webpush-apn-relay/iOS/Decode85.swift

import Foundation

private let DecodeTable: [UInt32] = [
	0xff, 0x44, 0xff, 0x54, 0x53, 0x52, 0x48, 0xff,
	0x4b, 0x4c, 0x46, 0x41, 0xff, 0x3f, 0x3e, 0x45,
	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
	0x08, 0x09, 0x40, 0xff, 0x49, 0x42, 0x4a, 0x47,
	0x51, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a,
	0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32,
	0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a,
	0x3b, 0x3c, 0x3d, 0x4d, 0xff, 0x4e, 0x43, 0xff,
	0xff, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
	0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
	0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
	0x21, 0x22, 0x23, 0x4f, 0xff, 0x50, 0xff, 0xff
]

extension String {
	func decode85() -> Data {
		var data = Data()
		var block: UInt32 = 0
		var n = 0
		for c in utf8 {
			if c >= 32, c < 128, DecodeTable[Int(c - 32)] != 0xff {
				let value = DecodeTable[Int(c - 32)]
				block = block * 85 + value
				n += 1
				if n == 5 {
					data.append(UInt8(block >> 24))
					data.append(UInt8((block >> 16) & 0xff))
					data.append(UInt8((block >> 8) & 0xff))
					data.append(UInt8(block & 0xff))
					block = 0
					n = 0
				}
			}
		}

		if n >= 4 { data.append(UInt8((block >> 16) & 0xff)) }
		if n >= 3 { data.append(UInt8((block >> 8) & 0xff)) }
		if n >= 2 { data.append(UInt8(block & 0xff)) }

		return data
	}
}