make spartan.Client.RoundTrip match the API of other clients.

- Request.Meta is already used as an *io.LimitedReader in spartan
  servers, so by following this convention the RoundTrip method doesn't
  need anything more than the *Request.
- Make a new public method for setting the body on a spartan request.

2 files changed, 27 insertions, 9 deletions

diff --git a/spartan/client.go b/spartan/client.go
index e571c14..40c9dd6 100644
--- a/spartan/client.go
+++ b/spartan/client.go
@@ -18,7 +18,7 @@ import (
 type Client struct{}
 
 // RoundTrip sends a single spartan request and returns its response.
-func (c Client) RoundTrip(request *sr.Request, body io.Reader) (*sr.Response, error) {
+func (c Client) RoundTrip(request *sr.Request) (*sr.Response, error) {
 	if request.Scheme != "spartan" && request.Scheme != "" {
 		return nil, errors.New("non-spartan protocols not supported")
 	}
@@ -38,20 +38,17 @@ func (c Client) RoundTrip(request *sr.Request, body io.Reader) (*sr.Response, er
 
 	request.RemoteAddr = conn.RemoteAddr()
 
-	var bodyBytes []byte = nil
-	if body != nil {
-		bodyBytes, err = io.ReadAll(body)
-		if err != nil {
-			return nil, err
-		}
+	rdr, ok := request.Meta.(*io.LimitedReader)
+	if !ok {
+		return nil, errors.New("request body must be an *io.LimitedReader")
 	}
 
-	requestLine := host + " " + request.EscapedPath() + " " + strconv.Itoa(len(bodyBytes)) + "\r\n"
+	requestLine := host + " " + request.EscapedPath() + " " + strconv.Itoa(int(rdr.N)) + "\r\n"
 
 	if _, err := conn.Write([]byte(requestLine)); err != nil {
 		return nil, err
 	}
-	if _, err := conn.Write(bodyBytes); err != nil {
+	if _, err := io.Copy(conn, rdr); err != nil {
 		return nil, err
 	}
 
diff --git a/spartan/request.go b/spartan/request.go
index a9b2815..c056af0 100644
--- a/spartan/request.go
+++ b/spartan/request.go
@@ -2,6 +2,7 @@ package spartan
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"io"
 	"net/url"
@@ -80,3 +81,23 @@ func GetRequestBody(request *sr.Request) io.Reader {
 	}
 	return nil
 }
+
+// SetRequestBody adds an io.Reader as a request body.
+//
+// It is for use in clients, preparing the request to be sent.
+//
+// This function will read the entire contents into memory unless
+// the reader is already an *io.LimitedReader.
+func SetRequestBody(request *sr.Request, body io.Reader) error {
+	if rdr, ok := body.(*io.LimitedReader); ok {
+		request.Meta = rdr
+		return nil
+	}
+
+	buf, err := io.ReadAll(body)
+	if err != nil {
+		return err
+	}
+	request.Meta = io.LimitReader(bytes.NewBuffer(buf), int64(len(buf)))
+	return nil
+}