C 样式，C++ 流或 Win32 API 文件 I/O？

Question

I read C++ Streams vs. C-style IO? (amongst other pages) to try to help me decide which way to implement some file IO in a project I'm working on.

Background I'm fairly new to C++ and Windows programming, I've traditionally worked in C and command line applications. Apologies ahead of time for the n00b-ness of this question.

The problem I want to read one text file, process the contents and output to another (new) text file. I am working in a Win32 environment (and this won't change for the forseeable future) and am writing the application to be Unicode aware, through _T style macros. The "processing" could include inserting/appending/deleting the lines of text, which will be at most 128 characters.

The question I would prefer to write something that is going to be robust, so I/O error handling is a consideration. I think that I need to stay away from C style file I/O if for no other reason than to simplify the code and type checking -- ie approach this in a more OO POV. What are the advantages of using Win32 API functions over the C++ stream functions (if any)? Can you recommend a good primer for either approach? (My googling has left me with a little information overload)

Thanks muchly

Answer 1

What are the advantages of using Win32 API functions over the C++ stream functions (if any)?

1. Speed
2. Ability to use overlapped I/O to handle multiple operations at once without threads (and the complexity of synchronization)
3. Speed
4. More specific error codes
5. Speed
6. Speed
7. Low dependency footprint (compared to MSVC++ 7.x, 8.0, 9.0, 10.0 and probably most other vendors)
8. Speed

Answer 2

Use C++ stream I/O. Writing to text files is hardly going to stress the I/O library, and you gain enormous benefits in clarity of code, type safety, and the fact that you hardly have to write anything to get the job done. As a side effect, your code will probably be more portable and more understandable, so if you have to ask about it here, you will get more good answers.

Answer 3

To take a broader look, direct use of Win32 is good if you need a tiny application with no additional dependencies.

For anything that C++ iostreams does better, you probably want to look at Boost::Spirit. Seems like it has all the type-safety of iostreams, with much better performance.

You really have two problems here: File I/O, and Text Processing. Win32 does the first exceptionally well, and provides no help with the second. Boost::Spirit does the second very well. C++ iostreams are marginal at both tasks, avoid them unless portability is the most important feature.

Answer 4

Just to provide a rough benchmark - this code, which must be about the most inefficient possible:

#include <iostream>
using namespace std;

unsigned int MB = 1024 * 1024;
unsigned int GB = MB * 1024;

int main() {
    char c = 'x';
    for ( unsigned int i = 0; i < GB; i++ ) {
        cout << c;
    }
}

Took about 4 minutes to write a gig of data to a text file when invoked as:

myprog > file.txt

on my hardly state-of-the-art laptop.