add vendoring

vendor/maunium.net/go/mautrix/util/random.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2022 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package util
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"hash/crc32"
+	"strings"
+	"unsafe"
+)
+
+func RandomBytes(n int) []byte {
+	data := make([]byte, n)
+	_, err := rand.Read(data)
+	if err != nil {
+		panic(err)
+	}
+	return data
+}
+
+var letters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+// RandomString generates a random string of the given length.
+func RandomString(n int) string {
+	if n <= 0 {
+		return ""
+	}
+	base64Len := n
+	if n%4 != 0 {
+		base64Len += 4 - (n % 4)
+	}
+	decodedLength := base64.RawStdEncoding.DecodedLen(base64Len)
+	output := make([]byte, base64Len)
+	base64.RawStdEncoding.Encode(output, RandomBytes(decodedLength))
+	for i, char := range output {
+		if char == '+' || char == '/' {
+			_, err := rand.Read(output[i : i+1])
+			if err != nil {
+				panic(err)
+			}
+			output[i] = letters[int(output[i])%len(letters)]
+		}
+	}
+	return (*(*string)(unsafe.Pointer(&output)))[:n]
+}
+
+func base62Encode(val uint32, minWidth int) string {
+	var buf strings.Builder
+	for val > 0 {
+		buf.WriteByte(letters[val%62])
+		val /= 62
+	}
+	return strings.Repeat("0", minWidth-buf.Len()) + buf.String()
+}
+
+func RandomToken(namespace string, randomLength int) string {
+	token := namespace + "_" + RandomString(randomLength)
+	checksum := base62Encode(crc32.ChecksumIEEE([]byte(token)), 6)
+	return token + "_" + checksum
+}