returning a *string and string[] from a function

[robUK2]

Hello,

This might be better explained with my code below. if you are return a *string or a string[].

The idea is to convert the whole string to upper case without depending on any other libraries.

However, if the user passes in a *string or a string[] would it depend on how I return them to the calling function. This is what I am experimenting with here.

I thought if I new what was being used, I could return based on that.

Any corrections that are needed for my code, please advise.

Many thanks,

char* ToUpper(char *str, const int length)
{
	char *reset = str; //For reseting the pointer to point to the ordinal address.
	int character;
	char *destString = malloc(length * sizeof(char));
	int i = 0;

	//Check to see if actual memory was allocated.
	if(destString == NULL)
	{
		return NULL;
	}

	//Copy the contents to the array. 
	//A pointer to an array cannot be modified
	while(*str)
	{
		destString[i] = *str++;
		i++;
	}
	destString[i] = '\0'; //Terminate the end of the string.

	str = reset; //Reset the pointer to point to the first character in the character array.

	i = 0;
	while(*str)
	{
		//Get the character and subtract 32 to make it upper case.
		//Filter for only lower case characters.
		if(*str >= 97 && *str <= 122)
		{	
			//Get the character that is lower case and subtrack 32 to make it a upper case character
			character = (int) destString[i];
			character -= 32;
			//Assign the upper case character back into its position in the array.
			destString[i] = (char) character;
		}	
		str++;	
		i++;
	}

	destString[i] = '\0';
	//Point the character array about to the first character in the array.
	//str = reset; 
	str = destString;

	return destString;
}


int main(int argc, char** argv)
{
	char *string1 = "Hello how are you today?";
	char string2[] = "Hello how are you today?";

	string1 = ToUpper(string1, strlen(string1));
	printf("string1: %s\n", string1);
	string2[0] = ToUpper(string2, strlen(string2));
	printf("string2: %s\n", string2);

	return 0;
}

 

[xwb]

You need to malloc length+1. strlen returns the number of characters excluding the terminator.

 

[cpjust]

Since ToUpper() returns a pointer to newly allocated memory, the caller needs to remember to free() that memory.

//Get the character and subtract 32 to make it upper case.
//Filter for only lower case characters.
if(*str >= 97 && *str <= 122)
{
    //Get the character that is lower case and subtrack 32 to make it a upper case character
    character = (int) destString[i];
    character -= 32;
    //Assign the upper case character back into its position in the array.
    destString[i] = (char) character;
}

This is NOT portable.
Use the toupper() function if you want portable code.

 

[jdu2006]

The codes may be reduced. you don't need destString and you should get length as a stopper of while loop. Be carefully coding in C, don't let memory leak.