read bytes from byte array

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i have a byte array of 678560 size.

i want to read data from 0th index to 10478.

is anyway to read data from specified position to length of data.

i wrote code for that but i tried in Google but didn't get perfect answer.

C#

using (StreamReader r = new StreamReader(path))
{
   string Readalltextofdata = r.ReadToEnd();
   byte[] readalltextofdataintobytes = StringToByteArray(Readalltextofdata);


}

     public static byte[] StringToByteArray(String hex)
        {
            int NumberChars = hex.Length;
            byte[] bytes = new byte[NumberChars / 2];
            for (int j = 0; j < NumberChars; j += 2)
                bytes[j / 2] = Convert.ToByte(hex.Substring(j, 2), 16);
            return bytes;
        }

so in readalltextofdataintobytes created and size is 678560. now from this byte array i want to read from 0th position to 10478.

thanks in advance.

Posted 19-Nov-13 2:14am

bunty swapnil

Updated 19-Nov-13 2:47am

phil.o

v3

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Comments

CPallini 19-Nov-13 8:22am

If you need only the first 10479 bytes then why don't you read just them from the file?

bunty swapnil 19-Nov-13 8:28am

i file i want to read in two parts.
and in my scenario file is already opened.i can not open it again. so i read only through stream reader. and then using readtoend store bi file in a string. after that through string to byte array make a pair of 2 char and convert it into bytes.

so i have byte array readalltextofdataintobytes. and if i will change my code i have to change more functionality.
even i use this code also.

array.copy(readalltextdataintobytes,internalbuffer,10478);

but giving eror value can not be null.

2 solutions

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Fredrik Bornander · Answer 1 · 2013-11-19T02:49:00

Solution 1

Use Linq

C#

var someBytes = readalltextofdataintobytes.Take(10478).ToArray();

You can also use Skip to skip ahead past the bytes you don't want to read.

Hope this helps,
Fredrik

Posted 19-Nov-13 2:49am

Fredrik Bornander

Ron Beyer · Answer 2 · 2013-11-19T02:54:00

Solution 2

Actually the most efficient way to do this, aside from pinning and unsafe code, is to use the Buffer.BlockCopy[^] method.

In your case, it would be:

C#

byte[] source = //...
byte[] byteSection = new byte[10478];
Buffer.BlockCopy(source, 0, byteSection, 0, byteSection.Length);

That way to copy more/less data just change the size of the byteSection array.

Posted 19-Nov-13 2:54am

Ron Beyer

Comments

bunty swapnil 19-Nov-13 10:19am

i wrote Buffer.BlockCopy(source, 66680, byteSection, 0, byteSection.Length)
its not woking. byte section. this size and index will change.

for example i have byte array of 10 and i destination array i want to read from 4th to 9th.

can you clear the above code.

Ron Beyer 19-Nov-13 10:25am

The second parameter is the starting point in the source array to begin taking data out, are you really wanting to start at the 66680 byte?

If you have a byte array of 10, and you want 4 to 9, here is what you would do:

byte[] source = new byte[10];
byte[] destination = new byte[6];
Buffer.BlockCopy(source, 4, destination, 0, destination.Length);

Which will copy 6 bytes (4 through 9) from source and put them in destination.