求兼容Microsoft Visual C++2008的CString连续4位数字替换函数

Since Visual C++ 2008 has really limited regex support (the standard <regex> header wasn't fully implemented until later MSVC versions), a custom string traversal approach is the most reliable way to handle this without external dependencies. Below is a function that works seamlessly with MFC's CString and fits your exact requirements:

CString ReplaceConsecutiveFourDigits(CString input)
{
    CString result;
    int currentDigitRunLength = 0;
    int digitRunStartPos = -1;

    for (int i = 0; i < input.GetLength(); ++i)
    {
        TCHAR currentChar = input[i];
        if (_istdigit(currentChar))
        {
            if (currentDigitRunLength == 0)
            {
                // Mark the start of a new sequence of digits
                digitRunStartPos = i;
            }
            currentDigitRunLength++;
        }
        else
        {
            // We've hit a non-digit; process the current digit sequence if there is one
            if (currentDigitRunLength > 0)
            {
                if (currentDigitRunLength >= 4)
                {
                    // Replace first 4 digits with ****, append remaining digits
                    result += _T("****");
                    result += input.Mid(digitRunStartPos + 4, currentDigitRunLength - 4);
                }
                else
                {
                    // Keep short digit sequences as-is
                    result += input.Mid(digitRunStartPos, currentDigitRunLength);
                }
                // Reset tracking variables for next sequence
                currentDigitRunLength = 0;
                digitRunStartPos = -1;
            }
            // Add the non-digit character to the result
            result += currentChar;
        }
    }

    // Handle the edge case where the string ends with a digit sequence
    if (currentDigitRunLength > 0)
    {
        if (currentDigitRunLength >= 4)
        {
            result += _T("****");
            result += input.Mid(digitRunStartPos + 4, currentDigitRunLength - 4);
        }
        else
        {
            result += input.Mid(digitRunStartPos, currentDigitRunLength);
        }
    }

    return result;
}

How It Works #

• Tracking Digit Sequences: We traverse each character in the input CString, keeping track of when we enter a sequence of digits, its start position, and its length.
• Processing Sequences: When we hit a non-digit character (or reach the end of the string), we check the length of the current digit sequence:
  • If it's 4 or more digits long: We append **** followed by any digits beyond the first 4.
  • If it's shorter than 4 digits: We append the entire sequence as-is.
• Compatibility: Uses _istdigit (a VC-compatible macro that works for both Unicode and ANSI builds) and standard CString methods (GetLength, Mid) that are fully supported in VC2008.

Test It With Your Example #

If you pass your sample input:

CString original = _T("1234567 12 34 78 iioi78ccc8888 aaassd dededeed ed");
CString processed = ReplaceConsecutiveFourDigits(original);

The processed string will be exactly what you need:
****567 12 34 78 iioi78ccc**** aaassd dededeed ed

Notes #

• This works for both MFC and ATL CString implementations, since both have the required methods.
• No external libraries or regex dependencies are needed—perfect for legacy VC2008 projects.

内容的提问来源于stack exchange，提问作者Dan.Gurghian