Remove '\n.\n' C++

If i have a string as such

"I am not here... \n..Hello\n.\n....Whats happening"

I want to replace the above string so:

"I am not here... \n..Hello\n. \n....Whats happening"
                              ^ Space added

Just a bit of a background on what im doing. Im using sendmail in C++ and \n.\n is End Of Message Equivalent of sendmail. I just created a class that uses sendmail to send mails. but obviously if the user from the outsite gives sendmail that command i want it to be removed. Here is my message function just incase.:

//Operator to add to the message
void operator<<(string imessage){
    if (imessage != ""){ message += imessage; } 
}

How would i go about doing this. Thanks in ad开发者_如何学Govance :D

This is my last version :)
This code handles the case mentioned by @Greg Hewgill

string& format_text(string& str)
{
    const string::size_type dot_offset = 2;
    string::size_type found_at_start = str.find("\n.\n"),
                    found_at = str.find("\n.\n");

    if(found_at_start != string::npos)
        str.insert(0, " ");

    while(found_at != string::npos)
    {
        str.insert(found_at+dot_offset+1, " ");
        found_at = str.find("\n.\n", found_at+1);
    }
    return str;
}

int main()
{
    string text = ".\nn\n.\nn";
    std::cout << format_text(text);
}

Look up String.find and String.replace

For example (not tested)

string endOfMessage = "\n.\n";
string replacement = "\n. \n";
size_t position;

while (position = message.find(endOfMessage))
{
   message.replace(position, endOfMessage.length(), replacement);
}

This is derived from Dan McG's answer so upvote him ;)

string endOfMessage = "\n.\n";
string replacement = "\n. \n";
size_t position;

while (position = message.find(endOfMessage, position) != message.npos)
{
   message.replace(position, endOfMessage.length(), replacement);
   position += replacement.length();
}

Boost has Boost.Regex (a regular expression module). Might be overkill if this is the only replacement you need to do.

Use std::search and the insert method of sequence containers such as string, deque, or whatever you use to store the message text.

typedef std::string::iterator SIter; // or whatever container you use
static const char *end_seq = "\n.\n";
for ( SIter tricky_begin = msg.begin();
  tricky_begin = std::search( tricky_begin, msg.end(), end_seq, end_seq+3 ),
  tricky_begin != msg.end(); ) {
    tricky_begin = msg.insert( tricky_begin + 2, ' ' );
}