How Can I Efficiently Find a Byte Pattern Within a Byte Array in C#?

C# byte array pattern search

Determining the position of the specified byte pattern in the provided byte array can be achieved using a variety of efficient methods.

Use Locate method

A straightforward approach is to use the Locate method, as shown in the following C# code snippet:

static int[] Locate(this byte[] self, byte[] pattern)
{
    if (IsEmptyLocate(self, pattern))
        return Empty;

    var list = new List<int>();

    for (int i = 0; i < self.Length; i++)
    {
        if (IsMatch(self, pattern, i))
        {
            list.Add(i);
        }
    }

    return list.ToArray();
}

This method first checks for empty input or invalid search criteria. If these conditions are met, an empty array is returned. Otherwise, it iterates over the input array and uses the IsMatch helper method to check if the pattern matches at each position. The positions where a match is found are stored in a list and returned as an array.

Use SearchBytePattern method

Alternatively, you may consider using the SearchBytePattern method. It also provides functionality for efficient pattern matching on byte arrays:

public static List<int> SearchBytePattern(byte[] byteArray, List<byte> bytePattern)
{
    int start = -1;
    List<int> matches = new List<int>();

    for (int i = 0; i < byteArray.Length; i++)
    {
        if (byteArray[i] == bytePattern[0])
        {
            start = i;
            bool match = true;
            for (int j = 1; j < bytePattern.Count; j++)
            {
                if (i + j >= byteArray.Length || byteArray[i + j] != bytePattern[j])
                {
                    match = false;
                    break;
                }
            }
            if (match)
            {
                matches.Add(start);
            }
        }
    }

    return matches;
}

In this implementation, the method receives a byte array and a byte pattern as input, and maintains a starting position for potential matches. It iterates through the array, checking whether the byte at each position matches the corresponding byte in the pattern. When an exact match is found, it adds the starting position of the match to the list of matching positions.

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