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// Copyright 2022 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"
"fmt"
"net"
"time"
)
// A ResponseController is used by an HTTP handler to control the response.
//
// A ResponseController may not be used after the [Handler.ServeHTTP] method has returned.
type ResponseController struct {
rw ResponseWriter
}
// NewResponseController creates a [ResponseController] for a request.
//
// The ResponseWriter should be the original value passed to the [Handler.ServeHTTP] method,
// or have an Unwrap method returning the original ResponseWriter.
//
// If the ResponseWriter implements any of the following methods, the ResponseController
// will call them as appropriate:
//
// Flush()
// FlushError() error // alternative Flush returning an error
// Hijack() (net.Conn, *bufio.ReadWriter, error)
// SetReadDeadline(deadline time.Time) error
// SetWriteDeadline(deadline time.Time) error
// EnableFullDuplex() error
//
// If the ResponseWriter does not support a method, ResponseController returns
// an error matching [ErrNotSupported].
func NewResponseController(rw ResponseWriter) *ResponseController {
return &ResponseController{rw}
}
type rwUnwrapper interface {
Unwrap() ResponseWriter
}
// Flush flushes buffered data to the client.
func (c *ResponseController) Flush() error {
rw := c.rw
for {
switch t := rw.(type) {
case interface{ FlushError() error }:
return t.FlushError()
case Flusher:
t.Flush()
return nil
case rwUnwrapper:
rw = t.Unwrap()
default:
return errNotSupported()
}
}
}
// Hijack lets the caller take over the connection.
// See the Hijacker interface for details.
func (c *ResponseController) Hijack() (net.Conn, *bufio.ReadWriter, error) {
rw := c.rw
for {
switch t := rw.(type) {
case Hijacker:
return t.Hijack()
case rwUnwrapper:
rw = t.Unwrap()
default:
return nil, nil, errNotSupported()
}
}
}
// SetReadDeadline sets the deadline for reading the entire request, including the body.
// Reads from the request body after the deadline has been exceeded will return an error.
// A zero value means no deadline.
//
// Setting the read deadline after it has been exceeded will not extend it.
func (c *ResponseController) SetReadDeadline(deadline time.Time) error {
rw := c.rw
for {
switch t := rw.(type) {
case interface{ SetReadDeadline(time.Time) error }:
return t.SetReadDeadline(deadline)
case rwUnwrapper:
rw = t.Unwrap()
default:
return errNotSupported()
}
}
}
// SetWriteDeadline sets the deadline for writing the response.
// Writes to the response body after the deadline has been exceeded will not block,
// but may succeed if the data has been buffered.
// A zero value means no deadline.
//
// Setting the write deadline after it has been exceeded will not extend it.
func (c *ResponseController) SetWriteDeadline(deadline time.Time) error {
rw := c.rw
for {
switch t := rw.(type) {
case interface{ SetWriteDeadline(time.Time) error }:
return t.SetWriteDeadline(deadline)
case rwUnwrapper:
rw = t.Unwrap()
default:
return errNotSupported()
}
}
}
// EnableFullDuplex indicates that the request handler will interleave reads from [Request.Body]
// with writes to the [ResponseWriter].
//
// For HTTP/1 requests, the Go HTTP server by default consumes any unread portion of
// the request body before beginning to write the response, preventing handlers from
// concurrently reading from the request and writing the response.
// Calling EnableFullDuplex disables this behavior and permits handlers to continue to read
// from the request while concurrently writing the response.
//
// For HTTP/2 requests, the Go HTTP server always permits concurrent reads and responses.
func (c *ResponseController) EnableFullDuplex() error {
rw := c.rw
for {
switch t := rw.(type) {
case interface{ EnableFullDuplex() error }:
return t.EnableFullDuplex()
case rwUnwrapper:
rw = t.Unwrap()
default:
return errNotSupported()
}
}
}
// errNotSupported returns an error that Is ErrNotSupported,
// but is not == to it.
func errNotSupported() error {
return fmt.Errorf("%w", ErrNotSupported)
}
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