Thread: sizeof() EZ question

Hi everyone!!

Got a little problem...

First I'm passing out as a char array the following variable :

Code:

Edit1->Text.c_str()

Edit1 being a TEdit.
So I'm passing it to a second function that gets it and is supposed to give it's size by executing the following code :

Code:

int Length = sizeof(String);
ShowMessage(AnsiString(Length));

(String is the variable name I gave to the char array coming into the second function) (also, I know there's no goal by this program, this is just a test on a bigger one )
But what the message box is always showing out is "3"... Whatever I put in the TEdit's it's always 3 that is shown in the msgbox; any idea?

Thx in advance!!!

VV
[email protected]

>But what the message box is always showing out is "3"

sizeof(String), where String is a char*, is going to return the memory used to hold a pointer (not the memory size of what it points to). This would be 4 on under a 32bit environment, as in 4 bytes. Don't know why you're finding it to be 3.

If you want the size need for a char* array, do the following:

Code:

int Length = strlen(String) + 1;
ShowMessage(Length);

A char is always 1 byte. The +1 is to take account of the NULL terminator.

yup, okay, thanks for the info about the fact that sizeof was getting only the pointer's size...
it helped...

but BTW... now I'm wanting a way to know the number of integer an array that is passed to that function contains... I know an integer is two byte...

so it should return me .. say 20 if there was 10 integers in it... obviously it returns me 2 cauz I did the same error I did with my char array up this page.

So how should I proceed to know how many integers are on an integer array then?!!??! how do I bring sizeof to calculate not only the size of the pointer but the size of the data stocked under the pointer?!?!

Thx in advance!!

VV

An integer is 4 bytes. A short is 2 bytes.

Here is some information on getting number of elements in an array

Code:

// Assuming proper headers and such..

#define SSIZE(n)     sizeof(n)/sizeof(n[0])

int nArray[ 4 ] = { 1, 2, 3, 4 };

cout << SSIZE(nArray) << " Elements in the array" << endl;

cout << "One element is " << sizeof( nArray[0] ) << " bytes long" << endl;

cout << "The entire array is " << sizeof( nArray ) << " bytes long" << endl;

The SSIZE macro takes the size in bytes of the entire array and divides out the size of an individual element to determine the number of total elements. Hope this helps you.

ohh.. this is fun

hehe thanks a lot!
I'll try this!

see ya l8r!

VV

Originally posted by V1P3R V3N0M
Returns one.... here's a paste of a part of the code so it could maybe give a clue...

Code:

#define SSIZE(n) sizeof(n)/sizeof(n[0])

int SortInt(int *Array)
{
  int Temp;

  int Length = SSIZE(Array);


  ShowMessage(AnsiString(Length));

Gives always "1" now...

Any other idea???

BTW, this is how my int array is declared in another function :

Code:

  int Array[] = {StringToInt(Edit1->Text.c_str()), StringToInt(Edit2->Text.c_str()),
                 StringToInt(Edit3->Text.c_str()), StringToInt(Edit4->Text.c_str()),
                 StringToInt(Edit5->Text.c_str()), StringToInt(Edit6->Text.c_str()),
                 StringToInt(Edit7->Text.c_str()), StringToInt(Edit8->Text.c_str())};

And as far as I know, it's okay, I tested it with some ShowMessage()'s

Because you're passing your array to a funtion as a pointer. So when you use my macro you say sizeof a pointer ( always 4bytes on 32-bit machines ) divided by size of the first element ( also 4 bytes in this case, integer ) so the result is 1.

cauz I want this function to be portable to other programs that will eventually need a function like this one...

so I want it to guess the maximum and be said the minimum...

VV

As you're using BCB, & if you want deal with arrays of stuff, take a look at the TList class.

Why not use a vector of ints and call the size() member function to return how many elements it has.

Code:

#include <vector>
...
using namespace std;

vector<int> nums;

nums.push_back(5);
nums.push_back(6);
nums.push_back(7);

nums.size();  // returns 3

Thanks all of you, I'll try these solution sunday evening or monday... I'll tell you about it!

thx again

VV
[email protected]

TCHAR *pszString;

// Assume you've assigned it to something

for (int i = 0; *(pszString + i * sizeof (TCHAR)) !=' \0'; i++);

// i is now the number of elements

/*
Unicode, here I come! Unicode is a two byte character designed for international compatability. TCHAR represents a character data type, if you define "UNICODE" before you include windows.h, TCHAR will be a two byte character, otherwise a standard char. Sooooo, we've got our pointer, pszString (hungarian notation for "pointer to a string terminated with a zero, String"), and theoretically assigned it to an array. Now, we get a for loop ready, and in the condition block, put into English(kinda):

terminate if the value of (pszString plus (the size of the character times the number of elements so far)) is the null character :þ.

*/