Thread: finding size of char*

I have been struggling for a long time trying different sizeof algorithms ive made up to find out how many objects are in the array. How can i do this??? I used sample code from charlez petzolds book and i have used the same algorithm and it works in his but not mine. so please help.

for finding the size of a char, include the string.h or cstring lib and use the function:

Code:

int strlen(const char *string);

example

Code:

char string[30] = "Hello World";
cout<<"The char is "<<strlen(string)<<" characters long"<<endl;

Originally Posted by JoshR

I have been struggling for a long time trying different sizeof algorithms ive made up to find out how many objects are in the array. How can i do this??? I used sample code from charlez petzolds book and i have used the same algorithm and it works in his but not mine. so please help.

basiclly you cant' in most of the times..

Code:

char b[10];
sizeof(b) returns sizeof(char) which is 1 times 10

int f(char b[]){return sizeof(b);}
f(b) returns sizeof(char*) because only a pointer is passed, and not the whole array.

char *c = new char[10];
sizeof(c) returns sizeof(char*), usually a 32 bits memory adress

So you'll have to keep track of the number of elements stored.

1) When you declare an array, you have to know the size to begin with. For instance,

Code:

const int size = 3;
double myArray[size] = {1.5, 2.5, 3.5};
cout<<"The size of the array is: "<<size<<endl;

If you want to send the array to a function and inside the function you need to know the size, then you should define the function to also accept the size of the array. For instance,

Code:

void myFunc(double anArray[], int size)
{
	for(int i = 0; i<size; i++)
	{
		cout<<anArray[i]<<endl;
	}
}

2) If you insist on using sizeof to get the size of the array, you can use an expression like this:

sizeof arrayName/sizeof arrayName[0]

For instance,

Code:

#include <iostream>
using namespace std;

class Apple
{
public:
	int weight;
};

int main ()
{
	const int size = 3;
	Apple appleArray[size];
	
	for(int i = 0; i < sizeof appleArray/sizeof appleArray[0]; i++)
	{
		appleArray[i].weight = i+1;
	}

	for(i= 0; i < sizeof appleArray/sizeof appleArray[0]; i++)
	{
		cout<<appleArray[i].weight<<endl;
	}

	return 0;
}