Question

My task is to decompress a packet(received) using zlib and then use an algoritm to make a picture from the data

The good news is that I have the code in C++,but the task is to do it in C#

C++

        //Read the first values of the packet received

        DWORD image[200 * 64] = {0}; //used for algoritm(width always = 200 and height always == 64)
        int imgIndex = 0; //used for algoritm
        unsigned char rawbytes_[131072] = {0}; //read below
        unsigned char * rawbytes = rawbytes_; //destrination parameter for decompression(ptr)
        compressed = r.Read<WORD>(); //the length of the compressed bytes(picture)
        uncompressed = r.Read<WORD>(); //the length that should be after decompression
        width = r.Read<WORD>(); //the width of the picture
        height = r.Read<WORD>(); //the height of the picture

        LPBYTE ptr = r.GetCurrentStream(); //the bytes(file that must be decompressed)

        outLen = uncompressed; //copy the len into another variable

        //Decompress

        if(uncompress((Bytef*)rawbytes, &outLen, ptr, compressed) != Z_OK)
        {
            printf("Could not uncompress the image code.\n");
            Disconnect();
            return;
        }

        //Algoritm to make up the picture
        // Loop through the data
        for(int c = 0; c < (int)height; ++c)
        {
            for(int r = 0; r < (int)width; ++r)
            {
                imgIndex = (height - 1 - c) * width + r;
                image[imgIndex] = 0xFF000000;
                if(-((1 << (0xFF & (r & 0x80000007))) & rawbytes[((c * width + r) >> 3)])) 
                    image[imgIndex] = 0xFFFFFFFF;
            }
        }

I’m trying to do this with zlib.NET ,but all demos have that code to decompress(C#)

    private void decompressFile(string inFile, string outFile)
    {
        System.IO.FileStream outFileStream = new System.IO.FileStream(outFile, System.IO.FileMode.Create);
        zlib.ZOutputStream outZStream = new zlib.ZOutputStream(outFileStream);
        System.IO.FileStream inFileStream = new System.IO.FileStream(inFile, System.IO.FileMode.Open);          
        try
        {
            CopyStream(inFileStream, outZStream);
        }
        finally
        {
            outZStream.Close();
            outFileStream.Close();
            inFileStream.Close();
        }
    }

    public static void CopyStream(System.IO.Stream input, System.IO.Stream output)
    {
        byte[] buffer = new byte[2000];
        int len;
        while ((len = input.Read(buffer, 0, 2000)) > 0)
        {
            output.Write(buffer, 0, len);
        }
        output.Flush();
    }

My problem:I don’t want to save the file after decompression,because I have to use the algoritm shown in the C++ code.

How to convert the byte[] array into a stream similiar to the one in the C# zlib code to decompress the data and then how to convert the stream back into byte array?

Also,How to change the zlib.NET code to NOT save files?

Answer 1

Just use MemoryStreams instead of FileStreams:

// Assuming inputData is a byte[]
MemoryStream input = new MemoryStream(inputData);
MemoryStream output = new MemoryStream();

Then you can use output.ToArray() afterwards to get a byte array out.

Note that it’s generally better to use using statements instead of a single try/finally block – as otherwise if the first call to Close fails, the rest won’t be made. You can nest them like this:

using (MemoryStream output = new MemoryStream())
using (Stream outZStream = new zlib.ZOutputStream(output))
using (Stream input = new MemoryStream(bytes))
{
    CopyStream(inFileStream, outZStream);
    return output.ToArray();
}