util.go を追加する

util.go

@@ -0,0 +1,75 @@
+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+// Package util provides auxiliary functions internally used in webrtc package
+package suzu
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/pion/randutil"
+)
+
+const (
+	runesAlpha = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+)
+
+// Use global random generator to properly seed by crypto grade random.
+var globalMathRandomGenerator = randutil.NewMathRandomGenerator() // nolint:gochecknoglobals
+
+// MathRandAlpha generates a mathematical random alphabet sequence of the requested length.
+func MathRandAlpha(n int) string {
+	return globalMathRandomGenerator.GenerateString(n, runesAlpha)
+}
+
+// RandUint32 generates a mathematical random uint32.
+func RandUint32() uint32 {
+	return globalMathRandomGenerator.Uint32()
+}
+
+// FlattenErrs flattens multiple errors into one
+func FlattenErrs(errs []error) error {
+	errs2 := []error{}
+	for _, e := range errs {
+		if e != nil {
+			errs2 = append(errs2, e)
+		}
+	}
+	if len(errs2) == 0 {
+		return nil
+	}
+	return multiError(errs2)
+}
+
+type multiError []error //nolint:errname
+
+func (me multiError) Error() string {
+	var errstrings []string
+
+	for _, err := range me {
+		if err != nil {
+			errstrings = append(errstrings, err.Error())
+		}
+	}
+
+	if len(errstrings) == 0 {
+		return "multiError must contain multiple error but is empty"
+	}
+
+	return strings.Join(errstrings, "\n")
+}
+
+func (me multiError) Is(err error) bool {
+	for _, e := range me {
+		if errors.Is(e, err) {
+			return true
+		}
+		if me2, ok := e.(multiError); ok { //nolint:errorlint
+			if me2.Is(err) {
+				return true
+			}
+		}
+	}
+	return false
+}