How to find and replace a large section of bytes in a file?

Question

I'm looking to find a large section of bytes within a file, remove them and then import a new large section of bytes starting where the old ones started.

Here's a video of the manual process that I'm trying to re-create in C#, it might explain it a little better: https://www.youtube.com/watch?v=_KNx8WTTcVA

I have only basic experience with C# so am learning as I go along, any help with this would be very appreciated!

Thanks.

score 1 · Answer 1 · edited May 23 '17 at 12:17

Refer to this question: C# Replace bytes in Byte[]

Use the following class:

public static class BytePatternUtilities
{
    private static int FindBytes(byte[] src, byte[] find)
    {
        int index = -1;
        int matchIndex = 0;
        // handle the complete source array
        for (int i = 0; i < src.Length; i++)
        {
            if (src[i] == find[matchIndex])
            {
                if (matchIndex == (find.Length - 1))
                {
                    index = i - matchIndex;
                    break;
                }
                matchIndex++;
            }
            else
            {
                matchIndex = 0;
            }

        }
        return index;
    }

    public static byte[] ReplaceBytes(byte[] src, byte[] search, byte[] repl)
    {
        byte[] dst = null;
        byte[] temp = null;
        int index = FindBytes(src, search);
        while (index >= 0)
        {
            if (temp == null)
                temp = src;
            else
                temp = dst;

            dst = new byte[temp.Length - search.Length + repl.Length];

            // before found array
            Buffer.BlockCopy(temp, 0, dst, 0, index);
            // repl copy
            Buffer.BlockCopy(repl, 0, dst, index, repl.Length);
            // rest of src array
            Buffer.BlockCopy(
                temp,
                index + search.Length,
                dst,
                index + repl.Length,
                temp.Length - (index + search.Length));


            index = FindBytes(dst, search);
        }
        return dst;
    }
}

Usage:

byte[] allBytes = File.ReadAllBytes(@"your source file path");
byte[] oldbytePattern = new byte[]{49, 50};
byte[] newBytePattern = new byte[]{48, 51, 52};
byte[] resultBytes = BytePatternUtilities.ReplaceBytes(allBytes, oldbytePattern, newBytePattern);
File.WriteAllBytes(@"your destination file path", resultBytes)

The problem is when the file is too large, then you require a "windowing" function. Don't load all the bytes in memory as it will take up much space.

How to find and replace a large section of bytes in a file?

1 Answers1