common/data/text/units/units.go

// Copyright 2015 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package units

import (
	"flag"
	"fmt"
	"strconv"
)

var units = []string{"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"}

// Size represents a size in bytes that knows how to print itself.
//
// Size implements flag.Value interface.
type Size int64

var _ flag.Value = (*Size)(nil)

// String returns pretty printed file size.
func (s Size) String() string {
	return SizeToString(int64(s))
}

// Set sets Size from a given flag args.
func (s *Size) Set(str string) error {
	n, err := strconv.ParseInt(str, 10, 64)
	if err != nil {
		return err
	}
	*s = Size(n)
	return nil
}

// SizeToString pretty prints file size (given as number of bytes).
func SizeToString(s int64) string {
	v := float64(s)
	i := 0
	for ; i < len(units); i++ {
		if v < 1024. {
			break
		}
		v /= 1024.
	}
	if i == 0 {
		return fmt.Sprintf("%d%s", s, units[i])
	}
	if v >= 10 {
		return fmt.Sprintf("%.1f%s", v, units[i])
	}
	return fmt.Sprintf("%.2f%s", v, units[i])
}