2020-10-24 19:15:32 +00:00
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package gemini
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2020-10-21 21:07:28 +00:00
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import (
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"bufio"
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"crypto/tls"
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2020-10-27 23:16:55 +00:00
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"io"
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2020-10-21 21:07:28 +00:00
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"strconv"
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)
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2021-02-17 18:36:16 +00:00
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// The default media type for responses.
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const defaultMediaType = "text/gemini; charset=utf-8"
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2021-02-14 21:23:38 +00:00
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// Response represents the response from a Gemini request.
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//
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// The Client returns Responses from servers once the response
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// header has been received. The response body is streamed on demand
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// as the Body field is read.
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type Response struct {
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// Status contains the response status code.
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Status int
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// Meta contains more information related to the response status.
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// For successful responses, Meta should contain the media type of the response.
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// For failure responses, Meta should contain a short description of the failure.
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// Meta should not be longer than 1024 bytes.
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Meta string
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// Body represents the response body.
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//
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// The response body is streamed on demand as the Body field
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// is read. If the network connection fails or the server
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// terminates the response, Body.Read calls return an error.
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//
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// The Gemini client guarantees that Body is always
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// non-nil, even on responses without a body or responses with
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// a zero-length body. It is the caller's responsibility to
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// close Body.
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Body io.ReadCloser
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// TLS contains information about the TLS connection on which the
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// response was received. It is nil for unencrypted responses.
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TLS *tls.ConnectionState
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}
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2020-12-18 06:41:14 +00:00
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// ReadResponse reads a Gemini response from the provided io.ReadCloser.
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func ReadResponse(rc io.ReadCloser) (*Response, error) {
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resp := &Response{}
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br := bufio.NewReader(rc)
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// Read the status
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statusB := make([]byte, 2)
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if _, err := br.Read(statusB); err != nil {
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return nil, err
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}
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status, err := strconv.Atoi(string(statusB))
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if err != nil {
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return nil, ErrInvalidResponse
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}
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resp.Status = status
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// Read one space
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if b, err := br.ReadByte(); err != nil {
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return nil, err
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} else if b != ' ' {
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return nil, ErrInvalidResponse
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}
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// Read the meta
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meta, err := br.ReadString('\r')
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if err != nil {
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return nil, err
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}
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// Trim carriage return
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meta = meta[:len(meta)-1]
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// Ensure meta is less than or equal to 1024 bytes
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if len(meta) > 1024 {
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return nil, ErrInvalidResponse
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}
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if StatusClass(status) == StatusSuccess && meta == "" {
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// Use default media type
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meta = defaultMediaType
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}
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resp.Meta = meta
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// Read terminating newline
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if b, err := br.ReadByte(); err != nil {
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return nil, err
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} else if b != '\n' {
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return nil, ErrInvalidResponse
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}
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if StatusClass(status) == StatusSuccess {
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resp.Body = newReadCloserBody(br, rc)
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} else {
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resp.Body = nopReadCloser{}
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rc.Close()
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}
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return resp, nil
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}
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type nopReadCloser struct{}
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func (nopReadCloser) Read(p []byte) (int, error) {
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return 0, io.EOF
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}
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func (nopReadCloser) Close() error {
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return nil
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}
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type readCloserBody struct {
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br *bufio.Reader // used until empty
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io.ReadCloser
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}
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func newReadCloserBody(br *bufio.Reader, rc io.ReadCloser) io.ReadCloser {
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body := &readCloserBody{ReadCloser: rc}
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if br.Buffered() != 0 {
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body.br = br
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}
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return body
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}
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func (b *readCloserBody) Read(p []byte) (n int, err error) {
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if b.br != nil {
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if n := b.br.Buffered(); len(p) > n {
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p = p[:n]
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}
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n, err = b.br.Read(p)
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if b.br.Buffered() == 0 {
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b.br = nil
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}
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return n, err
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}
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return b.ReadCloser.Read(p)
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}
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2021-02-17 18:36:16 +00:00
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// A ResponseWriter interface is used by a Gemini handler to construct
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// a Gemini response.
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//
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// A ResponseWriter may not be used after the Handler.ServeGemini method
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// has returned.
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type ResponseWriter interface {
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// MediaType sets the media type that will be sent by Write for a
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// successful response. If no media type is set, a default of
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// "text/gemini; charset=utf-8" will be used.
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//
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// Setting the media type after a call to Write or WriteHeader has
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// no effect.
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MediaType(string)
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// Write writes the data to the connection as part of a Gemini response.
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//
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// If WriteHeader has not yet been called, Write calls WriteHeader with
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// StatusSuccess and the media type set in MediaType before writing the data.
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// If no media type was set, Write uses a default media type of
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// "text/gemini; charset=utf-8".
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Write([]byte) (int, error)
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// WriteHeader sends a Gemini response header with the provided
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// status code and meta.
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//
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// If WriteHeader is not called explicitly, the first call to Write
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// will trigger an implicit call to WriteHeader with a successful
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// status code and the media type set in MediaType.
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//
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// The provided code must be a valid Gemini status code.
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// The provided meta must not be longer than 1024 bytes.
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// Only one header may be written.
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WriteHeader(statusCode int, meta string)
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}
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// The Flusher interface is implemented by ResponseWriters that allow a
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// Gemini handler to flush buffered data to the client.
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//
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// The default Gemini ResponseWriter implementation supports Flusher,
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// but ResponseWriter wrappers may not. Handlers should always test
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// for this ability at runtime.
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type Flusher interface {
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// Flush sends any buffered data to the client.
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Flush() error
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}
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type responseWriter struct {
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b *bufio.Writer
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mediatype string
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wroteHeader bool
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bodyAllowed bool
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}
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// NewResponseWriter returns a ResponseWriter that uses the provided io.Writer.
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func NewResponseWriter(w io.Writer) ResponseWriter {
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return newResponseWriter(w)
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}
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func newResponseWriter(w io.Writer) *responseWriter {
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return &responseWriter{
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b: bufio.NewWriter(w),
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}
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}
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func (w *responseWriter) MediaType(mediatype string) {
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w.mediatype = mediatype
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}
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func (w *responseWriter) Write(b []byte) (int, error) {
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if !w.wroteHeader {
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meta := w.mediatype
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if meta == "" {
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// Use default media type
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meta = defaultMediaType
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}
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w.WriteHeader(StatusSuccess, meta)
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}
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if !w.bodyAllowed {
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return 0, ErrBodyNotAllowed
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}
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return w.b.Write(b)
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}
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func (w *responseWriter) WriteHeader(statusCode int, meta string) {
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if w.wroteHeader {
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return
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}
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if StatusClass(statusCode) == StatusSuccess {
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w.bodyAllowed = true
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}
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w.b.WriteString(strconv.Itoa(statusCode))
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w.b.WriteByte(' ')
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w.b.WriteString(meta)
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w.b.Write(crlf)
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w.wroteHeader = true
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}
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func (w *responseWriter) Flush() error {
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if !w.wroteHeader {
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w.WriteHeader(StatusTemporaryFailure, "Temporary failure")
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}
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// Write errors from writeHeader will be returned here.
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return w.b.Flush()
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}
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