GZip Decompression Gives Blank File

Question

Given the code below, why is the decompression not working? "NewFile2.txt" should have the original, decompressed text, but the file is just blank.

ioTests.CompressFile(@"c:\newfile.txt", @"c:\newfile.txt.gz");
ioTests.DecompressFile(@"c:\newfile.txt.gz", @"c:\newfile2.txt");

public void CompressFile(string inFileName, string outFileName)
{
    FileStream inFile = new FileStream(inFileName, FileMode.Open);
    FileStream outFile = new FileStream(outFileName, FileMode.Create);

    GZipStream compStream = new GZipStream(outFile, CompressionMode.Compress);

    int theByte = inFile.ReadByte();

    while (theByte != -1)
    {
        compStream.WriteByte((byte)theByte);
        theByte = inFile.ReadByte();
    }

    compStream.Close();
}

public void DecompressFile(string inFileName, string outFileName)
{
    FileStream inFile = new FileStream(inFileName, FileMode.Open);
    FileStream outFile = new FileStream(outFileName, FileMode.CreateNew);

    GZipStream compStream = new GZipStream(inFile, CompressionMode.Decompress);

    int theByte = compStream.ReadByte();

    while (theByte != -1)
    {
        outFile.WriteByte((byte)theByte);

        theByte = compStream.ReadByte();
    }

    compStream.Close();
}

Shouldn't you be writing decompressed file to the "outFile" ? — Sedat Kapanoglu, Jun 15 '11 at 07:17
@ssg: Yeah that's what I'm doing (I think). The outfile is the one `WriteByte`ing from the (now) uncompressed compstream byte (held in `theByte`. — richard, Jun 15 '11 at 07:21

score 4 · Accepted Answer · answered Jun 15 '11 at 07:21

4

outFile.Flush(); // after your loop

answered Jun 15 '11 at 07:21

Waleed

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You're my favorite dude tonight! Thanks! That worked! (I'm such an idiot for not seeing that. I was going cross-eyed) – richard Jun 15 '11 at 07:23
@Richard : LoL, we all do such kind of crap when doing night coding :P – Waleed Jun 15 '11 at 07:24

score 2 · Answer 2 · answered Jun 15 '11 at 07:33

2

I prefer

outFile.Close()

as that flushes the stream and calls the Dispose method, releasing allocated resources.

answered Jun 15 '11 at 07:33

Skizz

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That is actually what I did instead. But Waleed was right that the stream wasn't flushing. – richard Jun 15 '11 at 07:37

score 2 · Answer 3 · answered Jun 15 '11 at 07:40

Since the streams you use implement the IDisposable interface, you should Dispose() / Close() your classes, or use the using statement to do this automatically:

    using (FileStream inFile = new FileStream(inFileName, FileMode.Open))
    using (FileStream outFile = new FileStream(outFileName, FileMode.Create))

    using (GZipStream compStream = new GZipStream(outFile, CompressionMode.Compress)) {

        int theByte = inFile.ReadByte();
        // ... Rest of your code

    }

This roughly translates to:

    try {
       FileStream inFile = new FileStream(inFileName, FileMode.Open);
       FileStream outFile = new FileStream(outFileName, FileMode.Create);
       GZipStream compStream = new GZipStream(outFile, CompressionMode.Compress);

        int theByte = inFile.ReadByte();
        // ... Rest of your code

    } finally {
        if (inFile != null) inFile.Dispose();
        if (outFile != null) outFile.Dispose();
        if (compStream != null) compStream.Dispose();
    }

GZip Decompression Gives Blank File

3 Answers3