70 lines
2.7 KiB
Swift
70 lines
2.7 KiB
Swift
//
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// Alphabet.swift
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// Bases
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//
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// Copyright (c) 2015-2018 Matt Rubin and the Bases authors
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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//
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internal typealias EncodedChar = UInt8
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// Each 5-bit group is used as an index into an array of 32 printable
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// characters. The character referenced by the index is placed in the
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// output string. These characters, identified in Table 3, below, are
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// selected from US-ASCII digits and uppercase letters.
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//
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// Table 3: The Base 32 Alphabet
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//
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// Value Encoding Value Encoding Value Encoding Value Encoding
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// 0 A 9 J 18 S 27 3
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// 1 B 10 K 19 T 28 4
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// 2 C 11 L 20 U 29 5
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// 3 D 12 M 21 V 30 6
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// 4 E 13 N 22 W 31 7
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// 5 F 14 O 23 X
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// 6 G 15 P 24 Y (pad) =
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// 7 H 16 Q 25 Z
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// 8 I 17 R 26 2
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internal let paddingCharacter: EncodedChar = 61
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private let encodingTable: [EncodedChar] = [
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65, 66, 67, 68, 69, 70, 71, 72,
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73, 74, 75, 76, 77, 78, 79, 80,
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81, 82, 83, 84, 85, 86, 87, 88,
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89, 90, 50, 51, 52, 53, 54, 55,
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]
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internal func character(encoding quintet: Quintet) -> EncodedChar {
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return encodingTable[Int(quintet)]
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}
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internal func quintet(decoding char: EncodedChar) throws -> Quintet {
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switch char {
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case 50...55:
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return char - 24
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case 65...90:
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return char - 65
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case 97...122:
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return char - 97
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default:
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throw Base32.Error.nonAlphabetCharacter
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}
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}
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