GZipStream complains that the magic number in the header is wrong
I am trying to use data from the National Weather Service (USA), but something changed recently and the GZip file no longer opens.
.NET 4.5 complains that ...
Message=The magic number in GZip header is not correct. Make sure you are passing in a GZip stream.
Source=System
StackTrace:
at System.IO.Compression.GZipDecoder.ReadHeader(InputBuffer input)
at System.IO.Compression.Inflater.Decode()
at System.IO.Compression.Inflater.Inflate(Byte[] bytes, Int32 offset, Int32 length)
at System.IO.Compression.DeflateStream.Read(Byte[] array, Int32 offset, Int32 count)
I don't understand what has changed, but it becomes a real show stopper. Can anyone with experience using GZip tell me what has changed to make this stop work?
File that works:
The file that doesn't work:
Update with sample code
const string url = "http://www.srh.noaa.gov/ridge2/Precip/qpehourlyshape/2015/201505/20150505/nws_precip_2015050505.tar.gz";
string appPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
string downloadPath = Path.Combine(appPath, Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), "nws_precip_2015050505.tar.gz");
using (var wc = new WebClient())
{
wc.DownloadFile(url, downloadPath);
}
string extractDirPath = Path.Combine(appPath, "Extracted");
if (!Directory.Exists(extractDirPath))
{
Directory.CreateDirectory(extractDirPath);
}
string extractFilePath = Path.Combine(extractDirPath, "nws_precip_2015050505.tar");
using (var fsIn = new FileStream(downloadPath, FileMode.Open, FileAccess.Read))
using (var fsOut = new FileStream(extractFilePath, FileMode.Create, FileAccess.Write))
using (var gz = new GZipStream(fsIn, CompressionMode.Decompress, true))
{
gz.CopyTo(fsOut);
}
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It looks like this SOMETIMES service is returning format files tar
disguised as .tar.gz
. This is very confusing, but if you check that the first two bytes are: 0x1F
and 0x8B
, you can determine if the file is a GZip by checking its magic numbers manually.
using (FileStream fs = new FileStream(downloadPath, FileMode.Open, FileAccess.Read))
{
byte[] buffer = new byte[2];
fs.Read(buffer, 0, buffer.Length);
if (buffer[0] == 0x1F
&& buffer[1] == 0x8B)
{
// It probably a GZip file
}
else
{
// It probably not a GZip file
}
}
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[Allowed] GZipStream complains that the magic number in the header is incorrect
// Exception magic number tar.gz file
Migcal error error
- The file doesn't compress in tar.gz correctly
- The file size is too large, over 1 + GB
Decision on it
-
use .net framework 4.5.1 for this exception // OR //
-
create exsiting app without changing .net framework. Follow the step for implementation.
-
Remane abc.tar.gz as abc (remove extension).
-
pass this file and direct name to compress function
-
* public static void Compress (DirectoryInfoSelected directory, string directoryPath)
{
foreach (FileInfo fileToCompress in directorySelected.GetFiles())
{
using (FileStream originalFileStream = fileToCompress.OpenRead())
{
if ((File.GetAttributes(fileToCompress.FullName) &
FileAttributes.Hidden) != FileAttributes.Hidden & fileToCompress.Extension != ".tar.gz")
{
using (FileStream compressedFileStream = File.Create(fileToCompress.FullName + ".tar.gz"))
{
using (System.IO.Compression.GZipStream compressionStream = new System.IO.Compression.GZipStream(compressedFileStream,
System.IO.Compression.CompressionMode.Compress))
{
originalFileStream.CopyTo(compressionStream);
}
}
FileInfo info = new FileInfo(directoryPath + "\\" + fileToCompress.Name + ".tar.gz");
}
}
}
}
3. implement this code in following exception handler try catch block
try
{
TarGzFilePath=@"c:\temp\abc.tar.gz";
FileStream streams = File.OpenRead(TarGzFilePath);
string FileName=string.Empty;
GZipInputStream tarGz = new GZipInputStream(streams);
TarInputStream tar = new TarInputStream(tarGz);
// exception will occured in below lines should apply try catch
TarEntry ze;
try
{
ze = tar.GetNextEntry();// exception occured here "magical number"
}
catch (Exception extra)
{
tar.Close();
tarGz.Close();
streams.Close();
//please close all above , other wise it will come with exception "tihs process use by another process"
//rename your file *for better accuracy you can copy file to other location
File.Move(@"c:\temp\abc.tar.gz", @"c:\temp\abc"); // rename file
DirectoryInfo directorySelected = new DirectoryInfo(Path.GetDirectoryName(@"c:\temp\abc"));
Compress(directorySelected, directoryPath); // directorySelected=c:\temp\abc , directoryPath=c:\temp\abc.tar.gz // process in step 2 function
streams = File.OpenRead(TarGzFilePath);
tarGz = new GZipInputStream(streams);
tar = new TarInputStream(tarGz);
ze = tar.GetNextEntry();
}
// do anything with extraction with your code
}
catch (exception ex)
{
tar.Close();
tarGz.Close();
streams.Close();
}
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