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package cancel
import (
"context"
"fmt"
"net/http"
"sync"
)
// HTTPRequestCanceller tracks a cancelable operation.
type HTTPRequestCanceller struct {
reqCancel map[*http.Request]context.CancelFunc
lock sync.Mutex
}
// NewHTTPRequestCanceller returns a new HTTPRequestCanceller struct.
func NewHTTPRequestCanceller() *HTTPRequestCanceller {
c := HTTPRequestCanceller{}
c.lock.Lock()
c.reqCancel = make(map[*http.Request]context.CancelFunc)
c.lock.Unlock()
return &c
}
// Cancelable indicates whether there are operations that support cancellation.
func (c *HTTPRequestCanceller) Cancelable() bool {
c.lock.Lock()
length := len(c.reqCancel)
c.lock.Unlock()
return length > 0
}
// Cancel will attempt to cancel all ongoing operations.
func (c *HTTPRequestCanceller) Cancel() error {
if !c.Cancelable() {
return fmt.Errorf("This operation can't be canceled at this time")
}
c.lock.Lock()
for req, cancel := range c.reqCancel {
cancel()
delete(c.reqCancel, req)
}
c.lock.Unlock()
return nil
}
// CancelableDownload performs an http request and allows for it to be canceled at any time.
func CancelableDownload(c *HTTPRequestCanceller, do func(req *http.Request) (*http.Response, error), req *http.Request) (*http.Response, chan bool, error) {
chDone := make(chan bool)
ctx, cancel := context.WithCancel(req.Context())
req = req.WithContext(ctx)
if c != nil {
c.lock.Lock()
c.reqCancel[req] = cancel
c.lock.Unlock()
}
go func() {
<-chDone
if c != nil {
c.lock.Lock()
cancel()
delete(c.reqCancel, req)
c.lock.Unlock()
}
}()
resp, err := do(req)
if err != nil {
close(chDone)
return nil, nil, err
}
return resp, chDone, nil
}
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