src/net/http/httputil/persist.go - go - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package httputil

 import (
 	"bufio"
 	"errors"
 	"io"
 	"net"
 	"net/http"
 	"net/textproto"
 	"sync"
 )

 var (
 	// Deprecated: No longer used.
 	ErrPersistEOF = &http.ProtocolError{ErrorString: "persistent connection closed"}

 	// Deprecated: No longer used.
 	ErrClosed = &http.ProtocolError{ErrorString: "connection closed by user"}

 	// Deprecated: No longer used.
 	ErrPipeline = &http.ProtocolError{ErrorString: "pipeline error"}
 )

 // This is an API usage error - the local side is closed.
 // ErrPersistEOF (above) reports that the remote side is closed.
 var errClosed = errors.New("i/o operation on closed connection")

 // ServerConn is an artifact of Go's early HTTP implementation.
 // It is low-level, old, and unused by Go's current HTTP stack.
 // We should have deleted it before Go 1.
 //
 // Deprecated: Use the Server in package net/http instead.
 type ServerConn struct {
 	mu              sync.Mutex // read-write protects the following fields
 	c               net.Conn
 	r               *bufio.Reader
 	re, we          error // read/write errors
 	lastbody        io.ReadCloser
 	nread, nwritten int
 	pipereq         map[*http.Request]uint

 	pipe textproto.Pipeline
 }

 // NewServerConn is an artifact of Go's early HTTP implementation.
 // It is low-level, old, and unused by Go's current HTTP stack.
 // We should have deleted it before Go 1.
 //
 // Deprecated: Use the Server in package net/http instead.
 func NewServerConn(c net.Conn, r *bufio.Reader) *ServerConn {
 	if r == nil {
 		r = bufio.NewReader(c)
 	}
 	return &ServerConn{c: c, r: r, pipereq: make(map[*http.Request]uint)}
 }

 // Hijack detaches the ServerConn and returns the underlying connection as well
 // as the read-side bufio which may have some left over data. Hijack may be
 // called before Read has signaled the end of the keep-alive logic. The user
 // should not call Hijack while Read or Write is in progress.
 func (sc *ServerConn) Hijack() (net.Conn, *bufio.Reader) {
 	sc.mu.Lock()
 	defer sc.mu.Unlock()
 	c := sc.c
 	r := sc.r
 	sc.c = nil
 	sc.r = nil
 	return c, r
 }

 // Close calls Hijack and then also closes the underlying connection.
 func (sc *ServerConn) Close() error {
 	c, _ := sc.Hijack()
 	if c != nil {
 		return c.Close()
 	}
 	return nil
 }

 // Read returns the next request on the wire. An ErrPersistEOF is returned if
 // it is gracefully determined that there are no more requests (e.g. after the
 // first request on an HTTP/1.0 connection, or after a Connection:close on a
 // HTTP/1.1 connection).
 func (sc *ServerConn) Read() (*http.Request, error) {
 	var req *http.Request
 	var err error

 	// Ensure ordered execution of Reads and Writes
 	id := sc.pipe.Next()
 	sc.pipe.StartRequest(id)
 	defer func() {
 		sc.pipe.EndRequest(id)
 		if req == nil {
 			sc.pipe.StartResponse(id)
 			sc.pipe.EndResponse(id)
 		} else {
 			// Remember the pipeline id of this request
 			sc.mu.Lock()
 			sc.pipereq[req] = id
 			sc.mu.Unlock()
 		}
 	}()

 	sc.mu.Lock()
 	if sc.we != nil { // no point receiving if write-side broken or closed
 		defer sc.mu.Unlock()
 		return nil, sc.we
 	}
 	if sc.re != nil {
 		defer sc.mu.Unlock()
 		return nil, sc.re
 	}
 	if sc.r == nil { // connection closed by user in the meantime
 		defer sc.mu.Unlock()
 		return nil, errClosed
 	}
 	r := sc.r
 	lastbody := sc.lastbody
 	sc.lastbody = nil
 	sc.mu.Unlock()

 	// Make sure body is fully consumed, even if user does not call body.Close
 	if lastbody != nil {
 		// body.Close is assumed to be idempotent and multiple calls to
 		// it should return the error that its first invocation
 		// returned.
 		err = lastbody.Close()
 		if err != nil {
 			sc.mu.Lock()
 			defer sc.mu.Unlock()
 			sc.re = err
 			return nil, err
 		}
 	}

 	req, err = http.ReadRequest(r)
 	sc.mu.Lock()
 	defer sc.mu.Unlock()
 	if err != nil {
 		if err == io.ErrUnexpectedEOF {
 			// A close from the opposing client is treated as a
 			// graceful close, even if there was some unparse-able
 			// data before the close.
 			sc.re = ErrPersistEOF
 			return nil, sc.re
 		} else {
 			sc.re = err
 			return req, err
 		}
 	}
 	sc.lastbody = req.Body
 	sc.nread++
 	if req.Close {
 		sc.re = ErrPersistEOF
 		return req, sc.re
 	}
 	return req, err
 }

 // Pending returns the number of unanswered requests
 // that have been received on the connection.
 func (sc *ServerConn) Pending() int {
 	sc.mu.Lock()
 	defer sc.mu.Unlock()
 	return sc.nread - sc.nwritten
 }

 // Write writes resp in response to req. To close the connection gracefully, set the
 // Response.Close field to true. Write should be considered operational until
 // it returns an error, regardless of any errors returned on the Read side.
 func (sc *ServerConn) Write(req *http.Request, resp *http.Response) error {

 	// Retrieve the pipeline ID of this request/response pair
 	sc.mu.Lock()
 	id, ok := sc.pipereq[req]
 	delete(sc.pipereq, req)
 	if !ok {
 		sc.mu.Unlock()
 		return ErrPipeline
 	}
 	sc.mu.Unlock()

 	// Ensure pipeline order
 	sc.pipe.StartResponse(id)
 	defer sc.pipe.EndResponse(id)

 	sc.mu.Lock()
 	if sc.we != nil {
 		defer sc.mu.Unlock()
 		return sc.we
 	}
 	if sc.c == nil { // connection closed by user in the meantime
 		defer sc.mu.Unlock()
 		return ErrClosed
 	}
 	c := sc.c
 	if sc.nread <= sc.nwritten {
 		defer sc.mu.Unlock()
 		return errors.New("persist server pipe count")
 	}
 	if resp.Close {
 		// After signaling a keep-alive close, any pipelined unread
 		// requests will be lost. It is up to the user to drain them
 		// before signaling.
 		sc.re = ErrPersistEOF
 	}
 	sc.mu.Unlock()

 	err := resp.Write(c)
 	sc.mu.Lock()
 	defer sc.mu.Unlock()
 	if err != nil {
 		sc.we = err
 		return err
 	}
 	sc.nwritten++

 	return nil
 }

 // ClientConn is an artifact of Go's early HTTP implementation.
 // It is low-level, old, and unused by Go's current HTTP stack.
 // We should have deleted it before Go 1.
 //
 // Deprecated: Use Client or Transport in package net/http instead.
 type ClientConn struct {
 	mu              sync.Mutex // read-write protects the following fields
 	c               net.Conn
 	r               *bufio.Reader
 	re, we          error // read/write errors
 	lastbody        io.ReadCloser
 	nread, nwritten int
 	pipereq         map[*http.Request]uint

 	pipe     textproto.Pipeline
 	writeReq func(*http.Request, io.Writer) error
 }

 // NewClientConn is an artifact of Go's early HTTP implementation.
 // It is low-level, old, and unused by Go's current HTTP stack.
 // We should have deleted it before Go 1.
 //
 // Deprecated: Use the Client or Transport in package net/http instead.
 func NewClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
 	if r == nil {
 		r = bufio.NewReader(c)
 	}
 	return &ClientConn{
 		c:        c,
 		r:        r,
 		pipereq:  make(map[*http.Request]uint),
 		writeReq: (*http.Request).Write,
 	}
 }

 // NewProxyClientConn is an artifact of Go's early HTTP implementation.
 // It is low-level, old, and unused by Go's current HTTP stack.
 // We should have deleted it before Go 1.
 //
 // Deprecated: Use the Client or Transport in package net/http instead.
 func NewProxyClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
 	cc := NewClientConn(c, r)
 	cc.writeReq = (*http.Request).WriteProxy
 	return cc
 }

 // Hijack detaches the ClientConn and returns the underlying connection as well
 // as the read-side bufio which may have some left over data. Hijack may be
 // called before the user or Read have signaled the end of the keep-alive
 // logic. The user should not call Hijack while Read or Write is in progress.
 func (cc *ClientConn) Hijack() (c net.Conn, r *bufio.Reader) {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 	c = cc.c
 	r = cc.r
 	cc.c = nil
 	cc.r = nil
 	return
 }

 // Close calls Hijack and then also closes the underlying connection.
 func (cc *ClientConn) Close() error {
 	c, _ := cc.Hijack()
 	if c != nil {
 		return c.Close()
 	}
 	return nil
 }

 // Write writes a request. An ErrPersistEOF error is returned if the connection
 // has been closed in an HTTP keep-alive sense. If req.Close equals true, the
 // keep-alive connection is logically closed after this request and the opposing
 // server is informed. An ErrUnexpectedEOF indicates the remote closed the
 // underlying TCP connection, which is usually considered as graceful close.
 func (cc *ClientConn) Write(req *http.Request) error {
 	var err error

 	// Ensure ordered execution of Writes
 	id := cc.pipe.Next()
 	cc.pipe.StartRequest(id)
 	defer func() {
 		cc.pipe.EndRequest(id)
 		if err != nil {
 			cc.pipe.StartResponse(id)
 			cc.pipe.EndResponse(id)
 		} else {
 			// Remember the pipeline id of this request
 			cc.mu.Lock()
 			cc.pipereq[req] = id
 			cc.mu.Unlock()
 		}
 	}()

 	cc.mu.Lock()
 	if cc.re != nil { // no point sending if read-side closed or broken
 		defer cc.mu.Unlock()
 		return cc.re
 	}
 	if cc.we != nil {
 		defer cc.mu.Unlock()
 		return cc.we
 	}
 	if cc.c == nil { // connection closed by user in the meantime
 		defer cc.mu.Unlock()
 		return errClosed
 	}
 	c := cc.c
 	if req.Close {
 		// We write the EOF to the write-side error, because there
 		// still might be some pipelined reads
 		cc.we = ErrPersistEOF
 	}
 	cc.mu.Unlock()

 	err = cc.writeReq(req, c)
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 	if err != nil {
 		cc.we = err
 		return err
 	}
 	cc.nwritten++

 	return nil
 }

 // Pending returns the number of unanswered requests
 // that have been sent on the connection.
 func (cc *ClientConn) Pending() int {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 	return cc.nwritten - cc.nread
 }

 // Read reads the next response from the wire. A valid response might be
 // returned together with an ErrPersistEOF, which means that the remote
 // requested that this be the last request serviced. Read can be called
 // concurrently with Write, but not with another Read.
 func (cc *ClientConn) Read(req *http.Request) (resp *http.Response, err error) {
 	// Retrieve the pipeline ID of this request/response pair
 	cc.mu.Lock()
 	id, ok := cc.pipereq[req]
 	delete(cc.pipereq, req)
 	if !ok {
 		cc.mu.Unlock()
 		return nil, ErrPipeline
 	}
 	cc.mu.Unlock()

 	// Ensure pipeline order
 	cc.pipe.StartResponse(id)
 	defer cc.pipe.EndResponse(id)

 	cc.mu.Lock()
 	if cc.re != nil {
 		defer cc.mu.Unlock()
 		return nil, cc.re
 	}
 	if cc.r == nil { // connection closed by user in the meantime
 		defer cc.mu.Unlock()
 		return nil, errClosed
 	}
 	r := cc.r
 	lastbody := cc.lastbody
 	cc.lastbody = nil
 	cc.mu.Unlock()

 	// Make sure body is fully consumed, even if user does not call body.Close
 	if lastbody != nil {
 		// body.Close is assumed to be idempotent and multiple calls to
 		// it should return the error that its first invocation
 		// returned.
 		err = lastbody.Close()
 		if err != nil {
 			cc.mu.Lock()
 			defer cc.mu.Unlock()
 			cc.re = err
 			return nil, err
 		}
 	}

 	resp, err = http.ReadResponse(r, req)
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 	if err != nil {
 		cc.re = err
 		return resp, err
 	}
 	cc.lastbody = resp.Body

 	cc.nread++

 	if resp.Close {
 		cc.re = ErrPersistEOF // don't send any more requests
 		return resp, cc.re
 	}
 	return resp, err
 }

 // Do is convenience method that writes a request and reads a response.
 func (cc *ClientConn) Do(req *http.Request) (*http.Response, error) {
 	err := cc.Write(req)
 	if err != nil {
 		return nil, err
 	}
 	return cc.Read(req)
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package httputil

	import (
	"bufio"
	"errors"
	"io"
	"net"
	"net/http"
	"net/textproto"
	"sync"
	)

	var (
	// Deprecated: No longer used.
	ErrPersistEOF = &http.ProtocolError{ErrorString: "persistent connection closed"}

	// Deprecated: No longer used.
	ErrClosed = &http.ProtocolError{ErrorString: "connection closed by user"}

	// Deprecated: No longer used.
	ErrPipeline = &http.ProtocolError{ErrorString: "pipeline error"}
	)

	// This is an API usage error - the local side is closed.
	// ErrPersistEOF (above) reports that the remote side is closed.
	var errClosed = errors.New("i/o operation on closed connection")

	// ServerConn is an artifact of Go's early HTTP implementation.
	// It is low-level, old, and unused by Go's current HTTP stack.
	// We should have deleted it before Go 1.
	//
	// Deprecated: Use the Server in package net/http instead.
	type ServerConn struct {
	mu sync.Mutex // read-write protects the following fields
	c net.Conn
	r *bufio.Reader
	re, we error // read/write errors
	lastbody io.ReadCloser
	nread, nwritten int
	pipereq map[*http.Request]uint

	pipe textproto.Pipeline
	}

	// NewServerConn is an artifact of Go's early HTTP implementation.
	// It is low-level, old, and unused by Go's current HTTP stack.
	// We should have deleted it before Go 1.
	//
	// Deprecated: Use the Server in package net/http instead.
	func NewServerConn(c net.Conn, r bufio.Reader) ServerConn {
	if r == nil {
	r = bufio.NewReader(c)
	}
	return &ServerConn{c: c, r: r, pipereq: make(map[*http.Request]uint)}
	}

	// Hijack detaches the ServerConn and returns the underlying connection as well
	// as the read-side bufio which may have some left over data. Hijack may be
	// called before Read has signaled the end of the keep-alive logic. The user
	// should not call Hijack while Read or Write is in progress.
	func (sc ServerConn) Hijack() (net.Conn, bufio.Reader) {
	sc.mu.Lock()
	defer sc.mu.Unlock()
	c := sc.c
	r := sc.r
	sc.c = nil
	sc.r = nil
	return c, r
	}

	// Close calls Hijack and then also closes the underlying connection.
	func (sc *ServerConn) Close() error {
	c, _ := sc.Hijack()
	if c != nil {
	return c.Close()
	}
	return nil
	}

	// Read returns the next request on the wire. An ErrPersistEOF is returned if
	// it is gracefully determined that there are no more requests (e.g. after the
	// first request on an HTTP/1.0 connection, or after a Connection:close on a
	// HTTP/1.1 connection).
	func (sc ServerConn) Read() (http.Request, error) {
	var req *http.Request
	var err error

	// Ensure ordered execution of Reads and Writes
	id := sc.pipe.Next()
	sc.pipe.StartRequest(id)
	defer func() {
	sc.pipe.EndRequest(id)
	if req == nil {
	sc.pipe.StartResponse(id)
	sc.pipe.EndResponse(id)
	} else {
	// Remember the pipeline id of this request
	sc.mu.Lock()
	sc.pipereq[req] = id
	sc.mu.Unlock()
	}
	}()

	sc.mu.Lock()
	if sc.we != nil { // no point receiving if write-side broken or closed
	defer sc.mu.Unlock()
	return nil, sc.we
	}
	if sc.re != nil {
	defer sc.mu.Unlock()
	return nil, sc.re
	}
	if sc.r == nil { // connection closed by user in the meantime
	defer sc.mu.Unlock()
	return nil, errClosed
	}
	r := sc.r
	lastbody := sc.lastbody
	sc.lastbody = nil
	sc.mu.Unlock()

	// Make sure body is fully consumed, even if user does not call body.Close
	if lastbody != nil {
	// body.Close is assumed to be idempotent and multiple calls to
	// it should return the error that its first invocation
	// returned.
	err = lastbody.Close()
	if err != nil {
	sc.mu.Lock()
	defer sc.mu.Unlock()
	sc.re = err
	return nil, err
	}
	}

	req, err = http.ReadRequest(r)
	sc.mu.Lock()
	defer sc.mu.Unlock()
	if err != nil {
	if err == io.ErrUnexpectedEOF {
	// A close from the opposing client is treated as a
	// graceful close, even if there was some unparse-able
	// data before the close.
	sc.re = ErrPersistEOF
	return nil, sc.re
	} else {
	sc.re = err
	return req, err
	}
	}
	sc.lastbody = req.Body
	sc.nread++
	if req.Close {
	sc.re = ErrPersistEOF
	return req, sc.re
	}
	return req, err
	}

	// Pending returns the number of unanswered requests
	// that have been received on the connection.
	func (sc *ServerConn) Pending() int {
	sc.mu.Lock()
	defer sc.mu.Unlock()
	return sc.nread - sc.nwritten
	}

	// Write writes resp in response to req. To close the connection gracefully, set the
	// Response.Close field to true. Write should be considered operational until
	// it returns an error, regardless of any errors returned on the Read side.
	func (sc ServerConn) Write(req http.Request, resp *http.Response) error {

	// Retrieve the pipeline ID of this request/response pair
	sc.mu.Lock()
	id, ok := sc.pipereq[req]
	delete(sc.pipereq, req)
	if !ok {
	sc.mu.Unlock()
	return ErrPipeline
	}
	sc.mu.Unlock()

	// Ensure pipeline order
	sc.pipe.StartResponse(id)
	defer sc.pipe.EndResponse(id)

	sc.mu.Lock()
	if sc.we != nil {
	defer sc.mu.Unlock()
	return sc.we
	}
	if sc.c == nil { // connection closed by user in the meantime
	defer sc.mu.Unlock()
	return ErrClosed
	}
	c := sc.c
	if sc.nread <= sc.nwritten {
	defer sc.mu.Unlock()
	return errors.New("persist server pipe count")
	}
	if resp.Close {
	// After signaling a keep-alive close, any pipelined unread
	// requests will be lost. It is up to the user to drain them
	// before signaling.
	sc.re = ErrPersistEOF
	}
	sc.mu.Unlock()

	err := resp.Write(c)
	sc.mu.Lock()
	defer sc.mu.Unlock()
	if err != nil {
	sc.we = err
	return err
	}
	sc.nwritten++

	return nil
	}

	// ClientConn is an artifact of Go's early HTTP implementation.
	// It is low-level, old, and unused by Go's current HTTP stack.
	// We should have deleted it before Go 1.
	//
	// Deprecated: Use Client or Transport in package net/http instead.
	type ClientConn struct {
	mu sync.Mutex // read-write protects the following fields
	c net.Conn
	r *bufio.Reader
	re, we error // read/write errors
	lastbody io.ReadCloser
	nread, nwritten int
	pipereq map[*http.Request]uint

	pipe textproto.Pipeline
	writeReq func(*http.Request, io.Writer) error
	}

	// NewClientConn is an artifact of Go's early HTTP implementation.
	// It is low-level, old, and unused by Go's current HTTP stack.
	// We should have deleted it before Go 1.
	//
	// Deprecated: Use the Client or Transport in package net/http instead.
	func NewClientConn(c net.Conn, r bufio.Reader) ClientConn {
	if r == nil {
	r = bufio.NewReader(c)
	}
	return &ClientConn{
	c: c,
	r: r,
	pipereq: make(map[*http.Request]uint),
	writeReq: (*http.Request).Write,
	}
	}

	// NewProxyClientConn is an artifact of Go's early HTTP implementation.
	// It is low-level, old, and unused by Go's current HTTP stack.
	// We should have deleted it before Go 1.
	//
	// Deprecated: Use the Client or Transport in package net/http instead.
	func NewProxyClientConn(c net.Conn, r bufio.Reader) ClientConn {
	cc := NewClientConn(c, r)
	cc.writeReq = (*http.Request).WriteProxy
	return cc
	}

	// Hijack detaches the ClientConn and returns the underlying connection as well
	// as the read-side bufio which may have some left over data. Hijack may be
	// called before the user or Read have signaled the end of the keep-alive
	// logic. The user should not call Hijack while Read or Write is in progress.
	func (cc ClientConn) Hijack() (c net.Conn, r bufio.Reader) {
	cc.mu.Lock()
	defer cc.mu.Unlock()
	c = cc.c
	r = cc.r
	cc.c = nil
	cc.r = nil
	return
	}

	// Close calls Hijack and then also closes the underlying connection.
	func (cc *ClientConn) Close() error {
	c, _ := cc.Hijack()
	if c != nil {
	return c.Close()
	}
	return nil
	}

	// Write writes a request. An ErrPersistEOF error is returned if the connection
	// has been closed in an HTTP keep-alive sense. If req.Close equals true, the
	// keep-alive connection is logically closed after this request and the opposing
	// server is informed. An ErrUnexpectedEOF indicates the remote closed the
	// underlying TCP connection, which is usually considered as graceful close.
	func (cc ClientConn) Write(req http.Request) error {
	var err error

	// Ensure ordered execution of Writes
	id := cc.pipe.Next()
	cc.pipe.StartRequest(id)
	defer func() {
	cc.pipe.EndRequest(id)
	if err != nil {
	cc.pipe.StartResponse(id)
	cc.pipe.EndResponse(id)
	} else {
	// Remember the pipeline id of this request
	cc.mu.Lock()
	cc.pipereq[req] = id
	cc.mu.Unlock()
	}
	}()

	cc.mu.Lock()
	if cc.re != nil { // no point sending if read-side closed or broken
	defer cc.mu.Unlock()
	return cc.re
	}
	if cc.we != nil {
	defer cc.mu.Unlock()
	return cc.we
	}
	if cc.c == nil { // connection closed by user in the meantime
	defer cc.mu.Unlock()
	return errClosed
	}
	c := cc.c
	if req.Close {
	// We write the EOF to the write-side error, because there
	// still might be some pipelined reads
	cc.we = ErrPersistEOF
	}
	cc.mu.Unlock()

	err = cc.writeReq(req, c)
	cc.mu.Lock()
	defer cc.mu.Unlock()
	if err != nil {
	cc.we = err
	return err
	}
	cc.nwritten++

	return nil
	}

	// Pending returns the number of unanswered requests
	// that have been sent on the connection.
	func (cc *ClientConn) Pending() int {
	cc.mu.Lock()
	defer cc.mu.Unlock()
	return cc.nwritten - cc.nread
	}

	// Read reads the next response from the wire. A valid response might be
	// returned together with an ErrPersistEOF, which means that the remote
	// requested that this be the last request serviced. Read can be called
	// concurrently with Write, but not with another Read.
	func (cc ClientConn) Read(req http.Request) (resp *http.Response, err error) {
	// Retrieve the pipeline ID of this request/response pair
	cc.mu.Lock()
	id, ok := cc.pipereq[req]
	delete(cc.pipereq, req)
	if !ok {
	cc.mu.Unlock()
	return nil, ErrPipeline
	}
	cc.mu.Unlock()

	// Ensure pipeline order
	cc.pipe.StartResponse(id)
	defer cc.pipe.EndResponse(id)

	cc.mu.Lock()
	if cc.re != nil {
	defer cc.mu.Unlock()
	return nil, cc.re
	}
	if cc.r == nil { // connection closed by user in the meantime
	defer cc.mu.Unlock()
	return nil, errClosed
	}
	r := cc.r
	lastbody := cc.lastbody
	cc.lastbody = nil
	cc.mu.Unlock()

	// Make sure body is fully consumed, even if user does not call body.Close
	if lastbody != nil {
	// body.Close is assumed to be idempotent and multiple calls to
	// it should return the error that its first invocation
	// returned.
	err = lastbody.Close()
	if err != nil {
	cc.mu.Lock()
	defer cc.mu.Unlock()
	cc.re = err
	return nil, err
	}
	}

	resp, err = http.ReadResponse(r, req)
	cc.mu.Lock()
	defer cc.mu.Unlock()
	if err != nil {
	cc.re = err
	return resp, err
	}
	cc.lastbody = resp.Body

	cc.nread++

	if resp.Close {
	cc.re = ErrPersistEOF // don't send any more requests
	return resp, cc.re
	}
	return resp, err
	}

	// Do is convenience method that writes a request and reads a response.
	func (cc ClientConn) Do(req http.Request) (*http.Response, error) {
	err := cc.Write(req)
	if err != nil {
	return nil, err
	}
	return cc.Read(req)
	}