/// <summary>
/// zip文件头的实例化
/// </summary>
/// <param name="file">资料实体</param>
/// <returns></returns>
private E_LocalFileHeader FileHeaderInstance(E_SourceFile file)
{
E_LocalFileHeader l = new E_LocalFileHeader();
l.MinExtractVersion = BitConverter.GetBytes((short)0x000a);
l.PurposeFlag = BitConverter.GetBytes((short)0x0800);
//压缩方法使用默认
//文件最后修改时间和日期不用管
l.CRC32 = file.CRC32;
l.CmpSize = BitConverter.GetBytes((int)file.FileSize);
l.UnCmpSize = BitConverter.GetBytes((int)file.FileSize);
l.FileNameLength = BitConverter.GetBytes((short)Encoding.UTF8.GetBytes(file.FileName).Length);
//文件扩展区长度默认为0即可
l.FileName = Encoding.UTF8.GetBytes(file.FileName);
//数据区填充null
l.ExtraField = null;
return(l);
}
/// <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);
}
