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- separate parsing into Bencoder class - throw custom errors at parsing
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| // | ||
| // Bencoder.swift | ||
| // Bencode | ||
| // | ||
| // Created by Daniel Tombor on 2018. 04. 30.. | ||
| // | ||
|
|
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| import Foundation | ||
|
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| final class Bencoder { | ||
|
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| // MARK: - Constants | ||
|
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| private struct Tokens { | ||
| let i: UInt8 = 0x69 | ||
| let l: UInt8 = 0x6c | ||
| let d: UInt8 = 0x64 | ||
| let e: UInt8 = 0x65 | ||
| let zero: UInt8 = 0x30 | ||
| let nine: UInt8 = 0x39 | ||
| let colon: UInt8 = 0x3a | ||
| } | ||
|
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| private let tokens = Tokens() | ||
|
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| // MARK: - Methods | ||
|
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| /** Decoding from Bencoded string */ | ||
| func decode(bencodedString str: String) throws -> Bencode { | ||
| return try decode(bytes: str.ascii) | ||
| } | ||
|
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| /** Decoding bencoded file */ | ||
| func decode(file url: URL) throws -> Bencode { | ||
| let data = try Data(contentsOf: url) | ||
| return try decode(bytes: [Byte](data)) | ||
| } | ||
|
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| /** Decoding from bytes */ | ||
| func decode(bytes: [UInt8]) throws -> Bencode { | ||
| return try parse(bytes).bencode | ||
| } | ||
|
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| /** Encoding to Bencode string */ | ||
| func encoded(bencode: Bencode) -> String { | ||
| switch bencode { | ||
| case .integer(let i): return "i\(i)e" | ||
| case .string(let b): return "\(b.count):\(String(bytes: b, encoding: .ascii)!)" | ||
| case .list(let l): | ||
| let desc = l.map { $0.encoded }.joined() | ||
| return "l\(desc)e" | ||
| case .dictionary(let d): | ||
| let desc = d.sorted(by: { $0.key < $1.key }) | ||
| .map { "\(Bencode.string($0.key.ascii).encoded)\($1.encoded)" } | ||
| .joined() | ||
| return "d\(desc)e" | ||
| } | ||
| } | ||
|
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| /** Encoding to Bencoded Data */ | ||
| func asciiEncoding(bencode: Bencode) -> Data { | ||
| return Data(bytes: encoded(bencode: bencode).ascii) | ||
| } | ||
| } | ||
|
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| // MARK: - Private decoding helpers | ||
|
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| private extension Bencoder { | ||
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| typealias ParseResult = (bencode: Bencode, index: Int) | ||
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| func parse(_ data: [Byte]) throws -> ParseResult { | ||
| return try parse(ArraySlice(data), from: 0) | ||
| } | ||
|
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| func parse(_ data: ArraySlice<Byte>, from index: Int) throws -> ParseResult { | ||
| guard data.endIndex >= index + 1 | ||
| else { throw BencoderError.indexOutOfBounds(end: data.endIndex, current: index + 1) } | ||
|
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| let nextIndex = index+1 | ||
| let nextSlice = data[nextIndex...] | ||
|
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| switch data[index] { | ||
| case tokens.i: return try parseInt(nextSlice, from: nextIndex) | ||
| case tokens.zero...tokens.nine: return try parseString(data, from: index) | ||
| case tokens.l: return try parseList(nextSlice, from: nextIndex) | ||
| case tokens.d: return try parseDictionary(nextSlice, from: nextIndex) | ||
| default: throw BencoderError.unknownToken(data[index]) | ||
| } | ||
| } | ||
|
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| func parseInt(_ data: ArraySlice<Byte>, from index: Int) throws -> ParseResult { | ||
| guard let end = data.index(of: tokens.e) | ||
| else { throw BencoderError.tokenNotFound(tokens.e) } | ||
| guard let num = Array(data[..<end]).int | ||
| else { throw BencoderError.invalidNumber } | ||
| return (bencode: .integer(num), index: end+1) | ||
| } | ||
|
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| func parseString(_ data: ArraySlice<Byte>, from index: Int) throws -> ParseResult { | ||
| guard let sep = data.index(of: tokens.colon) | ||
| else { throw BencoderError.tokenNotFound(tokens.colon) } | ||
| guard let len = Array(data[..<sep]).int | ||
| else { throw BencoderError.invalidNumber } | ||
| let start = sep + 1 | ||
| let end = data.index(start, offsetBy: len) | ||
| return (bencode: .string(Array(data[start..<end])), index: end) | ||
| } | ||
|
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| func parseList(_ data: ArraySlice<Byte>, from index: Int) throws -> ParseResult { | ||
| var l: [Bencode] = [] | ||
| var idx: Int = index | ||
|
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| while data[idx] != tokens.e { | ||
| let result = try parse(data[idx...], from: idx) | ||
| l.append(result.bencode) | ||
| idx = result.index | ||
| } | ||
| return (bencode: .list(l), index: idx+1) | ||
| } | ||
|
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| func parseDictionary(_ data: ArraySlice<Byte>, from index: Int) throws -> ParseResult { | ||
| var d: [BencodeKey:Bencode] = [:] | ||
| var idx: Int = index | ||
| var order = 0 | ||
|
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| while data[idx] != tokens.e { | ||
| let keyResult = try parseString(data[idx...], from: idx) | ||
| guard case .string(let keyData) = keyResult.bencode, | ||
| let key = keyData.string | ||
| else { throw BencoderError.unexpectedKey(keyResult.bencode) } | ||
| let valueResult = try parse(data[keyResult.index...], from: keyResult.index) | ||
| d[BencodeKey(key, order: order)] = valueResult.bencode | ||
| idx = valueResult.index | ||
| order += 1 | ||
| } | ||
| return (bencode: .dictionary(d), index: idx+1) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,16 @@ | ||
| // | ||
| // BencoderError.swift | ||
| // Bencode | ||
| // | ||
| // Created by Daniel Tombor on 2018. 04. 30.. | ||
| // | ||
|
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| import Foundation | ||
|
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| enum BencoderError: Error { | ||
| case unknownToken(UInt8) | ||
| case tokenNotFound(UInt8) | ||
| case unexpectedKey(Bencode) | ||
| case invalidNumber | ||
| case indexOutOfBounds(end: Int, current: Int) | ||
| } |
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