random.go

package testutil

import (
	"math/rand"
	"strings"
	"unicode/utf8"
)

// RandomRune returns a random Unicode rune from rand, weighting at least
// num out of den runes to be ASCII.
func RandomRune(rand *rand.Rand, num, den int) rune {
	if rand.Intn(den) < num {
		return rune(rand.Intn(utf8.RuneSelf))
	}
	for {
		r := rune(rand.Intn(utf8.MaxRune))
		// Almost all chars are legal, so this usually
		// returns immediately.
		if utf8.ValidRune(r) {
			return r
		}
	}
}

// RandomString returns a random UTF-8 string of size or almost size bytes
// from rand.  It is weighted towards using many ASCII characters.
func RandomString(rand *rand.Rand, size int) string {
	sb := strings.Builder{}
	for sb.Len() <= size {
		sb.WriteRune(RandomRune(rand, 2, 5)) //nolint: gomnd
	}
	ret := sb.String()
	_, lastRuneSize := utf8.DecodeLastRuneInString(ret)
	return ret[0 : len(ret)-lastRuneSize]
}