http: persistent connection objects
R=rsc
CC=golang-dev
https://golang.org/cl/203051
diff --git a/src/pkg/http/persist.go b/src/pkg/http/persist.go
new file mode 100644
index 0000000..a4da3da
--- /dev/null
+++ b/src/pkg/http/persist.go
@@ -0,0 +1,285 @@
+// 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 http
+
+import (
+ "bufio"
+ "container/list"
+ "io"
+ "net"
+ "os"
+ "sync"
+)
+
+var ErrPersistEOF = &ProtocolError{"persistent connection closed"}
+
+// A ServerConn reads requests and sends responses over an underlying
+// connection, until the HTTP keepalive logic commands an end. ServerConn
+// does not close the underlying connection. Instead, the user calls Close
+// and regains control over the connection. ServerConn supports pipe-lining,
+// i.e. requests can be read out of sync (but in the same order) while the
+// respective responses are sent.
+type ServerConn struct {
+ c net.Conn
+ r *bufio.Reader
+ clsd bool // indicates a graceful close
+ re, we os.Error // read/write errors
+ lastBody io.ReadCloser
+ nread, nwritten int
+ lk sync.Mutex // protected read/write to re,we
+}
+
+// NewServerConn returns a new ServerConn reading and writing c. If r is not
+// nil, it is the buffer to use when reading c.
+func NewServerConn(c net.Conn, r *bufio.Reader) *ServerConn {
+ if r == nil {
+ r = bufio.NewReader(c)
+ }
+ return &ServerConn{c: c, r: r}
+}
+
+// Close detaches the ServerConn and returns the underlying connection as well
+// as the read-side bufio which may have some left over data. Close may be
+// called before Read has signaled the end of the keep-alive logic. The user
+// should not call Close while Read or Write is in progress.
+func (sc *ServerConn) Close() (c net.Conn, r *bufio.Reader) {
+ c = sc.c
+ r = sc.r
+ sc.c = nil
+ sc.r = nil
+ return
+}
+
+// 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). Read can be called concurrently with Write, but not
+// with another Read.
+func (sc *ServerConn) Read() (req *Request, err os.Error) {
+
+ sc.lk.Lock()
+ if sc.we != nil { // no point receiving if write-side broken or closed
+ defer sc.lk.Unlock()
+ return nil, sc.we
+ }
+ if sc.re != nil {
+ defer sc.lk.Unlock()
+ return nil, sc.re
+ }
+ sc.lk.Unlock()
+
+ // Make sure body is fully consumed, even if user does not call body.Close
+ if sc.lastBody != nil {
+ // body.Close is assumed to be idempotent and multiple calls to
+ // it should return the error that its first invokation
+ // returned.
+ err = sc.lastBody.Close()
+ sc.lastBody = nil
+ if err != nil {
+ sc.lk.Lock()
+ defer sc.lk.Unlock()
+ sc.re = err
+ return nil, err
+ }
+ }
+
+ req, err = ReadRequest(sc.r)
+ if err != nil {
+ sc.lk.Lock()
+ defer sc.lk.Unlock()
+ 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
+ }
+ }
+ sc.lastBody = req.Body
+ sc.nread++
+ if req.Close {
+ sc.lk.Lock()
+ defer sc.lk.Unlock()
+ sc.re = ErrPersistEOF
+ return req, sc.re
+ }
+ return
+}
+
+// Write writes a repsonse. 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.
+// Write can be called concurrently with Read, but not with another Write.
+func (sc *ServerConn) Write(resp *Response) os.Error {
+
+ sc.lk.Lock()
+ if sc.we != nil {
+ defer sc.lk.Unlock()
+ return sc.we
+ }
+ sc.lk.Unlock()
+ if sc.nread <= sc.nwritten {
+ return os.NewError("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.lk.Lock()
+ sc.re = ErrPersistEOF
+ sc.lk.Unlock()
+ }
+
+ err := resp.Write(sc.c)
+ if err != nil {
+ sc.lk.Lock()
+ defer sc.lk.Unlock()
+ sc.we = err
+ return err
+ }
+ sc.nwritten++
+
+ return nil
+}
+
+// A ClientConn sends request and receives headers over an underlying
+// connection, while respecting the HTTP keepalive logic. ClientConn is not
+// responsible for closing the underlying connection. One must call Close to
+// regain control of that connection and deal with it as desired.
+type ClientConn struct {
+ c net.Conn
+ r *bufio.Reader
+ re, we os.Error // read/write errors
+ lastBody io.ReadCloser
+ nread, nwritten int
+ reqm list.List // request methods in order of execution
+ lk sync.Mutex // protects read/write to reqm,re,we
+}
+
+// NewClientConn returns a new ClientConn reading and writing c. If r is not
+// nil, it is the buffer to use when reading c.
+func NewClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
+ if r == nil {
+ r = bufio.NewReader(c)
+ }
+ return &ClientConn{c: c, r: r}
+}
+
+// Close detaches the ClientConn and returns the underlying connection as well
+// as the read-side bufio which may have some left over data. Close may be
+// called before the user or Read have signaled the end of the keep-alive
+// logic. The user should not call Close while Read or Write is in progress.
+func (cc *ClientConn) Close() (c net.Conn, r *bufio.Reader) {
+ c = cc.c
+ r = cc.r
+ cc.c = nil
+ cc.r = nil
+ cc.lk.Lock()
+ cc.reqm.Init()
+ cc.lk.Unlock()
+ return
+}
+
+// Write writes a request. An ErrPersistEOF error is returned if the connection
+// has been closed in an HTTP keepalive sense. If req.Close equals true, the
+// keepalive 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.
+// Write can be called concurrently with Read, but not with another Write.
+func (cc *ClientConn) Write(req *Request) os.Error {
+
+ cc.lk.Lock()
+ if cc.re != nil { // no point sending if read-side closed or broken
+ defer cc.lk.Unlock()
+ return cc.re
+ }
+ if cc.we != nil {
+ defer cc.lk.Unlock()
+ return cc.we
+ }
+ cc.lk.Unlock()
+
+ if req.Close {
+ // We write the EOF to the write-side error, because there
+ // still might be some pipelined reads
+ cc.lk.Lock()
+ cc.we = ErrPersistEOF
+ cc.lk.Unlock()
+ }
+
+ err := req.Write(cc.c)
+ if err != nil {
+ cc.lk.Lock()
+ defer cc.lk.Unlock()
+ cc.we = err
+ return err
+ }
+ cc.nwritten++
+ cc.lk.Lock()
+ cc.reqm.PushBack(req.Method)
+ cc.lk.Unlock()
+
+ return nil
+}
+
+// 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() (resp *Response, err os.Error) {
+
+ cc.lk.Lock()
+ if cc.re != nil {
+ defer cc.lk.Unlock()
+ return nil, cc.re
+ }
+ cc.lk.Unlock()
+
+ if cc.nread >= cc.nwritten {
+ return nil, os.NewError("persist client pipe count")
+ }
+
+ // Make sure body is fully consumed, even if user does not call body.Close
+ if cc.lastBody != nil {
+ // body.Close is assumed to be idempotent and multiple calls to
+ // it should return the error that its first invokation
+ // returned.
+ err = cc.lastBody.Close()
+ cc.lastBody = nil
+ if err != nil {
+ cc.lk.Lock()
+ defer cc.lk.Unlock()
+ cc.re = err
+ return nil, err
+ }
+ }
+
+ cc.lk.Lock()
+ m := cc.reqm.Front()
+ cc.reqm.Remove(m)
+ cc.lk.Unlock()
+ resp, err = ReadResponse(cc.r, m.Value.(string))
+ if err != nil {
+ cc.lk.Lock()
+ defer cc.lk.Unlock()
+ cc.re = err
+ return
+ }
+ cc.lastBody = resp.Body
+
+ cc.nread++
+
+ if resp.Close {
+ cc.lk.Lock()
+ defer cc.lk.Unlock()
+ cc.re = ErrPersistEOF // don't send any more requests
+ return resp, cc.re
+ }
+ return
+}
