duration.go

Documentation: google.golang.org/grpc/internal/serviceconfig

     1  /*
     2   *
     3   * Copyright 2023 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  
    19  package serviceconfig
    20  
    21  import (
    22  	"encoding/json"
    23  	"fmt"
    24  	"math"
    25  	"strconv"
    26  	"strings"
    27  	"time"
    28  )
    29  
    30  // Duration defines JSON marshal and unmarshal methods to conform to the
    31  // protobuf JSON spec defined [here].
    32  //
    33  // [here]: https://protobuf.dev/reference/protobuf/google.protobuf/#duration
    34  type Duration time.Duration
    35  
    36  func (d Duration) String() string {
    37  	return fmt.Sprint(time.Duration(d))
    38  }
    39  
    40  // MarshalJSON converts from d to a JSON string output.
    41  func (d Duration) MarshalJSON() ([]byte, error) {
    42  	ns := time.Duration(d).Nanoseconds()
    43  	sec := ns / int64(time.Second)
    44  	ns = ns % int64(time.Second)
    45  
    46  	var sign string
    47  	if sec < 0 || ns < 0 {
    48  		sign, sec, ns = "-", -1*sec, -1*ns
    49  	}
    50  
    51  	// Generated output always contains 0, 3, 6, or 9 fractional digits,
    52  	// depending on required precision.
    53  	str := fmt.Sprintf("%s%d.%09d", sign, sec, ns)
    54  	str = strings.TrimSuffix(str, "000")
    55  	str = strings.TrimSuffix(str, "000")
    56  	str = strings.TrimSuffix(str, ".000")
    57  	return []byte(fmt.Sprintf("\"%ss\"", str)), nil
    58  }
    59  
    60  // UnmarshalJSON unmarshals b as a duration JSON string into d.
    61  func (d *Duration) UnmarshalJSON(b []byte) error {
    62  	var s string
    63  	if err := json.Unmarshal(b, &s); err != nil {
    64  		return err
    65  	}
    66  	if !strings.HasSuffix(s, "s") {
    67  		return fmt.Errorf("malformed duration %q: missing seconds unit", s)
    68  	}
    69  	neg := false
    70  	if s[0] == '-' {
    71  		neg = true
    72  		s = s[1:]
    73  	}
    74  	ss := strings.SplitN(s[:len(s)-1], ".", 3)
    75  	if len(ss) > 2 {
    76  		return fmt.Errorf("malformed duration %q: too many decimals", s)
    77  	}
    78  	// hasDigits is set if either the whole or fractional part of the number is
    79  	// present, since both are optional but one is required.
    80  	hasDigits := false
    81  	var sec, ns int64
    82  	if len(ss[0]) > 0 {
    83  		var err error
    84  		if sec, err = strconv.ParseInt(ss[0], 10, 64); err != nil {
    85  			return fmt.Errorf("malformed duration %q: %v", s, err)
    86  		}
    87  		// Maximum seconds value per the durationpb spec.
    88  		const maxProtoSeconds = 315_576_000_000
    89  		if sec > maxProtoSeconds {
    90  			return fmt.Errorf("out of range: %q", s)
    91  		}
    92  		hasDigits = true
    93  	}
    94  	if len(ss) == 2 && len(ss[1]) > 0 {
    95  		if len(ss[1]) > 9 {
    96  			return fmt.Errorf("malformed duration %q: too many digits after decimal", s)
    97  		}
    98  		var err error
    99  		if ns, err = strconv.ParseInt(ss[1], 10, 64); err != nil {
   100  			return fmt.Errorf("malformed duration %q: %v", s, err)
   101  		}
   102  		for i := 9; i > len(ss[1]); i-- {
   103  			ns *= 10
   104  		}
   105  		hasDigits = true
   106  	}
   107  	if !hasDigits {
   108  		return fmt.Errorf("malformed duration %q: contains no numbers", s)
   109  	}
   110  
   111  	if neg {
   112  		sec *= -1
   113  		ns *= -1
   114  	}
   115  
   116  	// Maximum/minimum seconds/nanoseconds representable by Go's time.Duration.
   117  	const maxSeconds = math.MaxInt64 / int64(time.Second)
   118  	const maxNanosAtMaxSeconds = math.MaxInt64 % int64(time.Second)
   119  	const minSeconds = math.MinInt64 / int64(time.Second)
   120  	const minNanosAtMinSeconds = math.MinInt64 % int64(time.Second)
   121  
   122  	if sec > maxSeconds || (sec == maxSeconds && ns >= maxNanosAtMaxSeconds) {
   123  		*d = Duration(math.MaxInt64)
   124  	} else if sec < minSeconds || (sec == minSeconds && ns <= minNanosAtMinSeconds) {
   125  		*d = Duration(math.MinInt64)
   126  	} else {
   127  		*d = Duration(sec*int64(time.Second) + ns)
   128  	}
   129  	return nil
   130  }
   131
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