distribution/docs/client/transport/http_reader.go
Derek McGowan 7e4d5eafae Update transport package to sever distribution dependency
The transport package no longer requires importing distribution for the ReadSeekCloser, instead declares its own.
Added comments on the Authenication handler in session.
Added todo on http seek reader to highlight its lack of belonging to the client transport.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
2015-05-20 10:09:37 -07:00

172 lines
3.1 KiB
Go

package transport
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
)
// ReadSeekCloser combines io.ReadSeeker with io.Closer.
type ReadSeekCloser interface {
io.ReadSeeker
io.Closer
}
// NewHTTPReadSeeker handles reading from an HTTP endpoint using a GET
// request. When seeking and starting a read from a non-zero offset
// the a "Range" header will be added which sets the offset.
// TODO(dmcgowan): Move this into a separate utility package
func NewHTTPReadSeeker(client *http.Client, url string, size int64) 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
}