everettcaleb/envconfig

package envconfig

import (
    "fmt"
    "reflect"
    "strings"
)

// getStructTagAsBool gets a struct tag (by name) as a boolean or returns a default value if not specified
func getStructTagAsBool(f *reflect.StructField, tag string, defaultValue bool) (bool, error) {
    str, ok := f.Tag.Lookup(tag)
    if ok {
        v, err := parseFriendlyBool(str)
        if err != nil {
            return false, fmt.Errorf("Tag %s must have boolean string value", tag)
        }
        return v, nil
    }
    return defaultValue, nil
}

// bitsOf gets the number of bits of the reflected variable kind
func bitsOf(k reflect.Kind) int {
    switch k {
    case reflect.Int8, reflect.Uint8:
        return 8
    case reflect.Int16, reflect.Uint16:
        return 16
    case reflect.Float32, reflect.Int32, reflect.Uint32:
        return 32
    case reflect.Float64, reflect.Int, reflect.Int64, reflect.Uint, reflect.Uint64:
        return 64
    default:
        return 0
    }
}

// parseFriendlyBool parses a multitude of values as boolean case-insensitively: "yes"/"no", "true"/"false", "on"/"off",
// "t"/"f", "y"/"n", "1"/"0" to allow for more expressive configuration settings
func parseFriendlyBool(s string) (bool, error) {
    switch strings.ToLower(s) {
    case "yes", "true", "on", "t", "y", "1":
        return true, nil
    case "no", "false", "off", "f", "n", "0":
        return false, nil
    default:
        return false, fmt.Errorf("Expected boolean value, got: %s", s)
    }
}