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Merge pull request #73 from apple/base64url
Add base64url helper methods for Array/ArraySlice of [UInt8]
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‎Sources/TSCBasic/Base64URL.swift‎

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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2020 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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import Foundation
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extension ArraySlice where Element == UInt8 {
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/// String representation of a Base64URL-encoded `ArraySlice<UInt8>`.
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public func base64URL() -> String {
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return base64URL(prepending: [])
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}
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public func base64URL(prepending: [UInt8]) -> String {
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var offset = 0
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var recorded = 0
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let base64URLCount = ((count * 4 / 3) + 3) & ~3
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var arr = [UInt8](repeating: UInt8(ascii: "="), count: prepending.count + base64URLCount)
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self.withUnsafeBytes { from in
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arr.withUnsafeMutableBytes { to_ in
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var to = Base64URLAppendable(to_.baseAddress!)
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to.append(prepending)
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while true {
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switch self.count - offset {
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case let n where n >= 3:
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to.add = from[offset] >> 2
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to.add = from[offset] << 4 | from[offset+1] >> 4
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to.add = from[offset+1] << 2 | from[offset+2] >> 6
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to.add = from[offset+2]
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offset += 3
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recorded += 4
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case 2:
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to.add = from[offset] >> 2
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to.add = from[offset] << 4 | from[offset+1] >> 4
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to.add = from[offset+1] << 2
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recorded += 4
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return
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case 1:
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to.add = from[offset] >> 2
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to.add = from[offset] << 4
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recorded += 4
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return
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case 0:
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return
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default:
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fatalError("can't appear here (left=\(self.count-offset))")
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}
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}
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}
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}
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assert(prepending.count + recorded == arr.count, "prepending=\(prepending.count)+recorded=\(recorded) != \(arr.count)")
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return String(bytes: arr, encoding: .ascii)!
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}
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fileprivate struct Base64URLAppendable {
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private let ptr: UnsafeMutableRawPointer
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private var offset_: Int = 0
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private static let toBase64Table: [UInt8] = Array("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".utf8)
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var offset: Int {
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return offset_
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}
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init(_ ptr: UnsafeMutableRawPointer) {
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self.ptr = ptr
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}
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var add: UInt8 {
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get { return 0 }
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set {
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let value: UInt8 = Base64URLAppendable.toBase64Table[Int(newValue & 0x3f)]
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ptr.storeBytes(of: value, toByteOffset: offset_, as: UInt8.self)
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offset_ += 1
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}
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}
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mutating func append(_ bytes: [UInt8]) {
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bytes.withUnsafeBytes { arg in
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let fromptr = arg.baseAddress!
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ptr.copyMemory(from: fromptr, byteCount: bytes.count)
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}
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offset_ += bytes.count
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}
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}
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}
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extension Array where Element == UInt8 {
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/// String representation of a Base64URL-encoded `[UInt8]`.
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public func base64URL() -> String {
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return ArraySlice(self).base64URL()
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}
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/// Base64URL encoding. Returns `nil` if the Base64URL encoding is broken.
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public init?(base64URL str: String, prepending: [UInt8] = []) {
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guard let array = [UInt8](base64URL: str[str.startIndex...]) else {
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return nil
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}
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self = array
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}
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public init?(base64URL str: Substring, prepending: [UInt8] = []) {
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var memory = [UInt8](prepending)
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memory.reserveCapacity(prepending.count + str.count * 3 / 4)
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var currentValue: UInt32 = 0
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var currentBits = 0
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for char in str.unicodeScalars {
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guard char.isASCII else {
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return nil
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}
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switch char.value {
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case let n where n >= UInt32(UInt8(ascii: "A")) && n <= UInt32(UInt8(ascii: "Z")):
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currentValue <<= 6
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currentValue |= n - UInt32(UInt8(ascii: "A"))
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currentBits += 6
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case let n where n >= UInt32(UInt8(ascii: "a")) && n <= UInt32(UInt8(ascii: "z")):
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currentValue <<= 6
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currentValue |= 26 + (n - UInt32(UInt8(ascii: "a")))
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currentBits += 6
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case let n where n >= UInt32(UInt8(ascii: "0")) && n <= UInt32(UInt8(ascii: "9")):
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currentValue <<= 6
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currentValue |= 52 + (n - UInt32(UInt8(ascii: "0")))
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currentBits += 6
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case UInt32(UInt8(ascii: "-")):
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currentValue <<= 6
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currentValue |= 62
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currentBits += 6
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case UInt32(UInt8(ascii: "_")):
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currentValue <<= 6
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currentValue |= 63
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currentBits += 6
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case UInt32(UInt8(ascii: "=")):
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guard currentValue == 0 else {
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return nil
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}
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currentBits = 0
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continue
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default:
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return nil
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}
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if currentBits >= 8 {
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currentBits -= 8
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assert(currentBits < 8)
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let byte: UInt8 = UInt8(currentValue >> currentBits)
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currentValue &= (1 << currentBits) - 1
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memory.append(byte)
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}
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}
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guard currentBits == 0 && currentValue == 0 else {
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return nil
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}
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self = memory
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}
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}

‎Tests/TSCBasicTests/Base64URLTests.swift‎

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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2020 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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import XCTest
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import TSCBasic
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class Base64URLTests: XCTestCase {
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func testEncode() {
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XCTAssertEqual([UInt8]([]).base64URL(), "")
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XCTAssertEqual([UInt8]([65]).base64URL(), "QQ==")
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XCTAssertEqual([UInt8]([65, 65]).base64URL(), "QUE=")
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XCTAssertEqual([UInt8]([65, 65, 65]).base64URL(), "QUFB")
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}
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func testDecode() {
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XCTAssertEqual([UInt8](base64URL: ""), [])
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XCTAssertEqual([UInt8](base64URL: "QQ=="), [65])
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XCTAssertEqual([UInt8](base64URL: "QUE="), [65, 65])
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XCTAssertEqual([UInt8](base64URL: "QUFB"), [65, 65, 65])
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XCTAssertEqual([UInt8](base64URL: "dGVzdGluZwo="),
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[0x74, 0x65, 0x73, 0x74, 0x69, 0x6e, 0x67, 0x0a])
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}
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func testRoundTrip() {
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for count in 1...10 {
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for _ in 0...100 {
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var data = [UInt8](repeating: 0, count: count)
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for n in 0..<count {
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data[n] = UInt8.random(in: 0...UInt8.max)
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}
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let encoded = data.base64URL()
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let decoded = [UInt8](base64URL: encoded[encoded.startIndex...])
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XCTAssertEqual(data, decoded)
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}
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}
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}
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}

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