mirror of
https://github.com/tsolomko/SWCompression.git
synced 2026-06-23 14:56:41 +00:00
Timofey Solomko
113 lines
4.4 KiB
Swift
113 lines
4.4 KiB
Swift
// Copyright (c) 2026 Timofey Solomko
|
|
// Licensed under MIT License
|
|
//
|
|
// See LICENSE for license information
|
|
|
|
import BitByteData
|
|
|
|
struct ZipEndOfCentralDirectory {
|
|
|
|
/// Number of the current disk.
|
|
private(set) var currentDiskNumber: UInt32
|
|
|
|
private(set) var cdEntries: UInt64
|
|
private(set) var cdOffset: UInt64
|
|
|
|
// There are two fields in the EndOfCD that aren't currently used anywhere except in the initalizer.
|
|
// /// Number of the disk with the start of CD.
|
|
// private var cdDiskNumber: UInt32
|
|
// private var cdSize: UInt64
|
|
|
|
init(_ byteReader: LittleEndianByteReader) throws {
|
|
/// Indicates if Zip64 records should be present.
|
|
var zip64RecordExists = false
|
|
|
|
self.currentDiskNumber = byteReader.uint32(fromBytes: 2)
|
|
var cdDiskNumber = byteReader.uint32(fromBytes: 2)
|
|
guard self.currentDiskNumber == cdDiskNumber
|
|
else { throw ZipError.multiVolumesNotSupported }
|
|
|
|
/// Number of CD entries on the current disk.
|
|
var cdEntriesCurrentDisk = byteReader.uint64(fromBytes: 2)
|
|
/// Total number of CD entries.
|
|
self.cdEntries = byteReader.uint64(fromBytes: 2)
|
|
guard cdEntries == cdEntriesCurrentDisk
|
|
else { throw ZipError.multiVolumesNotSupported }
|
|
|
|
/// Size of Central Directory.
|
|
var cdSize = byteReader.uint64(fromBytes: 4)
|
|
/// Offset to the start of Central Directory.
|
|
self.cdOffset = byteReader.uint64(fromBytes: 4)
|
|
|
|
// There is also a .ZIP file comment, but we don't need it.
|
|
// Here's how it can be processed:
|
|
// let zipCommentLength = byteReader.int(fromBytes: 2)
|
|
// let zipComment = String(data: Data(byteReader.bytes(count: zipCommentLength)),
|
|
// encoding: .utf8)
|
|
|
|
// Check if zip64 records are present.
|
|
if self.currentDiskNumber == 0xFFFF || cdDiskNumber == 0xFFFF ||
|
|
cdEntriesCurrentDisk == 0xFFFF || self.cdEntries == 0xFFFF ||
|
|
cdSize == 0xFFFFFFFF || self.cdOffset == 0xFFFFFFFF {
|
|
zip64RecordExists = true
|
|
}
|
|
|
|
if zip64RecordExists { // We need to find Zip64 end of CD locator.
|
|
// Back to start of end of CD record.
|
|
byteReader.offset -= 20
|
|
// Zip64 locator takes exactly 20 bytes.
|
|
byteReader.offset -= 20
|
|
|
|
// Check signature.
|
|
guard byteReader.uint32() == 0x07064b50
|
|
else { throw ZipError.wrongSignature }
|
|
|
|
let zip64CDStartDisk = byteReader.uint32()
|
|
guard self.currentDiskNumber == zip64CDStartDisk
|
|
else { throw ZipError.multiVolumesNotSupported }
|
|
|
|
let zip64CDEndOffset = byteReader.int(fromBytes: 8)
|
|
let totalDisks = byteReader.uint32()
|
|
guard totalDisks == 1
|
|
else { throw ZipError.multiVolumesNotSupported }
|
|
|
|
// Now we need to move to Zip64 End of CD.
|
|
byteReader.offset = zip64CDEndOffset
|
|
|
|
// Check signature.
|
|
guard byteReader.uint32() == 0x06064b50
|
|
else { throw ZipError.wrongSignature }
|
|
|
|
// Following 8 bytes are size of end of zip64 CD, but we don't need it.
|
|
_ = byteReader.uint64()
|
|
|
|
// Next two bytes are version of compressor, but we don't need it.
|
|
_ = byteReader.uint16()
|
|
let versionNeeded = byteReader.uint16()
|
|
guard versionNeeded & 0xFF <= 63
|
|
else { throw ZipError.wrongVersion }
|
|
|
|
// Update values read from basic End of CD with the ones from Zip64 End of CD.
|
|
self.currentDiskNumber = byteReader.uint32()
|
|
cdDiskNumber = byteReader.uint32()
|
|
guard currentDiskNumber == cdDiskNumber
|
|
else { throw ZipError.multiVolumesNotSupported }
|
|
|
|
cdEntriesCurrentDisk = byteReader.uint64()
|
|
self.cdEntries = byteReader.uint64()
|
|
guard cdEntries == cdEntriesCurrentDisk
|
|
else { throw ZipError.multiVolumesNotSupported }
|
|
|
|
cdSize = byteReader.uint64()
|
|
self.cdOffset = byteReader.uint64()
|
|
|
|
// 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
|
|
}
|
|
}
|
|
|
|
}
|