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Base64.swift
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Base64.swift
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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftNIO open source project
//
// Copyright (c) 2017-2018 Apple Inc. and the SwiftNIO project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
// This is a simplified vendored version from:
// https://github.com/fabianfett/swift-base64-kit
extension String {
/// Base64 encode a collection of UInt8 to a string, without the use of Foundation.
init<Buffer: Collection>(base64Encoding bytes: Buffer)
where Buffer.Element == UInt8
{
self = Base64.encode(bytes: bytes)
}
}
fileprivate struct Base64 {
static func encode<Buffer: Collection>(bytes: Buffer)
-> String where Buffer.Element == UInt8
{
// In Base64, 3 bytes become 4 output characters, and we pad to the
// nearest multiple of four.
let newCapacity = ((bytes.count + 2) / 3) * 4
let alphabet = Base64.encodeBase64
// NOTE: Once SE-263 lands we should replace this implementation with one
// that makes use of the non copy initializer. For more information
// please see:
// https://github.com/apple/swift-evolution/blob/master/proposals/0263-string-uninitialized-initializer.md
var outputBytes = [UInt8]()
outputBytes.reserveCapacity(newCapacity)
var input = bytes.makeIterator()
while let firstByte = input.next() {
let secondByte = input.next()
let thirdByte = input.next()
let firstChar = Base64.encode(alphabet: alphabet, firstByte: firstByte)
let secondChar = Base64.encode(alphabet: alphabet, firstByte: firstByte, secondByte: secondByte)
let thirdChar = Base64.encode(alphabet: alphabet, secondByte: secondByte, thirdByte: thirdByte)
let forthChar = Base64.encode(alphabet: alphabet, thirdByte: thirdByte)
outputBytes.append(firstChar)
outputBytes.append(secondChar)
outputBytes.append(thirdChar)
outputBytes.append(forthChar)
}
return String(decoding: outputBytes, as: Unicode.UTF8.self)
}
// MARK: Internal
// The base64 unicode table.
static let encodeBase64: [UInt8] = [
UInt8(ascii: "A"), UInt8(ascii: "B"), UInt8(ascii: "C"), UInt8(ascii: "D"),
UInt8(ascii: "E"), UInt8(ascii: "F"), UInt8(ascii: "G"), UInt8(ascii: "H"),
UInt8(ascii: "I"), UInt8(ascii: "J"), UInt8(ascii: "K"), UInt8(ascii: "L"),
UInt8(ascii: "M"), UInt8(ascii: "N"), UInt8(ascii: "O"), UInt8(ascii: "P"),
UInt8(ascii: "Q"), UInt8(ascii: "R"), UInt8(ascii: "S"), UInt8(ascii: "T"),
UInt8(ascii: "U"), UInt8(ascii: "V"), UInt8(ascii: "W"), UInt8(ascii: "X"),
UInt8(ascii: "Y"), UInt8(ascii: "Z"), UInt8(ascii: "a"), UInt8(ascii: "b"),
UInt8(ascii: "c"), UInt8(ascii: "d"), UInt8(ascii: "e"), UInt8(ascii: "f"),
UInt8(ascii: "g"), UInt8(ascii: "h"), UInt8(ascii: "i"), UInt8(ascii: "j"),
UInt8(ascii: "k"), UInt8(ascii: "l"), UInt8(ascii: "m"), UInt8(ascii: "n"),
UInt8(ascii: "o"), UInt8(ascii: "p"), UInt8(ascii: "q"), UInt8(ascii: "r"),
UInt8(ascii: "s"), UInt8(ascii: "t"), UInt8(ascii: "u"), UInt8(ascii: "v"),
UInt8(ascii: "w"), UInt8(ascii: "x"), UInt8(ascii: "y"), UInt8(ascii: "z"),
UInt8(ascii: "0"), UInt8(ascii: "1"), UInt8(ascii: "2"), UInt8(ascii: "3"),
UInt8(ascii: "4"), UInt8(ascii: "5"), UInt8(ascii: "6"), UInt8(ascii: "7"),
UInt8(ascii: "8"), UInt8(ascii: "9"), UInt8(ascii: "+"), UInt8(ascii: "/"),
]
static let encodePaddingCharacter: UInt8 = UInt8(ascii: "=")
static func encode(alphabet: [UInt8], firstByte: UInt8) -> UInt8 {
let index = firstByte >> 2
return alphabet[Int(index)]
}
static func encode(alphabet: [UInt8], firstByte: UInt8, secondByte: UInt8?) -> UInt8 {
var index = (firstByte & 0b00000011) << 4
if let secondByte = secondByte {
index += (secondByte & 0b11110000) >> 4
}
return alphabet[Int(index)]
}
static func encode(alphabet: [UInt8], secondByte: UInt8?, thirdByte: UInt8?) -> UInt8 {
guard let secondByte = secondByte else {
// No second byte means we are just emitting padding.
return Base64.encodePaddingCharacter
}
var index = (secondByte & 0b00001111) << 2
if let thirdByte = thirdByte {
index += (thirdByte & 0b11000000) >> 6
}
return alphabet[Int(index)]
}
static func encode(alphabet: [UInt8], thirdByte: UInt8?) -> UInt8 {
guard let thirdByte = thirdByte else {
// No third byte means just padding.
return Base64.encodePaddingCharacter
}
let index = thirdByte & 0b00111111
return alphabet[Int(index)]
}
}