How to read int array from binary file c#

Question

I have the following code:

LZW lzw = new LZW();
int[] a = lzw.Encode(imageBytes);

FileStream fs = new FileStream("image-text-16.txt", FileMode.Append);
BinaryWriter w = new BinaryWriter(fs);

for (int i = 0; i < a.Length; i++)
{
   w.Write(a[i]);

}

w.Close();
fs.Close();

How to read array elements from the file? I tried several ways. For example, I wrote the length of the array to the file, and I tried to read the number. However, I had failed.

Note. I need to get the int array.

Answer 1

Are you looking for this:

var bytes = File.ReadAllBytes(@"yourpathtofile");

Or more something like:

        using (var filestream = File.Open(@"C:\apps\test.txt", FileMode.Open))
        using (var binaryStream = new BinaryReader(filestream))
        {
            for (var i = 0; i < arraysize; i++)
            {
                Console.WriteLine(binaryStream.ReadInt32());
            }
        }

Or, a small example with unit tests:

Create a binary file with integers...

    [Test]
    public void WriteToBinaryFile()
    {
        var ints = new[] {1, 2, 3, 4, 5, 6, 7};

        using (var filestream = File.Create(@"c:\apps\test.bin"))
        using (var binarystream = new BinaryWriter(filestream))
        {
            foreach (var i in ints)
            {
                binarystream.Write(i);
            }
        }
    }

And a small example test of reading from a binary file

    [Test]
    public void ReadFromBinaryFile()
    {
        // Approach one
        using (var filestream = File.Open(@"C:\apps\test.bin", FileMode.Open))
        using (var binaryStream = new BinaryReader(filestream))
        {
            var pos = 0;
            var length = (int)binaryStream.BaseStream.Length;
            while (pos < length)
            {
                var integerFromFile = binaryStream.ReadInt32();
                pos += sizeof(int);
            }
        }
    }

Another approach of reading from binary file

    [Test]
    public void ReadFromBinaryFile2()
    {
        // Approach two
        using (var filestream = File.Open(@"C:\apps\test.bin", FileMode.Open))
        using (var binaryStream = new BinaryReader(filestream))
        {
            while (binaryStream.PeekChar() != -1)
            {
                var integerFromFile = binaryStream.ReadInt32();
            }
        }
    }

Answer 2

I'd say the other way around. Only thing is you don't know the size before reading it, so calculate that first. Oh and I'd use 'using' to make sure things are disposed (and closed) properly:

        int[] ll;
        using (FileStream fs = File.OpenRead("image-text-16.txt"))
        {
            int numberEntries = fs.Length / sizeof(int);
            using (BinaryReader br = new BinaryReader(fs))
            {
                ll = new int[numberEntries];
                for (int i = 0; i < numberEntries; ++i)
                {
                    ll[i] = br.ReadInt32();
                }
            }
        }
        // ll is the result

The thing I don't really understand is why you're writing an int[] from LZW, but I guess there's a reason for that...