C # Replace HEX in binary

Question

I have a binary file where several values ​​need to be changed. More precisely, in the two parts of the file at the beginning there are two HEX values

66 73 69 6D 35 2E 36 39

what should be changed to

4D 53 57 49 4E 34 2E 31

How can I do this async and as quickly as possible? I went so far as to read the entire file into the byte [] array, but this class does not have a search or replace function.

Answer 1

Here is a method that I wrote that you can use to find where the byte[]bytes you are trying to find are in yours .

/// <summary>
/// Searches the current array for a specified subarray and returns the index
/// of the first occurrence, or -1 if not found.
/// </summary>
/// <param name="sourceArray">Array in which to search for the
/// subarray.</param>
/// <param name="findWhat">Subarray to search for.</param>
/// <param name="startIndex">Index in <paramref name="sourceArray"/> at which
/// to start searching.</param>
/// <param name="sourceLength">Maximum length of the source array to search.
/// The greatest index that can be returned is this minus the length of
/// <paramref name="findWhat"/>.</param>
public static int IndexOfSubarray<T>(this T[] sourceArray, T[] findWhat,
        int startIndex, int sourceLength) where T : IEquatable<T>
{
    if (sourceArray == null)
        throw new ArgumentNullException("sourceArray");
    if (findWhat == null)
        throw new ArgumentNullException("findWhat");
    if (startIndex < 0 || startIndex > sourceArray.Length)
        throw new ArgumentOutOfRangeException();
    var maxIndex = sourceLength - findWhat.Length;
    for (int i = startIndex; i <= maxIndex; i++)
    {
        if (sourceArray.SubarrayEquals(i, findWhat, 0, findWhat.Length))
            return i;
    }
    return -1;
}

/// <summary>Determines whether the two arrays contain the same content in the
/// specified location.</summary>
public static bool SubarrayEquals<T>(this T[] sourceArray,
        int sourceStartIndex, T[] otherArray, int otherStartIndex, int length)
        where T : IEquatable<T>
{
    if (sourceArray == null)
        throw new ArgumentNullException("sourceArray");
    if (otherArray == null)
        throw new ArgumentNullException("otherArray");
    if (sourceStartIndex < 0 || length < 0 || otherStartIndex < 0 ||
        sourceStartIndex + length > sourceArray.Length ||
        otherStartIndex + length > otherArray.Length)
        throw new ArgumentOutOfRangeException();

    for (int i = 0; i < length; i++)
    {
        if (!sourceArray[sourceStartIndex + i]
            .Equals(otherArray[otherStartIndex + i]))
            return false;
    }
    return true;
}