Help with Cast

Hi everyone,

I'm getting a warning when I try to do the (char *) cast on &buf, What is the correct cast for this?
The warning I get is : use of old-style cast

Thanks,
Ed.

Code:

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        char buf[3][20];
        inline void readInRow() {
                currentData.clear();
                mIn.read((char *) &buf, sizeof(buf));
                for (int i=0; i < 3; ++i)
                        currentData.push_back(string(buf[i]));
                printout(currentData);
                cout << endl;
        }

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Why can't you just pass it buf? I also dont think you can cast an array to a pointer...but if you could i believe the syntax would be (char **) for 2-d arrays.

I think istream::read() expects a char *, but you probably don't want to use &buf, but rather buf. And since this is C++, you should use

Code:

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mIn.read(reinterpret_cast<char *>(buf), sizeof(buf));

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Mats

Why not just pass buf[0] instead of forcing a 2D array to look like a 1D array?
Then you shouldn't need any casts.

Thanks matsp, that worked beautifully.

Quote:

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Why not just pass buf[0] instead of forcing a 2D array to look like a 1D array?

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Because with that matrix I want to represent 3 words of 20 characters max. I don't know how I would do that with a single array. I'm newbie sorry :)

Ed.

You got it right here:

Code:

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currentData.push_back(string(buf[i]));

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It's the same idea.

Quote:

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Originally Posted by afflictedd2

Thanks matsp, that worked beautifully.



Because with that matrix I want to represent 3 words of 20 characters max. I don't know how I would do that with a single array. I'm newbie sorry :)

Ed.

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If you are reading strings from a text-file, then istream::read will not do the right thing for you - you'd have to loop and use getline or >> to read the individual words.

--
Mats

Quote:

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Originally Posted by afflictedd2

Thanks matsp, that worked beautifully.



Because with that matrix I want to represent 3 words of 20 characters max. I don't know how I would do that with a single array. I'm newbie sorry :)

Ed.

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But then wouldn't this work?

Code:

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for ( int x = 0; x < 3; ++x )
    mIn.read( buf[x], sizeof(buf[x]) );

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Quote:

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Originally Posted by matsp

If you are reading strings from a text-file, then istream::read will not do the right thing for you - you'd have to loop and use getline or >> to read the individual words.

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Mats

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It works. It's from a binary file not a text file.

Quote:

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Originally Posted by afflictedd2

It works. It's from a binary file not a text file.

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That's fine then - it's just that I've seen quite a few posts where someone is trying to read a text-file using read (or write it using write) and then complaining that the code doesn't work right - usually pointing at some completely different portion of code [such as the output or calculations]. I was just making sure that you are doing things the way they are meant to be done.

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Mats