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Better performance in RemoveEntries #63

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Better performance in RemoveEntries #63

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Refactor RemoveEntries 
- Instead of decompressing and recompressing the data, it is simply copied into the new zip file.
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@thomas694
thomas694 committed Jan 20, 2025
commit 7de3f8837fcf1789d78f01eb5ccfe796d98494e4
111 changes: 79 additions & 32 deletions src/ZipStorer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,31 +29,31 @@ public enum Compression : ushort
public class ZipFileEntry
{
/// <summary>Compression method</summary>
public Compression Method {get; set;}
public Compression Method { get; set; }
/// <summary>Full path and filename as stored in Zip</summary>
public string FilenameInZip {get; set;}
public string FilenameInZip { get; set; }
/// <summary>Original file size</summary>
public long FileSize {get; set;}
public long FileSize { get; set; }
/// <summary>Compressed file size</summary>
public long CompressedSize {get; set;}
public long CompressedSize { get; set; }
/// <summary>Offset of header information inside Zip storage</summary>
public long HeaderOffset {get; set;}
public long HeaderOffset { get; set; }
/// <summary>Offset of file inside Zip storage</summary>
public long FileOffset {get; set;}
public long FileOffset { get; set; }
/// <summary>Size of header information</summary>
public uint HeaderSize {get; set;}
public uint HeaderSize { get; set; }
/// <summary>32-bit checksum of entire file</summary>
public uint Crc32 {get; set;}
public uint Crc32 { get; set; }
/// <summary>Last modification time of file</summary>
public DateTime ModifyTime {get; set;}
public DateTime ModifyTime { get; set; }
/// <summary>Creation time of file</summary>
public DateTime CreationTime {get; set;}
public DateTime CreationTime { get; set; }
/// <summary>Last access time of file</summary>
public DateTime AccessTime {get; set;}
public DateTime AccessTime { get; set; }
/// <summary>User comment for file</summary>
public string Comment {get; set;}
public string Comment { get; set; }
/// <summary>True if UTF8 encoding for filename and comments, false if default (CP 437)</summary>
public bool EncodeUTF8 {get; set;}
public bool EncodeUTF8 { get; set; }

/// <summary>Overriden method</summary>
/// <returns>Filename in Zip</returns>
Expand All @@ -65,14 +65,16 @@ public override string ToString()

#region Public properties
/// <summary>True if UTF8 encoding for filename and comments, false if default (CP 437)</summary>
public bool EncodeUTF8 {get; set;} = false;
public bool EncodeUTF8 { get; set; } = false;
/// <summary>Force deflate algotithm even if it inflates the stored file. Off by default.</summary>
public bool ForceDeflating {get; set;} = false;
#endregion
public bool ForceDeflating { get; set; } = false;
#endregion

#region Private fields
#region Private fields
// List of files to store
private List<ZipFileEntry> Files = new List<ZipFileEntry>();
private readonly List<ZipFileEntry> Files = new List<ZipFileEntry>();
// List of files in Central Directory
private readonly List<ZipFileEntry> CentralDirectoryFiles = new List<ZipFileEntry>();
// Filename of storage file
private string FileName;
// Stream object of storage file
Expand Down Expand Up @@ -212,7 +214,10 @@ public static ZipStorer Open(Stream stream, FileAccess access, bool leaveOpen =
};

if (zip.ReadFileInfo())
{
zip.ReadCentralDir();
return zip;
}

if (!leaveOpen)
zip.Close();
Expand Down Expand Up @@ -375,7 +380,7 @@ public List<ZipFileEntry> ReadCentralDir()
if (this.CentralDirImage == null)
throw new InvalidOperationException("Central directory currently does not exist");

List<ZipFileEntry> result = new List<ZipFileEntry>();
CentralDirectoryFiles.Clear();

for (int pointer = 0; pointer < this.CentralDirImage.Length;)
{
Expand All @@ -396,11 +401,14 @@ public List<ZipFileEntry> ReadCentralDir()
uint headerSize = (uint)(46 + filenameSize + extraSize + commentSize);
DateTime modifyTimeDT = DosTimeToDateTime(modifyTime) ?? DateTime.Now;

EncodeUTF8 |= encodeUTF8;
Encoding encoder = encodeUTF8 ? Encoding.UTF8 : DefaultEncoding;

ZipFileEntry zfe = new ZipFileEntry()
{
Method = (Compression)method,
EncodeUTF8 = encodeUTF8,
Comment = string.Empty,
FilenameInZip = encoder.GetString(CentralDirImage, pointer + 46, filenameSize),
FileOffset = headerOffset == 0xFFFFFFFF ? 0 : GetFileOffset(headerOffset),
FileSize = fileSize,
Expand All @@ -422,11 +430,11 @@ public List<ZipFileEntry> ReadCentralDir()
if (headerOffset == 0xFFFFFFFF) zfe.FileOffset = GetFileOffset(zfe.HeaderOffset);
}

result.Add(zfe);
CentralDirectoryFiles.Add(zfe);
pointer += 46 + filenameSize + extraSize + commentSize;
}

return result;
return CentralDirectoryFiles;
}

/// <summary>
Expand Down Expand Up @@ -561,24 +569,65 @@ public static bool RemoveEntries(ref ZipStorer zip, List<ZipFileEntry> zfes)
if (!(zip.ZipFileStream is FileStream))
throw new InvalidOperationException("RemoveEntries is allowed just over streams of type FileStream");

//Get full list of entries
var fullList = zip.ReadCentralDir();
// Just remove affected entries from the newly added files list
zip.Files.RemoveAll(x => zfes.Contains(x));

//In order to delete we need to create a copy of the zip file excluding the selected items
var tempZipName = Path.GetTempFileName();
var tempEntryName = Path.GetTempFileName();
// In order to delete we need to create a copy of the zip file excluding the selected items
var tempZipName = zip.FileName + ".tmp";

try
{
var tempZip = ZipStorer.Create(tempZipName, string.Empty);

foreach (ZipFileEntry zfe in fullList)
var br = new BinaryReader(zip.ZipFileStream);
long offset = 0;

for (int listIndex = 0; listIndex <= 1; listIndex++)
{
if (!zfes.Contains(zfe))
var list = listIndex == 0 ? zip.CentralDirectoryFiles : zip.Files;

for (int index = 0; index < list.Count; index++)
{
if (zip.ExtractFile(zfe, tempEntryName))
var zfe = list[index];
if (!zfes.Contains(zfe))
{
// copy to new zip

// Copy local header and consider filename and extra field lengths
zip.ZipFileStream.Position = zfe.HeaderOffset;
var bytes = br.ReadBytes(26);
tempZip.ZipFileStream.Write(bytes, 0, bytes.Length);
var filenameLength = br.ReadInt16();
var extraFieldLength = br.ReadInt16();
tempZip.ZipFileStream.Write(BitConverter.GetBytes((ushort)filenameLength), 0, 2);
tempZip.ZipFileStream.Write(BitConverter.GetBytes((ushort)extraFieldLength), 0, 2);
bytes = br.ReadBytes(filenameLength + extraFieldLength);
tempZip.ZipFileStream.Write(bytes, 0, bytes.Length);

// Buffered copy
byte[] buffer = new byte[65535];
long bytesPending = zfe.CompressedSize;
while (bytesPending > 0)
{
int bytesRead = zip.ZipFileStream.Read(buffer, 0, (int)Math.Min(bytesPending, buffer.Length));
tempZip.ZipFileStream.Write(buffer, 0, bytesRead);

bytesPending -= bytesRead;
}
tempZip.ZipFileStream.Flush();

// Adjust offsets
if (zfe.FileOffset == 0) zfe.FileOffset = zip.GetFileOffset(zfe.HeaderOffset);
zfe.HeaderOffset += offset;
zfe.FileOffset += offset;

// Add to new files list
tempZip.Files.Add(zfe);
}
else
{
tempZip.AddFile(zfe.Method, tempEntryName, zfe.FilenameInZip, zfe.Comment);
// offset correction
offset -= zfe.HeaderSize + zfe.CompressedSize;
}
}
}
Expand All @@ -599,8 +648,6 @@ public static bool RemoveEntries(ref ZipStorer zip, List<ZipFileEntry> zfes)
{
if (File.Exists(tempZipName))
File.Delete(tempZipName);
if (File.Exists(tempEntryName))
File.Delete(tempEntryName);
}
return true;
}
Expand Down