Problems with copying strings

This is a discussion on Problems with copying strings within the C++ Programming forums, part of the General Programming Boards category; Ok, so I am working at a program that operates with sets. Each set has a name and an array ...

  1. #1
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    Problems with copying strings

    Ok, so I am working at a program that operates with sets. Each set has a name and an array for its elements. The user inputs for example "Alpha: 1 2 3 4 5", where Alpha is the name. I have to parse the string so that I get what's before the : symbol. It works perfectly with name declared as static (such as char name[10]), but when I am allocating memory for exactly as many characters as there are before the : , then I get either errors, either "Press any key to continue"... I used strncpy and also a function implemented by myself, but to no use.

    Does anyone have another idea for implementing this? Thank you.

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    Code:
     class CMultime
    {
    	int* m_Elemente;
    	char* m_Nume;
    public:
    	void preiaNume(char* sursa)
    	{
    		int caractere = 0;
    		int lungime = strlen(sursa);
    		for(int i = 0; i < lungime; i++)
    		{
    			if(sursa[i] != ':')
    			{
    				caractere++;
    			}
    			else
    			{
    				break;
    			}
    		}
    		if(caractere)
    		{
    			m_Nume = new char[ caractere ];
    			for(int i = 0; i < caractere; i++)
    				*(m_Nume + i) = *(sursa + i);
    		}
    		else
    		{
    			cout << "Nu ai respectat formatul sau nu ai introdus numele multimii." << endl;
    		}
    	}
    This would be it. After using a function to display m_Nume, I get the string before : and some ASCII weird stuff.

  4. #4
    spurious conceit MK27's Avatar
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    Quote Originally Posted by Veneficvs View Post
    Code:
     
    			m_Nume = new char[ caractere ];
    			for(int i = 0; i < caractere; i++)
    				*(m_Nume + i) = *(sursa + i);
    This would be it. After using a function to display m_Nume, I get the string before : and some ASCII weird stuff.
    You need to null terminate this string.
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    Quote Originally Posted by MK27 View Post
    You need to null terminate this string.
    Thank you! This is the modified version.
    Code:
    for(i = 0; i < caractere; i++)
    				*(m_Nume + i) = *(sursa + i);
    			*(m_Nume + i) = NULL;
    Now, the main has
    Code:
     void main()
    {
    	CMultime prima;
    	char sir[10];
    	cin.getline(sir, 10);
    	prima.preiaNume(sir);
    	prima.afis();
    }
    . It compiles great, it even gets me the string, but I hear a sound and the program does not stop. But thank you very much.. I forgot about that NULL ending.

  6. #6
    C++ Witch laserlight's Avatar
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    I suggest that you change m_Elemente to be a std::vector<int>, and change m_Nume to be a std::string. The parameter named sursa looks like it should be a const char* instead, though if you go with my suggestion then it might as well be a const std::string&.

    By the way, it would be good if you would translate your code to English.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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    Sorry. From now on I will translate it. I found the problem myself. It is because when I say *(m_Nume + i) = NULL, it puts the NULL into the next element.. which does not belong to the string because of the dimension. Therefore, I make new char [caractere + 1] instead. Thank you for all your replies.

  8. #8
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by Veneficvs
    I found the problem myself. It is because when I say *(m_Nume + i) = NULL, it puts the NULL into the next element.. which does not belong to the string because of the dimension. Therefore, I make new char [caractere + 1] instead.
    Good to hear that, but unless you have special reasons for doing otherwise, you should still prefer using std::string in this case. If not, it looks like you are going to have to manually manage the memory for two things, and you're probably going to get it wrong.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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