在C＃中读取C ++。 我知道我需要字节缓冲区，但还不足够

Question

hey everyone I am new to object oriented programming and I am trying to transfer some c++ code into c#. I am trying to translate:

fread(top,sizeof(int),16,stream);
first = top[1];
second = top[2];

and so on.....

where top is: static int top[16];

the stream file is a .eng file that I would like to convert to a .csv file. So I want to read the .eng file to convert it.

I currently have

if (fs.CanRead)
        {
            byte[] buffer = new byte[fs.Length]; 
            int bytesread = fs.Read(buffer, 0, buffer.Length);
            char[] CharTest = (Encoding.ASCII.GetChars(buffer, 0, bytesread));
            string bytesString = Encoding.ASCII.GetString(buffer, 0, bytesread); 
            Console.WriteLine(CharTest);
            //Console.WriteLine(bytesString);

            byte[] top = new byte[16];
            first = top[1];

so I am able to read my fs file and I have the charTest as the entire .eng file. Although on the c++ line it is separated into 16 tops. I do not understand how the c++ does this. I am mainly confused on the sizeof(int) part. I have the ability to read the entire file yet not sure where to separate to get the 16 and build the top array

Answer 1

Here's some documentation about fread :

http://en.cppreference.com/w/cpp/io/c/fread

So, fread s first argument is the place in memory into which the file will be read. The second is the size in bytes of each object that is read from the file, then the third is the number of objects. And the last is the stream.

For instance, fread(buffer, sizeof(double), 12, stream) , means read 12 objects the size of a double from stream into buffer.

static int header[16]; means an array of 16 ints with internal linkage (that last part isn't necessarily something you need to care about at this stage).

Answer 2

The code I would write is:

using (var fs = File.OpenRead("somefile.eng"))
using (var br = new BinaryReader(fs))
using (var csv = new StreamWriter("output.csv", false, Encoding.ASCII))
{
    // Note that the array is useless, because we write the csv
    // one int at a time!
    int[] row = new int[16];

    while (true)
    {
        // used for skipping the ; at before the first element
        bool first = true;

        // Note that the file must be composed of only
        // blocks of 16 int32 . No dangling byte
        for (int i = 0; i < 16; i++)
        {
            row[i] = br.ReadInt32();

            // You are skipping top[0]
            if (i == 0)
            {
                continue;
            }

            // No ; before the first element
            if (first)
            {
                first = false;
            }
            else
            {
                csv.Write(';');
            } 

            csv.Write(row[i]);
        }

        // End of file
        if (br.PeekChar() == -1)
        {
            break;
        }

        csv.WriteLine();
    }
}

There is a quite good BinaryReader class that can be used for reading binary data from a Stream (file in this case). Then you can write the csv by using the StreamWriter class.

Normally at this point I'd throw a tirade about Encoding.ASCII and about writing manually a CSV file instead of using a library, but this being a numerical only CSV then it isn't too much a bad thing to do as written.