source: code/trunk/vendor/gopkg.in/yaml.v2/sorter.go@ 67

package yaml

import (
        "reflect"
        "unicode"
)

type keyList []reflect.Value

func (l keyList) Len() int      { return len(l) }
func (l keyList) Swap(i, j int) { l[i], l[j] = l[j], l[i] }
func (l keyList) Less(i, j int) bool {
        a := l[i]
        b := l[j]
        ak := a.Kind()
        bk := b.Kind()
        for (ak == reflect.Interface || ak == reflect.Ptr) && !a.IsNil() {
                a = a.Elem()
                ak = a.Kind()
        }
        for (bk == reflect.Interface || bk == reflect.Ptr) && !b.IsNil() {
                b = b.Elem()
                bk = b.Kind()
        }
        af, aok := keyFloat(a)
        bf, bok := keyFloat(b)
        if aok && bok {
                if af != bf {
                        return af < bf
                }
                if ak != bk {
                        return ak < bk
                }
                return numLess(a, b)
        }
        if ak != reflect.String || bk != reflect.String {
                return ak < bk
        }
        ar, br := []rune(a.String()), []rune(b.String())
        for i := 0; i < len(ar) && i < len(br); i++ {
                if ar[i] == br[i] {
                        continue
                }
                al := unicode.IsLetter(ar[i])
                bl := unicode.IsLetter(br[i])
                if al && bl {
                        return ar[i] < br[i]
                }
                if al || bl {
                        return bl
                }
                var ai, bi int
                var an, bn int64
                if ar[i] == '0' || br[i] == '0' {
                        for j := i-1; j >= 0 && unicode.IsDigit(ar[j]); j-- {
                                if ar[j] != '0' {
                                        an = 1
                                        bn = 1
                                        break
                                }
                        }
                }
                for ai = i; ai < len(ar) && unicode.IsDigit(ar[ai]); ai++ {
                        an = an*10 + int64(ar[ai]-'0')
                }
                for bi = i; bi < len(br) && unicode.IsDigit(br[bi]); bi++ {
                        bn = bn*10 + int64(br[bi]-'0')
                }
                if an != bn {
                        return an < bn
                }
                if ai != bi {
                        return ai < bi
                }
                return ar[i] < br[i]
        }
        return len(ar) < len(br)
}

// keyFloat returns a float value for v if it is a number/bool
// and whether it is a number/bool or not.
func keyFloat(v reflect.Value) (f float64, ok bool) {
        switch v.Kind() {
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
                return float64(v.Int()), true
        case reflect.Float32, reflect.Float64:
                return v.Float(), true
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
                return float64(v.Uint()), true
        case reflect.Bool:
                if v.Bool() {
                        return 1, true
                }
                return 0, true
        }
        return 0, false
}

// numLess returns whether a < b.
// a and b must necessarily have the same kind.
func numLess(a, b reflect.Value) bool {
        switch a.Kind() {
        case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
                return a.Int() < b.Int()
        case reflect.Float32, reflect.Float64:
                return a.Float() < b.Float()
        case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
                return a.Uint() < b.Uint()
        case reflect.Bool:
                return !a.Bool() && b.Bool()
        }
        panic("not a number")
}