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go-gemini/timeout.go

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package gemini
import (
"bytes"
"context"
"sync"
"time"
)
// TimeoutHandler returns a Handler that runs h with the given time limit.
//
// The new Handler calls h.ServeGemini to handle each request, but
// if a call runs for longer than its time limit, the handler responds with a
// 40 Temporary Failure error. After such a timeout, writes by h to its
// ResponseWriter will return ErrHandlerTimeout.
//
// TimeoutHandler does not support the Hijacker or Flusher interfaces.
func TimeoutHandler(h Handler, dt time.Duration) Handler {
return &timeoutHandler{
h: h,
dt: dt,
}
}
type timeoutHandler struct {
h Handler
dt time.Duration
}
func (t *timeoutHandler) ServeGemini(ctx context.Context, w ResponseWriter, r *Request) {
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ctx, cancel := context.WithTimeout(ctx, t.dt)
defer cancel()
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done := make(chan struct{})
tw := &timeoutWriter{}
panicChan := make(chan interface{}, 1)
go func() {
defer func() {
if p := recover(); p != nil {
panicChan <- p
}
}()
t.h.ServeGemini(ctx, tw, r)
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close(done)
}()
select {
case p := <-panicChan:
panic(p)
case <-done:
tw.mu.Lock()
defer tw.mu.Unlock()
if !tw.wroteHeader {
tw.status = StatusSuccess
}
w.WriteHeader(tw.status, tw.meta)
w.Write(tw.b.Bytes())
case <-ctx.Done():
tw.mu.Lock()
defer tw.mu.Unlock()
w.WriteHeader(StatusTemporaryFailure, "Timeout")
tw.timedOut = true
}
}
type timeoutWriter struct {
mu sync.Mutex
b bytes.Buffer
status Status
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meta string
mediatype string
wroteHeader bool
timedOut bool
}
func (w *timeoutWriter) MediaType(mediatype string) {
w.mu.Lock()
defer w.mu.Unlock()
w.mediatype = mediatype
}
func (w *timeoutWriter) Write(b []byte) (int, error) {
w.mu.Lock()
defer w.mu.Unlock()
if w.timedOut {
return 0, ErrHandlerTimeout
}
if !w.wroteHeader {
w.writeHeaderLocked(StatusSuccess, w.mediatype)
}
return w.b.Write(b)
}
func (w *timeoutWriter) WriteHeader(status Status, meta string) {
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w.mu.Lock()
defer w.mu.Unlock()
if w.timedOut {
return
}
w.writeHeaderLocked(status, meta)
}
func (w *timeoutWriter) writeHeaderLocked(status Status, meta string) {
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if w.wroteHeader {
return
}
w.status = status
w.meta = meta
w.wroteHeader = true
}