go-gemini/response.go
Adnan Maolood a65c3c3d4f Make ResponseWriter a struct
Make ResponseWriter a struct again so that it can be extended in a
backwards-compatible way.
2021-02-23 20:41:16 -05:00

247 lines
6.1 KiB
Go

package gemini
import (
"bufio"
"crypto/tls"
"io"
"net"
"strconv"
)
// The default media type for responses.
const defaultMediaType = "text/gemini; charset=utf-8"
// Response represents the response from a Gemini request.
//
// The Client returns Responses from servers once the response
// header has been received. The response body is streamed on demand
// as the response is read. If the network connection fails or the server
// terminates the response, Read calls return an error.
//
// It is the caller's responsibility to close the response.
type Response struct {
// Status contains the response status code.
Status Status
// Meta contains more information related to the response status.
// For successful responses, Meta should contain the media type of the response.
// For failure responses, Meta should contain a short description of the failure.
// Meta should not be longer than 1024 bytes.
Meta string
body io.ReadCloser
conn net.Conn
}
// ReadResponse reads a Gemini response from the provided io.ReadCloser.
func ReadResponse(rc io.ReadCloser) (*Response, error) {
resp := &Response{}
br := bufio.NewReader(rc)
// Read the status
statusB := make([]byte, 2)
if _, err := br.Read(statusB); err != nil {
return nil, err
}
status, err := strconv.Atoi(string(statusB))
if err != nil {
return nil, ErrInvalidResponse
}
resp.Status = Status(status)
// Read one space
if b, err := br.ReadByte(); err != nil {
return nil, err
} else if b != ' ' {
return nil, ErrInvalidResponse
}
// Read the meta
meta, err := br.ReadString('\r')
if err != nil {
return nil, err
}
// Trim carriage return
meta = meta[:len(meta)-1]
// Ensure meta is less than or equal to 1024 bytes
if len(meta) > 1024 {
return nil, ErrInvalidResponse
}
if resp.Status.Class() == StatusSuccess && meta == "" {
// Use default media type
meta = defaultMediaType
}
resp.Meta = meta
// Read terminating newline
if b, err := br.ReadByte(); err != nil {
return nil, err
} else if b != '\n' {
return nil, ErrInvalidResponse
}
if resp.Status.Class() == StatusSuccess {
resp.body = newReadCloserBody(br, rc)
} else {
resp.body = nopReadCloser{}
rc.Close()
}
return resp, nil
}
type nopReadCloser struct{}
func (nopReadCloser) Read(p []byte) (int, error) {
return 0, io.EOF
}
func (nopReadCloser) Close() error {
return nil
}
type readCloserBody struct {
br *bufio.Reader // used until empty
io.ReadCloser
}
func newReadCloserBody(br *bufio.Reader, rc io.ReadCloser) io.ReadCloser {
body := &readCloserBody{ReadCloser: rc}
if br.Buffered() != 0 {
body.br = br
}
return body
}
func (b *readCloserBody) Read(p []byte) (n int, err error) {
if b.br != nil {
if n := b.br.Buffered(); len(p) > n {
p = p[:n]
}
n, err = b.br.Read(p)
if b.br.Buffered() == 0 {
b.br = nil
}
return n, err
}
return b.ReadCloser.Read(p)
}
// Read reads data from the response body.
// The response body is streamed on demand as Read is called.
func (r *Response) Read(p []byte) (n int, err error) {
return r.body.Read(p)
}
// Close closes the response body.
func (r *Response) Close() error {
return r.body.Close()
}
// Conn returns the network connection on which the response was received.
func (r *Response) Conn() net.Conn {
return r.conn
}
// TLS returns information about the TLS connection on which the
// response was received.
func (r *Response) TLS() *tls.ConnectionState {
if tlsConn, ok := r.conn.(*tls.Conn); ok {
state := tlsConn.ConnectionState()
return &state
}
return nil
}
// A ResponseWriter interface is used by a Gemini handler to construct
// a Gemini response.
//
// A ResponseWriter may not be used after the Handler.ServeGemini method
// has returned.
type ResponseWriter struct {
b *bufio.Writer
closer io.Closer
mediatype string
wroteHeader bool
bodyAllowed bool
}
// NewResponseWriter returns a ResponseWriter that uses the provided io.WriteCloser.
func NewResponseWriter(wc io.WriteCloser) *ResponseWriter {
return &ResponseWriter{
b: bufio.NewWriter(wc),
closer: wc,
}
}
// SetMediaType sets the media type that will be sent by Write for a
// successful response. If no media type is set, a default of
// "text/gemini; charset=utf-8" will be used.
//
// Setting the media type after a call to Write or WriteHeader has
// no effect.
func (w *ResponseWriter) SetMediaType(mediatype string) {
w.mediatype = mediatype
}
// Write writes the data to the connection as part of a Gemini response.
//
// If WriteHeader has not yet been called, Write calls WriteHeader with
// StatusSuccess and the media type set in SetMediaType before writing the data.
// If no media type was set, Write uses a default media type of
// "text/gemini; charset=utf-8".
func (w *ResponseWriter) Write(b []byte) (int, error) {
if !w.wroteHeader {
meta := w.mediatype
if meta == "" {
// Use default media type
meta = defaultMediaType
}
w.WriteHeader(StatusSuccess, meta)
}
if !w.bodyAllowed {
return 0, ErrBodyNotAllowed
}
return w.b.Write(b)
}
// WriteHeader sends a Gemini response header with the provided
// status code and meta.
//
// If WriteHeader is not called explicitly, the first call to Write
// will trigger an implicit call to WriteHeader with a successful
// status code and the media type set in SetMediaType.
//
// The provided code must be a valid Gemini status code.
// The provided meta must not be longer than 1024 bytes.
// Only one header may be written.
func (w *ResponseWriter) WriteHeader(status Status, meta string) {
if w.wroteHeader {
return
}
if status.Class() == StatusSuccess {
w.bodyAllowed = true
}
w.b.WriteString(strconv.Itoa(int(status)))
w.b.WriteByte(' ')
w.b.WriteString(meta)
w.b.Write(crlf)
w.wroteHeader = true
}
// Flush sends any buffered data to the client.
func (w *ResponseWriter) Flush() error {
if !w.wroteHeader {
w.WriteHeader(StatusTemporaryFailure, "Temporary failure")
}
// Write errors from WriteHeader will be returned here.
return w.b.Flush()
}
// Close closes the connection.
// Any blocked Write operations will be unblocked and return errors.
func (w *ResponseWriter) Close() error {
return w.closer.Close()
}