CODEWITHSUNDEEP
c#.netcompressiongzip
MoshMosh
MoshMosh

Reputation: 71

uncompressed file is bigger than original file in GZIP

i'm using the following function to compress(thanks to http://www.dotnetperls.com/):

public static void CompressStringToFile(string fileName, string value)
    {
        // A.
        // Write string to temporary file.
        string temp = Path.GetTempFileName();
        File.WriteAllText(temp, value);

        // B.
        // Read file into byte array buffer.
        byte[] b;
        using (FileStream f = new FileStream(temp, FileMode.Open))
        {
            b = new byte[f.Length];
            f.Read(b, 0, (int)f.Length);
        }

        // C.
        // Use GZipStream to write compressed bytes to target file.
        using (FileStream f2 = new FileStream(fileName, FileMode.Create))
        using (GZipStream gz = new GZipStream(f2, CompressionMode.Compress, false))
        {
            gz.Write(b, 0, b.Length);
        }
    }

and for decompress:

static byte[] Decompress(byte[] gzip)
    {
        // Create a GZIP stream with decompression mode.
        // ... Then create a buffer and write into while reading from the GZIP stream.
        using (GZipStream stream = new GZipStream(new MemoryStream(gzip), CompressionMode.Decompress))
        {
            const int size = 4096;
            byte[] buffer = new byte[size];
            using (MemoryStream memory = new MemoryStream())
            {
                int count = 0;
                do
                {
                    count = stream.Read(buffer, 0, size);
                    if (count > 0)
                    {
                        memory.Write(buffer, 0, count);
                    }
                }
                while (count > 0);
                return memory.ToArray();
            }
        }
    }

so my goal is actually compress log files and than to decompress them in memory and compare the uncompressed file to the original file in order to check that the compression succeeded and i'm able to open the compressed file successfuly. the problem is that the uncompressed file is most of the time bigger than the original file and my compare check is failing altough the compression probably succeeded.

any idea why ?

btw here how i compare the uncompressed file to the original file:

static bool FileEquals(byte[] file1, byte[] file2)
    {
        if (file1.Length == file2.Length)
        {
            for (int i = 0; i < file1.Length; i++)
            {
                if (file1[i] != file2[i])
                {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

Upvotes: 0

Views: 1042

Answers (2)

nedruod
nedruod

Reputation: 1122

Think you'd be better off with the simplest API call, try Stream.CopyTo(). I can't find the error in your code. If I was working on it, I'd probably make sure everything is getting flushed properly.. can't recall if GZipStream is going to flush its output to FileStream when the using block closes.. but then you are also saying that the final file is larger, not smaller.

Anyhow, best policy in my experience.. don't rewrite gotcha prone code when you don't need to. At least you tested it ;)

Upvotes: 1

Slashy
Slashy

Reputation: 1881

Try this method to compress a file:

public static byte[] Compress(byte[] raw)
{
using (MemoryStream memory = new MemoryStream())
{
    using (GZipStream gzip = new GZipStream(memory,
    CompressionMode.Compress, true))
    {
    gzip.Write(raw, 0, raw.Length);
    }
    return memory.ToArray();
   }
  }
}

And this to decompress :

 static byte[] Decompress(byte[] gzip)
{
// Create a GZIP stream with decompression mode.
// ... Then create a buffer and write into while reading from the GZIP stream.
using (GZipStream stream = new GZipStream(new MemoryStream(gzip), CompressionMode.Decompress))
{
    const int size = 4096;
    byte[] buffer = new byte[size];
    using (MemoryStream memory = new MemoryStream())
    {
    int count = 0;
    do
    {
        count = stream.Read(buffer, 0, size);
        if (count > 0)
        {
        memory.Write(buffer, 0, count);
        }
    }
    while (count > 0);
    return memory.ToArray();
    }
}
}

}

Tell me if it worked.

Goodluck.

Upvotes: 1

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