Method cacheFile

internal/backend/cache/backend.go:95–136

(ctx context.Context, h backend.Handle)

}

func (b *Backend) cacheFile(ctx context.Context, h backend.Handle) error {
	finish := make(chan struct{})

	b.inProgressMutex.Lock()
	other, alreadyDownloading := b.inProgress[h]
	if !alreadyDownloading {
		b.inProgress[h] = finish
	}
	b.inProgressMutex.Unlock()

	if alreadyDownloading {
		debug.Log("readahead %v is already performed by somebody else, delegating...", h)
		<-other
		debug.Log("download %v finished", h)
		return nil
	}

	defer func() {
		// signal other waiting goroutines that the file may now be cached
		close(finish)

		// remove the finish channel from the map
		b.inProgressMutex.Lock()
		delete(b.inProgress, h)
		b.inProgressMutex.Unlock()
	}()

	// test again, maybe the file was cached in the meantime
	if !b.Cache.Has(h) {
		// nope, it's still not in the cache, pull it from the repo and save it
		err := b.Backend.Load(ctx, h, 0, 0, func(rd io.Reader) error {
			return b.Cache.save(h, rd)
		})
		if err != nil {
			// try to remove from the cache, ignore errors
			_, _ = b.Cache.remove(h)
		}
		return err
	}

	return nil
}

// loadFromCache will try to load the file from the cache.
func (b *Backend) loadFromCache(h backend.Handle, length int, offset int64, consumer func(rd io.Reader) error) (bool, error) {