/// <summary>
/// zip中央目录的实例化
/// </summary>
/// <param name="file"></param>
/// <returns></returns>
private E_CentralDirFileHeader CentralDirInstance(E_SourceFile file)
{
E_CentralDirFileHeader c = new E_CentralDirFileHeader();
c.MadeVersion = BitConverter.GetBytes((short)0x003F);
c.MinExtractVersion = BitConverter.GetBytes((short)0x000a);
c.PurposeFlag = BitConverter.GetBytes((short)0x0800);
//压缩方法默认0,文件修改时间和日期默认0
c.CRC32 = file.CRC32;
c.CmpSize = BitConverter.GetBytes((int)file.FileSize);
c.UnCmpSize = BitConverter.GetBytes((int)file.FileSize);
c.FileNameLength = BitConverter.GetBytes((short)Encoding.UTF8.GetBytes(file.FileName).Length);
//扩展域长度,文件注释长度,开始位置的磁盘编号,为0即可
c.ExternalFileAttr = BitConverter.GetBytes(0x00000020);
//本地文件头的相对位移具体地方再做计算
c.FileName = Encoding.UTF8.GetBytes(file.FileName);
//扩展域和文件注释内容为null即可
return(c);
}
/// <summary>
/// 构建Zip结构
/// </summary>
/// <returns></returns>
private E_VirtualZipStruct BuildZipStruct()
{
E_VirtualZipStruct zipStruct = new E_VirtualZipStruct();
//定义头部和目录的集合(用于计算目录偏移量)
List <E_FileAndDir> fdList = new List <E_FileAndDir>();
//合计文件大小
long totalFileSize = 0;
//虚拟压缩包总大小(包含文件大小和头部,目录,尾部区域的字节)
long virtualZipSize = 0;
foreach (var file in fileList)
{
//1.构造头部区域
E_LocalFileHeader header = FileHeaderInstance(file);
zipStruct.Header.Add(new Tuple <byte[], string>(header.GetAllBytes(), file.PhyFilePath));
virtualZipSize += header.GetAllBytes().Count();
//2.构造目录部分
E_CentralDirFileHeader dir = CentralDirInstance(file);
//计算dir的偏移量
if (fdList.Count > 0)
{
dir.HeaderOffset = GetClassSize(fdList.Select(s => s.Header).ToList(), (int)totalFileSize);
}
zipStruct.Dir.AddRange(dir.GetAllBytes());
//向头部和目录集合添加记录
fdList.Add(new E_FileAndDir()
{
Header = header,
Dir = dir
});
totalFileSize += file.FileSize;
}
E_EndCentralDirRecord endDir = EndDirInstance(fdList, (int)totalFileSize);
zipStruct.End.AddRange(endDir.GetAllBytes());
virtualZipSize += zipStruct.Dir.Count();
virtualZipSize += zipStruct.End.Count();
virtualZipSize += totalFileSize;
zipStruct.ZipFileSize = (uint)virtualZipSize;
return(zipStruct);
}
