C#.net识别zip文件

Question

我目前正在使用SharpZip api处理我的zip文件条目.它适用于压缩和解压缩.但是,我无法确定文件是否为zip文件.我需要知道是否有办法检测文件流是否可以解压缩.原来我用过

FileStream lFileStreamIn = File.OpenRead(mSourceFile);
lZipFile = new ZipFile(lFileStreamIn);
ZipInputStream lZipStreamTester = new ZipInputStream(lFileStreamIn, mBufferSize);// not working
lZipStreamTester.Read(lBuffer, 0, 0);
if (lZipStreamTester.CanDecompressEntry)
{

LZipStreamTester每次都变为null,if语句失败.我尝试使用/不使用缓冲区.任何人都可以提供任何有关原因的见解吗？我知道我可以检查文件扩展名.我需要的东西比那更明确.我也知道zip有一个神奇的#(PK的东西),但它不能保证它永远存在,因为它不是格式的要求.

另外我读到.net 4.5有本机zip支持,所以我的项目可能会迁移到而不是sharpzip,但我仍然需要没有看到类似于CanDecompressEntry的方法/参数:http://msdn.microsoft.com/en-我们/库/ 3z72378a%28V = vs.110 29%

我的最后一招是使用try catch并尝试解压缩文件.

Answer 1

这是需要处理未压缩,PKZIP压缩(sharpziplib)或GZip压缩(内置.net)数据的组件的基类.也许比你需要的更多,但应该让你去.这是使用@ PhonicUK的建议来解析数据流的标头的示例.您在小工厂mathod中看到的派生类处理了PKZip和GZip解压缩的细节.

abstract class Expander
{
    private const int ZIP_LEAD_BYTES = 0x04034b50;
    private const ushort GZIP_LEAD_BYTES = 0x8b1f;

    public abstract MemoryStream Expand(Stream stream); 

    internal static bool IsPkZipCompressedData(byte[] data)
    {
        Debug.Assert(data != null && data.Length >= 4);
        // if the first 4 bytes of the array are the ZIP signature then it is compressed data
        return (BitConverter.ToInt32(data, 0) == ZIP_LEAD_BYTES);
    }

    internal static bool IsGZipCompressedData(byte[] data)
    {
        Debug.Assert(data != null && data.Length >= 2);
        // if the first 2 bytes of the array are theG ZIP signature then it is compressed data;
        return (BitConverter.ToUInt16(data, 0) == GZIP_LEAD_BYTES);
    }

    public static bool IsCompressedData(byte[] data)
    {
        return IsPkZipCompressedData(data) || IsGZipCompressedData(data);
    }

    public static Expander GetExpander(Stream stream)
    {
        Debug.Assert(stream != null);
        Debug.Assert(stream.CanSeek);
        stream.Seek(0, 0);

        try
        {
            byte[] bytes = new byte[4];

            stream.Read(bytes, 0, 4);

            if (IsGZipCompressedData(bytes))
                return new GZipExpander();

            if (IsPkZipCompressedData(bytes))
                return new ZipExpander();

            return new NullExpander();
        }
        finally
        {
            stream.Seek(0, 0);  // set the stream back to the begining
        }
    }
}

Answer 2

查看/sf/answers/1161099411/参考

检查以下链接:

icsharpcode-sharpziplib - 验证 - 压缩文件

如何对检查-IF-A-文件被压缩,在C#

ZIP文件始终以0x04034b50(4字节)开头
查看更多:http://en.wikipedia.org/wiki/Zip_(file_format)#File_headers

样品用法:

        bool isPKZip = IOHelper.CheckSignature(pkg, 4, IOHelper.SignatureZip);
        Assert.IsTrue(isPKZip, "Not ZIP the package : " + pkg);

// http://blog.somecreativity.com/2008/04/08/how-to-check-if-a-file-is-compressed-in-c/
    public static partial class IOHelper
    {
        public const string SignatureGzip = "1F-8B-08";
        public const string SignatureZip = "50-4B-03-04";

        public static bool CheckSignature(string filepath, int signatureSize, string expectedSignature)
        {
            if (String.IsNullOrEmpty(filepath)) throw new ArgumentException("Must specify a filepath");
            if (String.IsNullOrEmpty(expectedSignature)) throw new ArgumentException("Must specify a value for the expected file signature");
            using (FileStream fs = new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                if (fs.Length < signatureSize)
                    return false;
                byte[] signature = new byte[signatureSize];
                int bytesRequired = signatureSize;
                int index = 0;
                while (bytesRequired > 0)
                {
                    int bytesRead = fs.Read(signature, index, bytesRequired);
                    bytesRequired -= bytesRead;
                    index += bytesRead;
                }
                string actualSignature = BitConverter.ToString(signature);
                if (actualSignature == expectedSignature) return true;
                return false;
            }
        }

    }

Answer 3

你可以:

• 使用try-catch结构并尝试读取潜在zip文件的结构
• 解析文件头以查看它是否是zip文件

ZIP文件总是以0x04034b50作为前4个字节开始(http://en.wikipedia.org/wiki/Zip_(file_format)#File_headers)