解压缩后的 GZipStream 长度

引言

如文档所述，GZipStream 的 Length 属性不受支持。因此，你无法真正知道你即将提取的文件的大小。

使用代码

/// <summary>
/// Extracts the original filesize of the compressed file.
/// </summary>
/// <param name="fi">GZip file to handle</param>
/// <returns>Size of the compressed file, when its decompressed.</returns>
/// <remarks>More information at http://tools.ietf.org/html/rfc1952 section 2.3</remarks>
public static int GetGzOriginalFileSize(string fi)
{
    return GetGzOriginalFileSize(new FileInfo(fi));
}
/// <summary>
/// Extracts the original filesize of the compressed file.
/// </summary>
/// <param name="fi">GZip file to handle</param>
/// <returns>Size of the compressed file, when its decompressed.</returns>
/// <remarks>More information at http://tools.ietf.org/html/rfc1952 section 2.3</remarks>
public static int GetGzOriginalFileSize(FileInfo fi)
{
    try
    {
        using (FileStream fs = fi.OpenRead())
        {
            try
            {
                byte[] fh = new byte[3];
                fs.Read(fh, 0, 3);
                if (fh[0] == 31 && fh[1] == 139 && fh[2] == 8) //If magic numbers are 31 and 139 and the deflation id is 8 then...
                {
                    byte[] ba = new byte[4];
                    fs.Seek(-4, SeekOrigin.End);
                    fs.Read(ba, 0, 4);
                    return BitConverter.ToInt32(ba, 0);
                }
                else
                    return -1;
            }
            finally
            {
                fs.Close();
            }
        }
    }
    catch (Exception)
    {
        return -1;
    }
}

很简单，你只需调用 GetGzOriginalFileSize 方法并解析文件路径或 FileInfo 对象，即可获得解压缩后的文件大小。

资源

  C# 和我

历史

  2013-08-16：首次发布。