mirror of
https://github.com/tsolomko/SWCompression.git
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Timofey Solomko
513 lines
22 KiB
Swift
513 lines
22 KiB
Swift
//
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// ZipContainer.swift
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// SWCompression
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//
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// Created by Timofey Solomko on 14.01.17.
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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 processing ZIP archive (container).
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It may indicate that either the data is damaged or it might not be ZIP archive (container) at all.
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- `NotFoundCentralDirectoryEnd`: end of Central Directoty record wasn't found.
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- `WrongSignature`: unsupported signature of one of ZIP container's structures.
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- `WrongSize`: incorrect compressed or uncompressed size of a ZIP container's entry's data.
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- `WrongVersion`: unsupported number of version needed to extract ZIP container
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(unsupported features are required to open this file).
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- `MultiVolumesNotSupported`: unsupported feature: multi-volumed or spanned container.
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- `EncryptionNotSupported`: unsupported feature: encryption.
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- `PatchingNotSupported`: unsupported feature: patched data.
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- `CompressionNotSupported`: unsupported feature: specified compression method.
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- `WrongLocalHeader`: local header of an entry wasn't consistent with Central Directory record.
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- `WrongCRC32`: computed checksum of entry's data wasn't the same as the one stored in container.
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*/
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public enum ZipError: Error {
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/// End of Central Directoty record was not found.
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case NotFoundCentralDirectoryEnd
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/// Wrong signature of one of ZIP container's structures.
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case WrongSignature
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/// Wrong either compressed or uncompressed size of a ZIP container's entry.
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case WrongSize
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/// Wrong number of version needed to extract ZIP container.
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case WrongVersion
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/// Archive either spanned or consists of several volumes. This feature is not supported.
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case MultiVolumesNotSupported
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/// Entry or record is encrypted. This feature is not supported.
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case EncryptionNotSupported
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/// Entry contains patched data. This feature is not supported.
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case PatchingNotSupported
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/// Wrong compression method of an entry.
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case CompressionNotSupported
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/// Wrong local header of an entry.
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case WrongLocalHeader
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/// Wrong computed CRC32 of an entry.
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case WrongCRC32
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}
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/// Represents either a file or directory entry inside ZIP archive.
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public struct ZipEntry {
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fileprivate let cdEntry: CentralDirectoryEntry
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/// Name of the file or directory.
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public var fileName: String? {
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return self.cdEntry.fileComment
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}
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/// Comment associated with the entry.
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public var fileComment: String? {
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return self.cdEntry.fileComment
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}
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/// File or directory attributes related to the file system of archive's creator.
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public var fileAttributes: UInt32 {
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return self.cdEntry.externalFileAttributes
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}
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init(_ cdEntry: CentralDirectoryEntry) {
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self.cdEntry = cdEntry
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}
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}
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/// Provides function to open ZIP archives (containers).
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public class ZipContainer {
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private var pointerData: DataWithPointer
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/// All file and directory entries found in ZIP archive (in its Central Directory).
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public private(set) var entries: [ZipEntry]
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/**
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Tries to open ZIP archive and parse its Central Directory.
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If parsing is successful then `entries` property will contain all directory or file entries found in archive.
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- Important: The order of entries is defined by ZIP archive and, particularly, creator of given ZIP container.
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It is likely that directories will be encountered earlier than files stored in those directories,
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but one SHOULD NOT assume that this is the case.
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- Note: Currently, there is no universal (platform and file system independent) method to determine if entry is a directory.
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One can check this by looking at the size of entry's data (it should be 0 for directory) AND
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the last character of entry's name (it should be '/'). If all of these is true then entry is likely to be a directory.
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- Note: Only ZIP containers complying to ISO/IEC 21320-1 standard are supported.
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- Parameter containerData: Data of ZIP container.
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- Throws: `ZipError` or `DeflateError` depending on the type of inconsistency in data.
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It may indicate that either the container is damaged or it might not be ZIP container or compressed with Deflate at all.
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*/
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public init(containerData data: Data) throws {
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/// Object with input data which supports convenient work with bit shifts.
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self.pointerData = DataWithPointer(data: data, bitOrder: .reversed)
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self.entries = []
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pointerData.index = pointerData.size - 22 // 22 is a minimum amount which could take end of CD record.
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while true {
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// Check signature.
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if pointerData.uint64FromAlignedBytes(count: 4) == 0x06054b50 {
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// We found it!
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break
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}
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if pointerData.index == 0 {
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throw ZipError.NotFoundCentralDirectoryEnd
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}
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pointerData.index -= 5
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}
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let endOfCD = try EndOfCentralDirectory(&pointerData)
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let cdEntries = endOfCD.cdEntries
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// OK, now we are ready to read Central Directory itself.
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pointerData.index = Int(UInt(truncatingBitPattern: endOfCD.cdOffset))
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for _ in 0..<cdEntries {
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let cdEntry = try CentralDirectoryEntry(&pointerData, endOfCD.currentDiskNumber)
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self.entries.append(ZipEntry(cdEntry))
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}
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}
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/**
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Returns data associated with provided ZipEntry.
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- Note: Returned `Data` object with the size of 0 can either indicate that the entry is an empty file
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or it is a directory.
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- Parameter zipEntry: file or directory entry from current container.
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- Throws: `ZipError` or `DeflateError` depending on the type of inconsistency in data.
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An error can indicate that the container is damaged.
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*/
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public func data(for zipEntry: ZipEntry) throws -> Data {
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// Now, let's move to the location of local header.
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pointerData.index = Int(UInt32(truncatingBitPattern: zipEntry.cdEntry.offset))
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let localHeader = try LocalHeader(&pointerData)
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// Check local header for consistency with Central Directory entry.
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guard localHeader.versionNeeded <= 45 &&
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localHeader.generalPurposeBitFlags == zipEntry.cdEntry.generalPurposeBitFlags &&
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localHeader.compressionMethod == zipEntry.cdEntry.compressionMethod &&
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localHeader.lastModFileTime == zipEntry.cdEntry.lastModFileTime &&
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localHeader.lastModFileDate == zipEntry.cdEntry.lastModFileDate
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else { throw ZipError.WrongLocalHeader }
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let hasDataDescriptor = localHeader.generalPurposeBitFlags & 0x08 != 0
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// If file has data descriptor, then some values in local header are absent.
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// So we need to use values from CD entry.
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var uncompSize = hasDataDescriptor ?
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Int(UInt32(truncatingBitPattern: zipEntry.cdEntry.uncompSize)) :
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Int(UInt32(truncatingBitPattern: localHeader.uncompSize))
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var compSize = hasDataDescriptor ?
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Int(UInt32(truncatingBitPattern: zipEntry.cdEntry.compSize)) :
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Int(UInt32(truncatingBitPattern: localHeader.compSize))
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var crc32 = hasDataDescriptor ? zipEntry.cdEntry.crc32 : localHeader.crc32
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let fileBytes: [UInt8]
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let fileDataStart = pointerData.index
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switch localHeader.compressionMethod {
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case 0:
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fileBytes = pointerData.alignedBytes(count: uncompSize)
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case 8:
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fileBytes = try Deflate.decompress(&pointerData)
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// Sometimes pointerData stays in not-aligned state after deflate decompression.
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// Following line ensures that this is not the case.
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pointerData.skipUntilNextByte()
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default:
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throw ZipError.CompressionNotSupported
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}
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let realCompSize = pointerData.index - fileDataStart
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if hasDataDescriptor {
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// Now we need to parse data descriptor itself.
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// First, it might or might not have signature.
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let ddSignature = pointerData.uint64FromAlignedBytes(count: 4)
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if ddSignature != 0x08074b50 {
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pointerData.index -= 4
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}
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// Now, let's update from CD with values from data descriptor.
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crc32 = UInt32(truncatingBitPattern: pointerData.uint64FromAlignedBytes(count: 4))
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compSize = Int(UInt32(truncatingBitPattern: pointerData.uint64FromAlignedBytes(count: 4)))
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uncompSize = Int(UInt32(truncatingBitPattern: pointerData.uint64FromAlignedBytes(count: 4)))
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}
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guard compSize == realCompSize && uncompSize == fileBytes.count
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else { throw ZipError.WrongSize }
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guard crc32 == UInt32(CheckSums.crc32(fileBytes))
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else { throw ZipError.WrongCRC32 }
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return Data(bytes: fileBytes)
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}
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/**
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Processes ZIP archive (container) and returns an array of tuples `(String, Data)`.
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First member of a tuple is entry's name, second member is entry's data.
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- Important: The order of entries is defined by ZIP archive and, particularly, creator of given ZIP container.
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It is likely that directories will be encountered earlier than files stored in those directories,
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but one SHOULD NOT assume that this is the case.
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- Note: Currently, there is no universal (platform and file system independent) method to determine if entry is a directory.
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One can check this by looking at the size of entry's data (it should be 0 for directory) AND
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the last character of entry's name (it should be '/'). If all of these is true then entry is likely to be a directory.
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- Note: Only ZIP containers complying to ISO/IEC 21320-1 standard are supported.
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- Parameter containerData: Data of ZIP container.
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- Throws: `ZipError` or `DeflateError` depending on the type of inconsistency in data.
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It may indicate that either the container is damaged or it might not be ZIP container or compressed with Deflate at all.
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- Returns: Array of pairs (tuples) where first member is `entryName` and second member is `entryData`.
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*/
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public static func open(containerData data: Data) throws -> [(entryName: String, entryData: Data)] {
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let zipContainer = try ZipContainer(containerData: data)
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var result: [(String, Data)] = []
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for zipEntry in zipContainer.entries {
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result.append((zipEntry.fileName!, try zipContainer.data(for: zipEntry)))
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}
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return result
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}
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}
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struct LocalHeader {
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let versionNeeded: Int
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let generalPurposeBitFlags: Int
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let compressionMethod: Int
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let lastModFileTime: Int
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let lastModFileDate: Int
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let crc32: UInt32
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private(set) var compSize: UInt64
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private(set) var uncompSize: UInt64
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let fileName: String?
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init(_ pointerData: inout DataWithPointer) throws {
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// Check signature.
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guard pointerData.uint64FromAlignedBytes(count: 4) == 0x04034b50
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else { throw ZipError.WrongSignature }
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self.versionNeeded = pointerData.intFromAlignedBytes(count: 2)
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self.generalPurposeBitFlags = pointerData.intFromAlignedBytes(count: 2)
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self.compressionMethod = pointerData.intFromAlignedBytes(count: 2)
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self.lastModFileTime = pointerData.intFromAlignedBytes(count: 2)
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self.lastModFileDate = pointerData.intFromAlignedBytes(count: 2)
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self.crc32 = UInt32(truncatingBitPattern: pointerData.uint64FromAlignedBytes(count: 4))
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self.compSize = pointerData.uint64FromAlignedBytes(count: 4)
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self.uncompSize = pointerData.uint64FromAlignedBytes(count: 4)
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let fileNameLength = pointerData.intFromAlignedBytes(count: 2)
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let extraFieldLength = pointerData.intFromAlignedBytes(count: 2)
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self.fileName = String(data: Data(bytes: pointerData.alignedBytes(count: fileNameLength)),
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encoding: .utf8)
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let extraFieldStart = pointerData.index
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while pointerData.index - extraFieldStart < extraFieldLength {
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// There are a lot of possible extra fields.
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// But we are (currently) only interested in Zip64 related fields (with headerID = 0x0001),
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// because they directly impact further extraction process.
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let headerID = pointerData.intFromAlignedBytes(count: 2)
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let size = pointerData.intFromAlignedBytes(count: 2)
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switch headerID {
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case 0x0001:
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// In local header both uncompressed size and compressed size fields are required.
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self.uncompSize = pointerData.uint64FromAlignedBytes(count: 8)
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self.compSize = pointerData.uint64FromAlignedBytes(count: 8)
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default:
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pointerData.index += size
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}
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}
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// Let's check headers's values for consistency.
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guard self.versionNeeded <= 45
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else { throw ZipError.WrongVersion }
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guard self.generalPurposeBitFlags & 0x2000 == 0 ||
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self.generalPurposeBitFlags & 0x40 == 0 ||
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self.generalPurposeBitFlags & 0x01 == 0
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else { throw ZipError.EncryptionNotSupported }
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guard self.generalPurposeBitFlags & 0x20 == 0
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else { throw ZipError.PatchingNotSupported }
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guard self.compressionMethod == 8 || self.compressionMethod == 0
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else { throw ZipError.CompressionNotSupported }
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}
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}
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struct CentralDirectoryEntry {
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let versionMadeBy: Int
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let versionNeeded: Int
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let generalPurposeBitFlags: Int
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let compressionMethod: Int
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let lastModFileTime: Int
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let lastModFileDate: Int
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let crc32: UInt32
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private(set) var compSize: UInt64
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private(set) var uncompSize: UInt64
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let fileName: String?
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let fileComment: String?
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private(set) var diskNumberStart: UInt64
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let internalFileAttributes: Int
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let externalFileAttributes: UInt32
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private(set) var offset: UInt64
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init(_ pointerData: inout DataWithPointer, _ currentDiskNumber: UInt64) throws {
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// Check signature.
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guard pointerData.uint64FromAlignedBytes(count: 4) == 0x02014b50
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else { throw ZipError.WrongSignature }
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self.versionMadeBy = pointerData.intFromAlignedBytes(count: 2)
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self.versionNeeded = pointerData.intFromAlignedBytes(count: 2)
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self.generalPurposeBitFlags = pointerData.intFromAlignedBytes(count: 2)
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self.compressionMethod = pointerData.intFromAlignedBytes(count: 2)
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self.lastModFileTime = pointerData.intFromAlignedBytes(count: 2)
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self.lastModFileDate = pointerData.intFromAlignedBytes(count: 2)
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self.crc32 = UInt32(truncatingBitPattern: pointerData.uint64FromAlignedBytes(count: 4))
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self.compSize = pointerData.uint64FromAlignedBytes(count: 4)
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self.uncompSize = pointerData.uint64FromAlignedBytes(count: 4)
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let fileNameLength = pointerData.intFromAlignedBytes(count: 2)
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let extraFieldLength = pointerData.intFromAlignedBytes(count: 2)
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let fileCommentLength = pointerData.intFromAlignedBytes(count: 2)
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self.diskNumberStart = pointerData.uint64FromAlignedBytes(count: 2)
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self.internalFileAttributes = pointerData.intFromAlignedBytes(count: 2)
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self.externalFileAttributes = UInt32(truncatingBitPattern: pointerData.uint64FromAlignedBytes(count: 4))
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self.offset = pointerData.uint64FromAlignedBytes(count: 4)
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self.fileName = String(data: Data(bytes: pointerData.alignedBytes(count: fileNameLength)),
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encoding: .utf8)
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let extraFieldStart = pointerData.index
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while pointerData.index - extraFieldStart < extraFieldLength {
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// There are a lot of possible extra fields.
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// But we are (currently) only interested in Zip64 related fields (with headerID = 0x0001),
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// because they directly impact further extraction process.
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let headerID = pointerData.intFromAlignedBytes(count: 2)
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let size = pointerData.intFromAlignedBytes(count: 2)
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switch headerID {
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case 0x0001:
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if self.uncompSize == 0xFFFFFFFF {
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self.uncompSize = pointerData.uint64FromAlignedBytes(count: 8)
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}
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if self.compSize == 0xFFFFFFFF {
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self.compSize = pointerData.uint64FromAlignedBytes(count: 8)
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}
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if self.offset == 0xFFFFFFFF {
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self.offset = pointerData.uint64FromAlignedBytes(count: 8)
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}
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if self.diskNumberStart == 0xFFFF {
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self.diskNumberStart = pointerData.uint64FromAlignedBytes(count: 4)
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}
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default:
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pointerData.index += size
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}
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}
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self.fileComment = String(data: Data(bytes: pointerData.alignedBytes(count: fileCommentLength)),
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encoding: .utf8)
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// Let's check entry's values for consistency.
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guard self.versionNeeded <= 45
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else { throw ZipError.WrongVersion }
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guard self.diskNumberStart == currentDiskNumber
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else { throw ZipError.MultiVolumesNotSupported }
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guard self.generalPurposeBitFlags & 0x2000 == 0 ||
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self.generalPurposeBitFlags & 0x40 == 0 ||
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self.generalPurposeBitFlags & 0x01 == 0
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else { throw ZipError.EncryptionNotSupported }
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guard self.generalPurposeBitFlags & 0x20 == 0
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else { throw ZipError.PatchingNotSupported }
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guard self.compressionMethod == 8 || self.compressionMethod == 0
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else { throw ZipError.CompressionNotSupported }
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}
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}
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struct EndOfCentralDirectory {
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private(set) var currentDiskNumber: UInt64
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private(set) var cdDiskNumber: UInt64
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private(set) var cdEntries: UInt64
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private(set) var cdSize: UInt64
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private(set) var cdOffset: UInt64
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init(_ pointerData: inout DataWithPointer) throws {
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/// Indicates if Zip64 records should be present.
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var zip64RecordExists = false
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/// Number of current disk.
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self.currentDiskNumber = pointerData.uint64FromAlignedBytes(count: 2)
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/// Number of the disk with the start of CD.
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self.cdDiskNumber = pointerData.uint64FromAlignedBytes(count: 2)
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guard self.currentDiskNumber == self.cdDiskNumber
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else { throw ZipError.MultiVolumesNotSupported }
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/// Number of CD entries on the current disk.
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var cdEntriesCurrentDisk = pointerData.uint64FromAlignedBytes(count: 2)
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/// Total number of CD entries.
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self.cdEntries = pointerData.uint64FromAlignedBytes(count: 2)
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guard cdEntries == cdEntriesCurrentDisk
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else { throw ZipError.MultiVolumesNotSupported }
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/// Size of Central Directory.
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self.cdSize = pointerData.uint64FromAlignedBytes(count: 4)
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/// Offset to the start of Central Directory.
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self.cdOffset = pointerData.uint64FromAlignedBytes(count: 4)
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let zipCommentLength = pointerData.intFromAlignedBytes(count: 2)
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// Check if zip64 records are present.
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if self.currentDiskNumber == 0xFFFF || self.cdDiskNumber == 0xFFFF ||
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cdEntriesCurrentDisk == 0xFFFF || self.cdEntries == 0xFFFF ||
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self.cdSize == 0xFFFFFFFF || self.cdOffset == 0xFFFFFFFF {
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zip64RecordExists = true
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}
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// There is also a .ZIP file comment, but we don't need it.
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// Here's how it can be processed:
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// let zipComment = String(data: Data(bytes: pointerData.alignedBytes(count: zipCommentLength)),
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// encoding: .utf8)
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if zip64RecordExists { // We need to find Zip64 end of CD locator.
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// Back to start of end of CD record.
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pointerData.index -= zipCommentLength + 22
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// Zip64 locator takes exactly 20 bytes.
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pointerData.index -= 20
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// Check signature.
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guard pointerData.uint64FromAlignedBytes(count: 4) == 0x07064b50
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else { throw ZipError.WrongSignature }
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let zip64CDStartDisk = pointerData.uint64FromAlignedBytes(count: 4)
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guard self.currentDiskNumber == zip64CDStartDisk
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else { throw ZipError.MultiVolumesNotSupported }
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let zip64CDEndOffset = pointerData.uint64FromAlignedBytes(count: 8)
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let totalDisks = pointerData.uint64FromAlignedBytes(count: 1)
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guard totalDisks == 1
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else { throw ZipError.MultiVolumesNotSupported }
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// Now we need to move to Zip64 End of CD.
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pointerData.index = Int(UInt(truncatingBitPattern: zip64CDEndOffset))
|
|
|
|
// Check signature.
|
|
guard pointerData.uint64FromAlignedBytes(count: 4) == 0x06064b50
|
|
else { throw ZipError.WrongSignature }
|
|
|
|
// Following 8 bytes are size of end of zip64 CD, but we don't need it.
|
|
_ = pointerData.uint64FromAlignedBytes(count: 8)
|
|
|
|
// Next two bytes are version of compressor, but we don't need it.
|
|
_ = pointerData.uint64FromAlignedBytes(count: 2)
|
|
let versionNeeded = pointerData.uint64FromAlignedBytes(count: 2)
|
|
guard versionNeeded <= 45
|
|
else { throw ZipError.WrongVersion }
|
|
|
|
// Update values read from basic End of CD with the ones from Zip64 End of CD.
|
|
self.currentDiskNumber = pointerData.uint64FromAlignedBytes(count: 4)
|
|
self.cdDiskNumber = pointerData.uint64FromAlignedBytes(count: 4)
|
|
guard currentDiskNumber == cdDiskNumber
|
|
else { throw ZipError.MultiVolumesNotSupported }
|
|
|
|
cdEntriesCurrentDisk = pointerData.uint64FromAlignedBytes(count: 8)
|
|
self.cdEntries = pointerData.uint64FromAlignedBytes(count: 8)
|
|
guard cdEntries == cdEntriesCurrentDisk
|
|
else { throw ZipError.MultiVolumesNotSupported }
|
|
|
|
self.cdSize = pointerData.uint64FromAlignedBytes(count: 8)
|
|
self.cdOffset = pointerData.uint64FromAlignedBytes(count: 8)
|
|
|
|
// Then, there might be 'zip64 extensible data sector' with 'special purpose data'.
|
|
// But we don't need them currently, so let's skip them.
|
|
|
|
// To find the size of these data:
|
|
// let specialPurposeDataSize = zip64EndCDSize - 56
|
|
}
|
|
}
|
|
|
|
}
|