ZipCentralDirectoryFileHeader.cs

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using System.Collections.Generic;
 
namespace System.IO.Compression;
 
internal struct ZipCentralDirectoryFileHeader
{
    public byte VersionMadeByCompatibility;
 
    public byte VersionMadeBySpecification;
 
    public ushort VersionNeededToExtract;
 
    public ushort GeneralPurposeBitFlag;
 
    public ushort CompressionMethod;
 
    public uint LastModified;
 
    public uint Crc32;
 
    public long CompressedSize;
 
    public long UncompressedSize;
 
    public ushort FilenameLength;
 
    public ushort ExtraFieldLength;
 
    public ushort FileCommentLength;
 
    public int DiskNumberStart;
 
    public ushort InternalFileAttributes;
 
    public uint ExternalFileAttributes;
 
    public long RelativeOffsetOfLocalHeader;
 
    public byte[] Filename;
 
    public byte[] FileComment;
 
    public List<ZipGenericExtraField> ExtraFields;
 
    public static bool TryReadBlock(BinaryReader reader, bool saveExtraFieldsAndComments, out ZipCentralDirectoryFileHeader header)
    {
        header = default(ZipCentralDirectoryFileHeader);
        if (reader.ReadUInt32() != 33639248)
        {
            return false;
        }
        header.VersionMadeBySpecification = reader.ReadByte();
        header.VersionMadeByCompatibility = reader.ReadByte();
        header.VersionNeededToExtract = reader.ReadUInt16();
        header.GeneralPurposeBitFlag = reader.ReadUInt16();
        header.CompressionMethod = reader.ReadUInt16();
        header.LastModified = reader.ReadUInt32();
        header.Crc32 = reader.ReadUInt32();
        uint num = reader.ReadUInt32();
        uint num2 = reader.ReadUInt32();
        header.FilenameLength = reader.ReadUInt16();
        header.ExtraFieldLength = reader.ReadUInt16();
        header.FileCommentLength = reader.ReadUInt16();
        ushort num3 = reader.ReadUInt16();
        header.InternalFileAttributes = reader.ReadUInt16();
        header.ExternalFileAttributes = reader.ReadUInt32();
        uint num4 = reader.ReadUInt32();
        header.Filename = reader.ReadBytes(header.FilenameLength);
        bool readUncompressedSize = num2 == uint.MaxValue;
        bool readCompressedSize = num == uint.MaxValue;
        bool readLocalHeaderOffset = num4 == uint.MaxValue;
        bool readStartDiskNumber = num3 == ushort.MaxValue;
        long position = reader.BaseStream.Position + header.ExtraFieldLength;
        Zip64ExtraField zip64ExtraField;
        using (Stream stream = new SubReadStream(reader.BaseStream, reader.BaseStream.Position, header.ExtraFieldLength))
        {
            if (saveExtraFieldsAndComments)
            {
                header.ExtraFields = ZipGenericExtraField.ParseExtraField(stream);
                zip64ExtraField = Zip64ExtraField.GetAndRemoveZip64Block(header.ExtraFields, readUncompressedSize, readCompressedSize, readLocalHeaderOffset, readStartDiskNumber);
            }
            else
            {
                header.ExtraFields = null;
                zip64ExtraField = Zip64ExtraField.GetJustZip64Block(stream, readUncompressedSize, readCompressedSize, readLocalHeaderOffset, readStartDiskNumber);
            }
        }
        reader.BaseStream.AdvanceToPosition(position);
        if (saveExtraFieldsAndComments)
        {
            header.FileComment = reader.ReadBytes(header.FileCommentLength);
        }
        else
        {
            reader.BaseStream.Position += header.FileCommentLength;
            header.FileComment = null;
        }
        header.UncompressedSize = ((!zip64ExtraField.UncompressedSize.HasValue) ? num2 : zip64ExtraField.UncompressedSize.Value);
        header.CompressedSize = ((!zip64ExtraField.CompressedSize.HasValue) ? num : zip64ExtraField.CompressedSize.Value);
        header.RelativeOffsetOfLocalHeader = ((!zip64ExtraField.LocalHeaderOffset.HasValue) ? num4 : zip64ExtraField.LocalHeaderOffset.Value);
        header.DiskNumberStart = ((!zip64ExtraField.StartDiskNumber.HasValue) ? num3 : zip64ExtraField.StartDiskNumber.Value);
        return true;
    }
}