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