read from a non-zero offset
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// the a "Range" header will be added which sets the offset.
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// TODO(dmcgowan): Move this into a separate utility package
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func NewHTTPReadSeeker(client *http.Client, url string, size int64) ReadSeekCloser {
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return &httpReadSeeker{
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client: client,
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url: url,
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size: size,
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}
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}
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type httpReadSeeker struct {
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client *http.Client
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url string
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size int64
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rc io.ReadCloser // remote read closer
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brd *bufio.Reader // internal buffered io
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offset int64
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err error
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}
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func (hrs *httpReadSeeker) Read(p []byte) (n int, err error) {
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if hrs.err != nil {
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return 0, hrs.err
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}
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rd, err := hrs.reader()
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if err != nil {
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return 0, err
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}
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n, err = rd.Read(p)
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hrs.offset += int64(n)
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// Simulate io.EOF error if we reach filesize.
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if err == nil && hrs.offset >= hrs.size {
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err = io.EOF
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}
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return n, err
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}
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func (hrs *httpReadSeeker) Seek(offset int64, whence int) (int64, error) {
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if hrs.err != nil {
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return 0, hrs.err
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}
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var err error
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newOffset := hrs.offset
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switch whence {
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case os.SEEK_CUR:
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newOffset += int64(offset)
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case os.SEEK_END:
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newOffset = hrs.size + int64(offset)
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case os.SEEK_SET:
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newOffset = int64(offset)
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}
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if newOffset < 0 {
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err = errors.New("cannot seek to negative position")
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} else {
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if hrs.offset != newOffset {
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hrs.reset()
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}
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// No problems, set the offset.
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hrs.offset = newOffset
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}
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return hrs.offset, err
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}
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func (hrs *httpReadSeeker) Close() error {
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if hrs.err != nil {
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return hrs.err
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}
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// close and release reader chain
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if hrs.rc != nil {
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hrs.rc.Close()
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}
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hrs.rc = nil
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hrs.brd = nil
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hrs.err = errors.New("httpLayer: closed")
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return nil
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}
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func (hrs *httpReadSeeker) reset() {
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if hrs.err != nil {
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return
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}
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if hrs.rc != nil {
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hrs.rc.Close()
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hrs.rc = nil
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}
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}
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func (hrs *httpReadSeeker) reader() (io.Reader, error) {
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if hrs.err != nil {
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return nil, hrs.err
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}
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if hrs.rc != nil {
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return hrs.brd, nil
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}
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// If the offset is great than or equal to size, return a empty, noop reader.
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if hrs.offset >= hrs.size {
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return ioutil.NopCloser(bytes.NewReader([]byte{})), nil
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}
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req, err := http.NewRequest("GET", hrs.url, nil)
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if err != nil {
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return nil, err
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}
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if hrs.offset > 0 {
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// TODO(stevvooe): Get this working correctly.
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// If we are at different offset, issue a range request from there.
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req.Header.Add("Range", "1-")
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// TODO: get context in here
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// context.GetLogger(hrs.context).Infof("Range: %s", req.Header.Get("Range"))
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}
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resp, err := hrs.client.Do(req)
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if err != nil {
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return nil, err
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}
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// Normally would use client.SuccessStatus, but that would be a cyclic
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// import
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if resp.StatusCode >= 200 && resp.StatusCode <= 399 {
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hrs.rc = resp.Body
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} else {
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defer resp.Body.Close()
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return nil, fmt.Errorf("unexpected status resolving reader: %v", resp.Status)
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}
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if hrs.brd == nil {
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hrs.brd = bufio.NewReader(hrs.rc)
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} else {
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hrs.brd.Reset(hrs.rc)
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}
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return hrs.brd, nil
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}
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