Vendor dependencies for azure backend

vendor/github.com/Azure/go-autorest/autorest/retriablerequest.go

@@ -0,0 +1,73 @@
+package autorest
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"net/http"
+)
+
+// RetriableRequest provides facilities for retrying an HTTP request.
+type RetriableRequest struct {
+	req   *http.Request
+	rc    io.ReadCloser
+	br    *bytes.Reader
+	reset bool
+}
+
+// NewRetriableRequest returns a wrapper around an HTTP request that support retry logic.
+func NewRetriableRequest(req *http.Request) *RetriableRequest {
+	return &RetriableRequest{req: req}
+}
+
+// Request returns the wrapped HTTP request.
+func (rr *RetriableRequest) Request() *http.Request {
+	return rr.req
+}
+
+// Prepare signals that the request is about to be sent.
+func (rr *RetriableRequest) Prepare() (err error) {
+	// preserve the request body; this is to support retry logic as
+	// the underlying transport will always close the reqeust body
+	if rr.req.Body != nil {
+		if rr.reset {
+			if rr.rc != nil {
+				rr.req.Body = rr.rc
+			} else if rr.br != nil {
+				_, err = rr.br.Seek(0, io.SeekStart)
+			}
+			rr.reset = false
+			if err != nil {
+				return err
+			}
+		}
+		if rr.req.GetBody != nil {
+			// this will allow us to preserve the body without having to
+			// make a copy.  note we need to do this on each iteration
+			rr.rc, err = rr.req.GetBody()
+			if err != nil {
+				return err
+			}
+		} else if rr.br == nil {
+			// fall back to making a copy (only do this once)
+			b := []byte{}
+			if rr.req.ContentLength > 0 {
+				b = make([]byte, rr.req.ContentLength)
+				_, err = io.ReadFull(rr.req.Body, b)
+				if err != nil {
+					return err
+				}
+			} else {
+				b, err = ioutil.ReadAll(rr.req.Body)
+				if err != nil {
+					return err
+				}
+			}
+			rr.br = bytes.NewReader(b)
+			rr.req.Body = ioutil.NopCloser(rr.br)
+		}
+		// indicates that the request body needs to be reset
+		rr.reset = true
+	}
+	return err
+}