I need help with text replacement in C++ using Windows API functions. I want to scan through a file and replace every occurrence of a specific text pattern with different text. This seems straightforward in other programming languages, but I’m struggling to figure out the right approach in C++. I’m working on a custom action for Windows Installer XML (WiX), so I don’t need cross-platform compatibility. I just want the easiest method to accomplish this task. Can someone show me how to read a file, find all instances of a target string, replace them with new content, and write the modified data back to the file? I’m specifically looking for a solution that uses native Windows API calls rather than third-party libraries.
Memory mapping with CreateFileMapping and MapViewOfFile is way more efficient for text replacement, especially on larger files. You don’t have to load everything into heap memory at once. Open your file with CreateFile using GENERIC_READ | GENERIC_WRITE access, create a file mapping object, then map it into your process’s address space. Now you can search and replace strings directly on the mapped memory. When you’re done, use FlushViewOfFile to write changes to disk before unmapping. This beats traditional read/write operations and works great with Windows Installer custom actions.
To perform text replacement using the Windows API, you can employ the CreateFile, ReadFile, and WriteFile functions effectively. Start by opening your target file with the necessary read and write permissions. Use GetFileSize to determine how much memory you need for the file’s content. After loading the entire file into memory with ReadFile, implement string replacement using standard C++ functions. Finally, write the modified content back to the file with WriteFile. If your changes affect the file size, remember to call SetEndOfFile after writing to ensure the file structure is correct. Utilizing the Windows API in this way allows for precise manipulation, especially in WiX scenarios.
for multiple files, u can use FindFirstFile/FindNextFile, but for just one file replace, start with CreateFile. then loop - ReadFile in chunks, run std::string::replace on each chunk, then WriteFile back. be careful with overlaps at buffer edges, that’s where many mess up.