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92 lines
3.7 KiB
Swift
92 lines
3.7 KiB
Swift
//
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// LZMA.swift
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// SWCompression
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//
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// Created by Timofey Solomko on 15.12.16.
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// Copyright © 2017 Timofey Solomko. All rights reserved.
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//
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import Foundation
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/**
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Error happened during LZMA decompression.
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It may indicate that either the data is damaged or it might not be compressed with LZMA at all.
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- `wrongProperties`: unsupported LZMA properties (greater than 225).
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- `rangeDecoderInitError`: unable to initialize RangedDecoder.
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- `exceededUncompressedSize`: the number of uncompressed bytes reached amount specified by archive
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while decoding wasn't finished.
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- `windowIsEmpty`: unable to repeat bytes because there is nothing to repeat.
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- `rangeDecoderFinishError`: range decoder was in a bad state when finish marker was reached.
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- `repeatWillExceed`: unable to repeat bytes because the number of bytes to repeat is greater
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than the amount bytes that is left to decode.
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- `notEnoughToRepeat`: unable to repeat bytes because the amount of already decoded bytes is smaller
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than the repeat length.
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*/
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public enum LZMAError: Error {
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/// Properties byte was greater than 225.
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case wrongProperties
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/// Unable to initialize RanderDecorer.
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case rangeDecoderInitError
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/// The number of uncompressed bytes hit limit in the middle of decoding.
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case exceededUncompressedSize
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/// Unable to perfrom repeat-distance decoding because there is nothing to repeat.
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case windowIsEmpty
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/// End of stream marker is reached, but range decoder is in incorrect state.
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case rangeDecoderFinishError
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/// The number of bytes to repeat is greater than the amount bytes that is left to decode.
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case repeatWillExceed
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/// The amount of already decoded bytes is smaller than repeat length.
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case notEnoughToRepeat
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}
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/// Provides function to decompress data, which were compressed with LZMA
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public final class LZMA: DecompressionAlgorithm {
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/**
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Decompresses `compressedData` with LZMA algortihm.
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If data passed is not actually compressed with LZMA, `LZMAError` will be thrown.
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- Parameter compressedData: Data compressed with LZMA.
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- Throws: `LZMAError` if unexpected byte (bit) sequence was encountered in `compressedData`.
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It may indicate that either the data is damaged or it might not be compressed with LZMA at all.
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- Returns: Decompressed data.
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*/
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public static func decompress(compressedData data: Data) throws -> Data {
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/// Object with input data which supports convenient work with bit shifts.
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var pointerData = DataWithPointer(data: data, bitOrder: .reversed)
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return Data(bytes: try decompress(&pointerData))
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}
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static func decompress(_ pointerData: inout DataWithPointer) throws -> [UInt8] {
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// Firstly, we need to parse LZMA properties.
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var properties = pointerData.alignedByte()
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if properties >= (9 * 5 * 5) {
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throw LZMAError.wrongProperties
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}
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/// The number of literal context bits
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let lc = properties % 9
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properties /= 9
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/// The number of pos bits
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let pb = properties / 5
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/// The number of literal pos bits
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let lp = properties % 5
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var dictionarySize = pointerData.intFromAlignedBytes(count: 4)
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dictionarySize = dictionarySize < (1 << 12) ? 1 << 12 : dictionarySize
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/// Size of uncompressed data. -1 means it is unknown/undefined.
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var uncompressedSize = pointerData.intFromAlignedBytes(count: 8)
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uncompressedSize = Double(uncompressedSize) == pow(Double(2), Double(64)) - 1 ? -1 : uncompressedSize
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let lzmaDecoder = try LZMADecoder(&pointerData, lc, pb, lp, dictionarySize)
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try lzmaDecoder.decodeLZMA(&uncompressedSize)
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return lzmaDecoder.out
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}
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}
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