From 3546c31c2b0781daf233fa22a9fb2b8fd1cb2cbe Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Tue, 1 Mar 2016 01:13:50 +0200
Subject: [PATCH] Issue #60: skip body copying in DoTimeout. This should
 improve DoTimeout performance when dealing with big request and/or response
 bodies

---
 client.go |  6 ++++--
 http.go   | 22 ++++++++++++++++++++--
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/client.go b/client.go
index 1745e13..b48e9fa 100644
--- a/client.go
+++ b/client.go
@@ -862,7 +862,8 @@ func clientDoDeadlineFreeConn(req *Request, resp *Response, deadline time.Time,
 	// Make req and resp copies, since on timeout they no longer
 	// may be accessed.
 	reqCopy := AcquireRequest()
-	req.CopyTo(reqCopy)
+	req.copyToSkipBody(reqCopy)
+	swapRequestBody(req, reqCopy)
 	respCopy := AcquireResponse()
 
 	// Note that the request continues execution on ErrTimeout until
@@ -889,7 +890,8 @@ func clientDoDeadlineFreeConn(req *Request, resp *Response, deadline time.Time,
 	var err error
 	select {
 	case err = <-ch:
-		respCopy.CopyTo(resp)
+		respCopy.copyToSkipBody(resp)
+		swapResponseBody(resp, respCopy)
 		ReleaseResponse(respCopy)
 		ReleaseRequest(reqCopy)
 		errorChPool.Put(chv)
diff --git a/http.go b/http.go
index b2ec26d..5fc4b62 100644
--- a/http.go
+++ b/http.go
@@ -433,9 +433,13 @@ func (req *Request) ResetBody() {
 
 // CopyTo copies req contents to dst except of body stream.
 func (req *Request) CopyTo(dst *Request) {
+	req.copyToSkipBody(dst)
+	dst.body = append(dst.body[:0], req.body...)
+}
+
+func (req *Request) copyToSkipBody(dst *Request) {
 	dst.Reset()
 	req.Header.CopyTo(&dst.Header)
-	dst.body = append(dst.body[:0], req.body...)
 
 	req.uri.CopyTo(&dst.uri)
 	dst.parsedURI = req.parsedURI
@@ -449,12 +453,26 @@ func (req *Request) CopyTo(dst *Request) {
 
 // CopyTo copies resp contents to dst except of body stream.
 func (resp *Response) CopyTo(dst *Response) {
+	resp.copyToSkipBody(dst)
+	dst.body = append(dst.body[:0], resp.body...)
+}
+
+func (resp *Response) copyToSkipBody(dst *Response) {
 	dst.Reset()
 	resp.Header.CopyTo(&dst.Header)
-	dst.body = append(dst.body[:0], resp.body...)
 	dst.SkipBody = resp.SkipBody
 }
 
+func swapRequestBody(a, b *Request) {
+	a.body, b.body = b.body, a.body
+	a.bodyStream, b.bodyStream = b.bodyStream, a.bodyStream
+}
+
+func swapResponseBody(a, b *Response) {
+	a.body, b.body = b.body, a.body
+	a.bodyStream, b.bodyStream = b.bodyStream, a.bodyStream
+}
+
 // URI returns request URI
 func (req *Request) URI() *URI {
 	req.parseURI()