1/*
 2 *
 3 * Copyright 2020 gRPC authors.
 4 *
 5 * Licensed under the Apache License, Version 2.0 (the "License");
 6 * you may not use this file except in compliance with the License.
 7 * You may obtain a copy of the License at
 8 *
 9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19package grpcutil
20
21import (
22	"strconv"
23	"time"
24)
25
26const maxTimeoutValue int64 = 100000000 - 1
27
28// div does integer division and round-up the result. Note that this is
29// equivalent to (d+r-1)/r but has less chance to overflow.
30func div(d, r time.Duration) int64 {
31	if d%r > 0 {
32		return int64(d/r + 1)
33	}
34	return int64(d / r)
35}
36
37// EncodeDuration encodes the duration to the format grpc-timeout header
38// accepts.
39//
40// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests
41func EncodeDuration(t time.Duration) string {
42	// TODO: This is simplistic and not bandwidth efficient. Improve it.
43	if t <= 0 {
44		return "0n"
45	}
46	if d := div(t, time.Nanosecond); d <= maxTimeoutValue {
47		return strconv.FormatInt(d, 10) + "n"
48	}
49	if d := div(t, time.Microsecond); d <= maxTimeoutValue {
50		return strconv.FormatInt(d, 10) + "u"
51	}
52	if d := div(t, time.Millisecond); d <= maxTimeoutValue {
53		return strconv.FormatInt(d, 10) + "m"
54	}
55	if d := div(t, time.Second); d <= maxTimeoutValue {
56		return strconv.FormatInt(d, 10) + "S"
57	}
58	if d := div(t, time.Minute); d <= maxTimeoutValue {
59		return strconv.FormatInt(d, 10) + "M"
60	}
61	// Note that maxTimeoutValue * time.Hour > MaxInt64.
62	return strconv.FormatInt(div(t, time.Hour), 10) + "H"
63}