return cipher.NewCBCDecrypter(block, iv)
	}
	return cipher.NewCBCEncrypter(block, iv)
}

// macSHA1 returns a SHA-1 based constant time MAC.
func macSHA1(key []byte) hash.Hash {
	h := sha1.New
	// The BoringCrypto SHA1 does not have a constant-time
	// checksum function, so don't try to use it.
	if !boring.Enabled {
		h = newConstantTimeHash(h)
	}
	return hmac.New(h, key)
}

		for {
			<-uniqueMapCleanup
			cleanup()
		}
	}(f)
}

func clearpools() {
	// clear sync.Pools
	if poolcleanup != nil {
		poolcleanup()
	}

	// clear boringcrypto caches
	for _, p := range boringCaches {
		atomicstorep(p, nil)
	}

	// clear unique maps
	if uniqueMapCleanup != nil {
		select {
		case uniqueMapCleanup <- struct{}{}:
		default: