apphost-extract/src/apphost-extract/apphost-extract-v2/Util.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace apphost_extract_v2
{
    public static class Util
    {
        public static int[] PatternScan(FileStream fs, int start, int length, byte[] pattern, string mask)
        {
            byte[] scanBuffer = fs.ReadBuffer(start, length);

            List<int> scanResults = new List<int>();

            for(int i = 0; i < scanBuffer.Length - pattern.Length; i++)
            {
                if (!IsMatch(scanBuffer, i, pattern, mask))
                    continue;

                scanResults.Add(start + i);
            }

            return scanResults.ToArray();
        }


        //https://stackoverflow.com/a/283648/10724593
        private static bool IsMatch(byte[] array, int position, byte[] candidate, string mask)
        {
            if (candidate.Length > (array.Length - position))
                return false;

            for (int i = 0; i < candidate.Length; i++)
                if (mask[i] == 'x' && array[position + i] != candidate[i])
                    return false;

            return true;
        }

        public static byte[] ReadBuffer(this FileStream fs, long start, int length)
        {
            byte[] buff = new byte[length];
            fs.Seek(start, SeekOrigin.Begin);
            fs.Read(buff, 0, length);
            return buff;
        }
    }
}