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[7-Zip] Some code and comments improvements to open and info functions

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Timofey Solomko
2018-03-17 15:34:12 +03:00
parent 42fdac0a79
commit 2e3867afde
1 changed files with 32 additions and 45 deletions
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Sources/7-Zip/7zContainer.swift
+32 -45
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@@ -27,10 +27,8 @@ public class SevenZipContainer: Container {
*/
public static func open(container data: Data) throws -> [SevenZipEntry] {
var entries = [SevenZipEntry]()
guard let header = try readHeader(data)
else { return [] }
guard let files = header.fileInfo?.files
guard let header = try readHeader(data),
let files = header.fileInfo?.files
else { return [] }
/// Total count of non-empty files. Used to iterate over SubstreamInfo.
@@ -40,7 +38,7 @@ public class SevenZipContainer: Container {
var folderIndex = 0
/// Index of currently extracted file in `headerInfo.fileInfo.files`.
var fileInFolderCount = 0
var folderFileIndex = 0
/// Index of currently read stream.
var streamIndex = -1
@@ -52,21 +50,18 @@ public class SevenZipContainer: Container {
var folderCRC = CheckSums.crc32(Data())
/// `ByteReader` object with unpacked stream's data.
var rawFileData = ByteReader(data: Data())
var unpackedStreamData = ByteReader(data: Data())
let byteReader = ByteReader(data: data)
for fileIndex in 0..<files.count {
let file = files[fileIndex]
for file in files {
let info: SevenZipEntryInfo
let data: Data?
if !file.isEmptyStream {
// Without `SevenZipStreamInfo` and `SevenZipPackInfo` objects,
// we cannot find file data location in container.
guard let streamInfo = header.mainStreams
else { throw SevenZipError.internalStructureError }
guard let packInfo = streamInfo.packInfo
// Without `SevenZipStreamInfo` and `SevenZipPackInfo` we cannot find file data in container.
guard let streamInfo = header.mainStreams,
let packInfo = streamInfo.packInfo
else { throw SevenZipError.internalStructureError }
// SubstreamInfo is required to get files' data, and without it we can only return files' info.
@@ -79,20 +74,18 @@ public class SevenZipContainer: Container {
guard folderIndex < streamInfo.coderInfo.numFolders
else { throw SevenZipError.internalStructureError }
/// Folder, which contains current file.
/// Folder which contains current file.
let folder = streamInfo.coderInfo.folders[folderIndex]
// There may be several streams corresponding to a single folder,
// so we have to iterate over them, if necessary.
// There may be several streams in a single folder, so we have to iterate over them, if necessary.
// If we switched folders or completed reading of a stream we need to move to the next stream.
if fileInFolderCount == 0 || rawFileData.isFinished {
if folderFileIndex == 0 || unpackedStreamData.isFinished {
streamIndex += 1
// First, we move to the stream's offset.
// We don't have any guarantees that streams will be enountered in the same order,
// as they are placed in the container.
// Thus, we have to start moving to stream's offset from the beginning.
// (Or, maybe, this is incorrect and the order of streams is guaranteed).
// First, we move to the stream's offset. We don't have any guarantees that streams will be
// enountered in the same order, as they are placed in the container. Thus, we have to start moving
// to stream's offset from the beginning.
// TODO: Is this correct or the order of streams is guaranteed?
byteReader.offset = signatureHeaderSize + packInfo.packPosition // Pack offset.
if streamIndex != 0 {
for i in 0..<streamIndex {
@@ -110,26 +103,23 @@ public class SevenZipContainer: Container {
else { throw SevenZipError.wrongCRC }
}
// One stream can contain data of several files,
// so we need to decode the stream first, then split it into files.
rawFileData = ByteReader(data: try folder.unpack(data: streamData))
// One stream can contain data for several files, so we need to decode the stream first, then split
// it into files.
unpackedStreamData = ByteReader(data: try folder.unpack(data: streamData))
}
// `SevenZipSubstreamInfo` object must contain information about file's size
// and may also contain information about file's CRC32.
// `SevenZipSubstreamInfo` object must contain information about file's size and may also contain
// information about file's CRC32.
// File's unpack size is required to proceed.
// Next check ensures that we don't `unpackSizes` array's boundaries.
// File's unpacked size is required to proceed.
guard nonEmptyFileIndex < substreamInfo.unpackSizes.count
else { throw SevenZipError.internalStructureError }
let fileSize = substreamInfo.unpackSizes[nonEmptyFileIndex]
// Check, if we aren't about to read too much from a stream.
guard rawFileData.offset + fileSize <= rawFileData.size
guard unpackedStreamData.offset + fileSize <= unpackedStreamData.data.endIndex
else { throw SevenZipError.internalStructureError }
let fileData = Data(bytes: rawFileData.bytes(count: fileSize))
let fileData = Data(bytes: unpackedStreamData.bytes(count: fileSize))
let calculatedFileCRC = CheckSums.crc32(fileData)
if nonEmptyFileIndex < substreamInfo.digests.count {
@@ -144,23 +134,23 @@ public class SevenZipContainer: Container {
folderUnpackSize += fileSize
folderCRC = CheckSums.crc32(fileData, prevValue: folderCRC)
fileInFolderCount += 1
folderFileIndex += 1
nonEmptyFileIndex += 1
if fileInFolderCount >= folder.numUnpackSubstreams { // If we read all files in folder...
// We need to check folder's unpacked size as well as its CRC32 (if it is available).
if folderFileIndex >= folder.numUnpackSubstreams { // If we read all files in folder...
// Check folder's unpacked size as well as its CRC32 (if it is available).
guard folderUnpackSize == folder.unpackSize()
else { throw SevenZipError.wrongSize }
if let storedFolderCRC = folder.crc {
guard folderCRC == storedFolderCRC
else { throw SevenZipError.wrongCRC }
}
// Resetting folder's crc and unpack size.
// Reset folder's unpack size and CRC32.
folderCRC = CheckSums.crc32(Data())
folderUnpackSize = 0
// Resetting files count for the next folder.
fileInFolderCount = 0
// Moving to the next folder.
// Reset file index for the next folder.
folderFileIndex = 0
// Move to the next folder.
folderIndex += 1
}
} else {
@@ -191,10 +181,8 @@ public class SevenZipContainer: Container {
*/
public static func info(container data: Data) throws -> [SevenZipEntryInfo] {
var entries = [SevenZipEntryInfo]()
guard let header = try readHeader(data)
else { return [] }
guard let files = header.fileInfo?.files
guard let header = try readHeader(data),
let files = header.fileInfo?.files
else { return [] }
var nonEmptyFileIndex = 0
@@ -215,7 +203,6 @@ public class SevenZipContainer: Container {
}
private static func readHeader(_ data: Data) throws -> SevenZipHeader? {
/// Object with input data which supports convenient work with bit shifts.
let bitReader = MsbBitReader(data: data)
// **SignatureHeader**