我使用了https://en.wikipedia.org/wiki/List_of_file_signatures，只是为我的 zip 文件添加了一个额外的字节，以区分我的 zip 文件和 Word 文档（它们共享前四个字节）。
这是我的代码：
public class ZipFileUtilities
{
private static readonly byte[] ZipBytes1 = { 0x50, 0x4b, 0x03, 0x04, 0x0a };
private static readonly byte[] GzipBytes = { 0x1f, 0x8b };
private static readonly byte[] TarBytes = { 0x1f, 0x9d };
private static readonly byte[] LzhBytes = { 0x1f, 0xa0 };
private static readonly byte[] Bzip2Bytes = { 0x42, 0x5a, 0x68 };
private static readonly byte[] LzipBytes = { 0x4c, 0x5a, 0x49, 0x50 };
private static readonly byte[] ZipBytes2 = { 0x50, 0x4b, 0x05, 0x06 };
private static readonly byte[] ZipBytes3 = { 0x50, 0x4b, 0x07, 0x08 };
public static byte[] GetFirstBytes(string filepath, int length)
{
using (var sr = new StreamReader(filepath))
{
sr.BaseStream.Seek(0, 0);
var bytes = new byte[length];
sr.BaseStream.Read(bytes, 0, length);
return bytes;
}
}
public static bool IsZipFile(string filepath)
{
return IsCompressedData(GetFirstBytes(filepath, 5));
}
public static bool IsCompressedData(byte[] data)
{
foreach (var headerBytes in new[] { ZipBytes1, ZipBytes2, ZipBytes3, GzipBytes, TarBytes, LzhBytes, Bzip2Bytes, LzipBytes })
{
if (HeaderBytesMatch(headerBytes, data))
return true;
}
return false;
}
private static bool HeaderBytesMatch(byte[] headerBytes, byte[] dataBytes)
{
if (dataBytes.Length < headerBytes.Length)
throw new ArgumentOutOfRangeException(nameof(dataBytes),
$"Passed databytes length ({dataBytes.Length}) is shorter than the headerbytes ({headerBytes.Length})");
for (var i = 0; i < headerBytes.Length; i++)
{
if (headerBytes[i] == dataBytes[i]) continue;
return false;
}
return true;
}
}
可能有更好的编码方法，特别是字节比较，但由于它是一个可变长度的字节比较（取决于被检查的签名），我觉得至少这段代码是可读的——至少对我来说是这样。