commonMain.com.twilio.passkeys.extensions.StringExtensions.kt Maven / Gradle / Ivy

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Twilio Passkeys SDK enables developers to easily add Passkeys into their existing authentication flows within their own mobile applications. The Verify Passkeys SDK supports passkeys creation and authentication using the FIDO/WebAuthn industry standard.

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/*
 * Copyright © 2024 Twilio Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.twilio.passkeys.extensions

import kotlin.io.encoding.Base64
import kotlin.io.encoding.ExperimentalEncodingApi

/**
 * Decodes the Base64-encoded string using URL-safe decoding into a byte array.
 *
 * @receiver The Base64-encoded string to be decoded.
 * @return The decoded byte array.
 */
@OptIn(ExperimentalEncodingApi::class)
internal fun String.b64Decode(): ByteArray {
  return Base64.UrlSafe.decode(this.padBase64())
}

private const val BASE64_BLOCK_SIZE = 4
private const val NO_PADDING_NEEDED = 0

// Helper function to pad the Base64 string if needed
private fun String.padBase64(): String {
  val missingPadding = this.length % BASE64_BLOCK_SIZE
  return if (missingPadding == NO_PADDING_NEEDED) this else this + "=".repeat(BASE64_BLOCK_SIZE - missingPadding)
}