(C is stricter: a function which is inline anywhere must be inline everywhere and must be defined identically in all the translation units that use it.) GNU C inline rules The GNU C rules are described in the GNU C manual, which is included with the compiler.
I have a small to medium project that is in C++/CLI. I really hate the syntax extensions of C++/CLI and I would prefer to work in C#. Is there a tool that does a decent job of translating one to the other?
EDIT: When I said Managed c++ before I apparently meant c++/CLI
5 Answers
You can only translate Managed C++ code (and C++/CLI code) to C# if the C++ code is pure managed. If it is not -- i.e. if there is native code included in the sources -- tools like .NET Reflector won't be able to translate the code for you.
If you do have native C++ code mixed in, then I'd recommend trying to move the native code into a separate DLL, replace your calls to DLL functions by easily identifiable stub functions, compile your project as a pure .NET library, then use .NET reflector to de-compile into C# code. Then you can replace the calls to the stub functions by p-invoke calls to your native DLL.
Good luck! I feel for you!
.NET Managed C++ is like a train wreck. But have you looked into C++ CLI? I think Microsoft did a great job in this field to make C++ a first class .NET citizen.
I'm not sure if this will work, but try using .Net Reflector along with ReflectionEmitLanguage plug-in. The RelelectionEmitLanguage plug-in claims to convert your assembly to c# code.
Back ~2004 Microsoft did have a tool that would convert managed C++ to C++/CLI ... sort of. We ran it on a couple of projects, but to be honest the amount of work left cleaning up the project was no less than the amount of work it would have been to do the conversion by hand in the first place. I don't think the tool ever made it out into a public release though (maybe for this reason).
I don't know which version of Visual Studio you are using, but we have managed C++ code that will not compile with Visual Studio 2005/2008 using the /clr:oldSyntax switch and we still have a relic VS 2003 around for it.
I don't know of any way of going from C++ to C# in a useful way ... you could try round tripping it through reflector :)
Such projects are often done in c++/cli because C# isn't really an elegant option for the task. e.g. if you have to interface with some native C++ libraries, or do very high performance stuff in low level C. So just make sure whoever chose c++/cli didn't have a good reason to do it before doing the switch.
Having said that, I'm highly skeptical there's something that does what you ask, for the simple reason that not all C++/cli code is translatable to C# (and probably vice versa too).
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The contents of file.txt are:
Where 5 3
is a coordinate pair.How do I process this data line by line in C++?
I am able to get the first line, but how do I get the next line of the file?
8 Answers
First, make an ifstream
:
The two standard methods are:
Assume that every line consists of two numbers and read token by token:
Line-based parsing, using string streams:
You shouldn't mix (1) and (2), since the token-based parsing doesn't gobble up newlines, so you may end up with spurious empty lines if you use getline()
after token-based extraction got you to the end of a line already.
Use ifstream
to read data from a file:
If you really need to read line by line, then do this:
But you probably just need to extract coordinate pairs:
Update:
In your code you use ofstream myfile;
, however the o
in ofstream
stands for output
. If you want to read from the file (input) use ifstream
. If you want to both read and write use fstream
.
Reading a file line by line in C++ can be done in some different ways.
[Fast] Loop with std::getline()
The simplest approach is to open an std::ifstream and loop using std::getline() calls. The code is clean and easy to understand.
[Fast] Use Boost's file_description_source
Another possibility is to use the Boost library, but the code gets a bit more verbose. The performance is quite similar to the code above (Loop with std::getline()).
[Fastest] Use C code
If performance is critical for your software, you may consider using the C language. This code can be 4-5 times faster than the C++ versions above, see benchmark below
Benchmark -- Which one is faster?
I have done some performance benchmarks with the code above and the results are interesting. I have tested the code with ASCII files that contain 100,000 lines, 1,000,000 lines and 10,000,000 lines of text. Each line of text contains 10 words in average. The program is compiled with -O3
optimization and its output is forwarded to /dev/null
in order to remove the logging time variable from the measurement. Last, but not least, each piece of code logs each line with the printf()
function for consistency.
The results show the time (in ms) that each piece of code took to read the files.
The performance difference between the two C++ approaches is minimal and shouldn't make any difference in practice. The performance of the C code is what makes the benchmark impressive and can be a game changer in terms of speed.
Since your coordinates belong together as pairs, why not write a struct for them?
Then you can write an overloaded extraction operator for istreams:
And then you can read a file of coordinates straight into a vector like this:
Expanding on the accepted answer, if the input is:
you will still be able to apply the same logic, like this:
This answer is for visual studio 2017 and if you want to read from text file which location is relative to your compiled console application.
first put your textfile (test.txt in this case) into your solution folder. After compiling keep text file in same folder with applicationName.exe
C:Users'username'sourcerepos'solutionName'solutionName'
This is a general solution to loading data into a C++ program, and uses the readline function. This could be modified for CSV files, but the delimiter is a space here.
Although there is no need to close the file manually but it is good idea to do so if the scope of the file variable is bigger:
protected by pmrFeb 15 '14 at 13:43
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