Replace sequence of bytes in binary file

Question

What is the best method to replace sequence of bytes in binary file to the same length of other bytes? The binary files will be pretty large, about 50 mb and should not be loade

Answer 1

My solution :

    /// 

    /// Copy data from a file to an other, replacing search term, ignoring case.
    /// 
    /// 
    /// 
    /// 
    /// 
    private static void ReplaceTextInBinaryFile(string originalFile, string outputFile, string searchTerm, string replaceTerm)
    {
        byte b;
        //UpperCase bytes to search
        byte[] searchBytes = Encoding.UTF8.GetBytes(searchTerm.ToUpper());
        //LowerCase bytes to search
        byte[] searchBytesLower = Encoding.UTF8.GetBytes(searchTerm.ToLower());
        //Temporary bytes during found loop
        byte[] bytesToAdd = new byte[searchBytes.Length];
        //Search length
        int searchBytesLength = searchBytes.Length;
        //First Upper char
        byte searchByte0 = searchBytes[0];
        //First Lower char
        byte searchByte0Lower = searchBytesLower[0];
        //Replace with bytes
        byte[] replaceBytes = Encoding.UTF8.GetBytes(replaceTerm);
        int counter = 0;
        using (FileStream inputStream = File.OpenRead(originalFile)) {
            //input length
            long srcLength = inputStream.Length;
            using (BinaryReader inputReader = new BinaryReader(inputStream)) {
                using (FileStream outputStream = File.OpenWrite(outputFile)) {
                    using (BinaryWriter outputWriter = new BinaryWriter(outputStream)) {
                        for (int nSrc = 0; nSrc < srcLength; ++nSrc)
                            //first byte
                            if ((b = inputReader.ReadByte()) == searchByte0
                                || b == searchByte0Lower) {
                                bytesToAdd[0] = b;
                                int nSearch = 1;
                                //next bytes
                                for (; nSearch < searchBytesLength; ++nSearch)
                                    //get byte, save it and test
                                    if ((b = bytesToAdd[nSearch] = inputReader.ReadByte()) != searchBytes[nSearch]
                                        && b != searchBytesLower[nSearch]) {
                                        break;//fail
                                    }
                                    //Avoid overflow. No need, in my case, because no chance to see searchTerm at the end.
                                    //else if (nSrc + nSearch >= srcLength)
                                    //    break;

                                if (nSearch == searchBytesLength) {
                                    //success
                                    ++counter;
                                    outputWriter.Write(replaceBytes);
                                    nSrc += nSearch - 1;
                                }
                                else {
                                    //failed, add saved bytes
                                    outputWriter.Write(bytesToAdd, 0, nSearch + 1);
                                    nSrc += nSearch;
                                }
                            }
                            else
                                outputWriter.Write(b);
                    }
                }
            }
        }
        Console.WriteLine("ReplaceTextInBinaryFile.counter = " + counter);
    }