Golang context.Context類代碼示例

func transaction(ctx context.Context) []byte {
	v := ctx.Value(ContextKey("transaction"))
	if v == nil {
		return nil
	} else {
		return v.([]byte)
	}
}

// baseUrl gets the base url active for the datastore service
// defaults to "https://www.googleapis.com/datastore/v1beta2/datasets/" if none was specified
func baseUrl(ctx context.Context) string {
	v := ctx.Value(ContextKey("base_url"))
	if v == nil {
		return "https://www.googleapis.com/datastore/v1beta2/datasets/"
	} else {
		return v.(string)
	}
}

func contextClient(ctx context.Context) (*http.Client, error) {
	for _, fn := range contextClientFuncs {
		c, err := fn(ctx)
		if err != nil {
			return nil, err
		}
		if c != nil {
			return c, nil
		}
	}
	if hc, ok := ctx.Value(HTTPClient).(*http.Client); ok {
		return hc, nil
	}
	return http.DefaultClient, nil
}

// Upload starts the process of a resumable upload with a cancellable context.
// It retries indefinitely (with a pause of uploadPause between attempts) until cancelled.
// It is called from the auto-generated API code and is not visible to the user.
// rx is private to the auto-generated API code.
func (rx *ResumableUpload) Upload(ctx context.Context) (*http.Response, error) {
	var res *http.Response
	var err error
	for {
		res, err = rx.transferChunks(ctx)
		if err != nil || res.StatusCode == http.StatusCreated || res.StatusCode == http.StatusOK {
			return res, err
		}
		select { // Check for cancellation
		case <-ctx.Done():
			res.StatusCode = http.StatusRequestTimeout
			return res, ctx.Err()
		default:
		}
		sleep(uploadPause)
	}
	return res, err
}

func (rx *ResumableUpload) transferChunks(ctx context.Context) (*http.Response, error) {
	start, res, err := rx.transferStatus()
	if err != nil || res.StatusCode != statusResumeIncomplete {
		return res, err
	}

	for {
		select { // Check for cancellation
		case <-ctx.Done():
			res.StatusCode = http.StatusRequestTimeout
			return res, ctx.Err()
		default:
		}
		reqSize := rx.ContentLength - start
		if reqSize > chunkSize {
			reqSize = chunkSize
		}
		r := io.NewSectionReader(rx.Media, start, reqSize)
		req, _ := http.NewRequest("POST", rx.URI, r)
		req.ContentLength = reqSize
		req.Header.Set("Content-Range", fmt.Sprintf("bytes %v-%v/%v", start, start+reqSize-1, rx.ContentLength))
		req.Header.Set("Content-Type", rx.MediaType)
		req.Header.Set("User-Agent", rx.UserAgent)
		res, err = rx.Client.Do(req)
		start += reqSize
		if err == nil && (res.StatusCode == statusResumeIncomplete || res.StatusCode == http.StatusOK) {
			rx.mu.Lock()
			rx.progress = start // keep track of number of bytes sent so far
			rx.mu.Unlock()
			if rx.Callback != nil {
				rx.Callback(start, rx.ContentLength)
			}
		}
		if err != nil || res.StatusCode != statusResumeIncomplete {
			break
		}
	}
	return res, err
}

// ctxNamespace returns the active namespace for a context.
// It defaults to "" if no namespace was specified.
func ctxNamespace(ctx context.Context) string {
	v, _ := ctx.Value(nsKey{}).(string)
	return v
}

// cc returns the internal *cloudContext (cc) state for a context.Context.
// It panics if the user did it wrong.
func cc(ctx context.Context) *cloudContext {
	if c, ok := ctx.Value(contextKey{}).(*cloudContext); ok {
		return c
	}
	panic("invalid context.Context type; it should be created with cloud.NewContext")
}