Upper Bound and Lower Bound of an array [SOLVED]

[Andrew Brock]

Since it is C++, why not make your own little class that stores the length of the array.

class Buffer {
public:
Buffer(unsigned nSize) : m_pBuffer(NULL), m_nLength(nSize) {
if (nSize > 0) {
m_pBuffer = new BYTE[nSize];
if (m_pBuffer == NULL) {
m_nLength = 0;
//you ran out of memory, do something
}
}
}
~Buffer() {
if (m_pBuffer != NULL) {
delete []m_pBuffer;
}
}
unsigned GetLength() {
return m_nLength;
}
BYTE &operator[](unsigned nIndex) {
if (nIndex >= m_nLength) {
//error somehow
}
return m_pBuffer[nIndex];
}
BYTE *operator*() {
return m_pBuffer;
}

private:
	BYTE \*m\_pBuffer;
	unsigned nLength;

};

Then you can use it like

Buffer bufData(64);
strcpy(*bufData, "hello world"); //the operator*() can be used to get a pointer to the data
//print the length
printf("The valid range is 0-%u\n", bufData.GetLength() - 1); //remember indices start at 0 and go to n-1
printf("The 2nd character is \'%c\'\n", bufData[1]); //Again, indices start at 0 making the 2nd element index 1
//The buffer automatically cleans up its memory when it goes out of scope

You still need to call delete pData; if the buffer was created with Buffer pData = new Buffer(64);

[goldenrose9]

yes, 0 to 63, but i was in search of a function that returns the bound of an array, as in vb UBound() and LBound() function is used. Is there any similer function that helps to acheive bounds in c++

Some Day I Will Prove MySelf :: GOLD

[Cool_Dev]

Nope. :) Otherwise you have to go for STL container classes in C++, collection classes in MFC, or your own array class to achieve this.

[Hans Dietrich]

VS provides the macro

#define _countof(array) (sizeof(array)/sizeof(array[0]))

[Note: this can't be used for arrays allocated via new.]

Best wishes, Hans

---

[Hans Dietrich Software]

[Niklas L]

Problem is, when you write things like this yourself, you always forget something :) . Like declaring GetLength() const for instance, and having a const accessor. std::vector<BYTE> is the way to go.

home

[Stefan_Lang]

pByte as you declared is just a pointer. You are putting the semantics of an array into it by assigning the memory for it. But the compiler has no way of knowing what, exactly this pointer is pointing to at any time. In other words, no, the compiler cannot know what the semantics of the memory is that any pointer is pointing to, nor can any function. That said, the above is not entirely true: when you compile your program in debug mode and check what new (and delete) actually do, you will find that, internally, the system's memory manager indeed does store information about the memory being allocated, including the information whether this memory is for an array of objects or just one object. Therefore, if you try to release an array using delete rather than delete [], you will get a runtime error! If you want to, you can replace the system's operator new and delete with your own implementations. These could then store additional information, such as the number of elements being allocated, and then you could implement a function UBound() that takes advantage of that hidden information.

[goldenrose9]

thanx.:thumbsup:

Some Day I Will Prove MySelf :: GOLD

[Niklas L]

hmm, never thought of that. Rather clever!

home

[David Crow]

Stefan63 wrote:

If you want to, you can replace the system's operator new and delete with your own implementations. These could then store additional information, such as the number of elements being allocated...

Which is essentially what happens in debug mode.

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[Lost User]

goldenrose9 wrote:

how to get the upper bound and lower bound of an array BYTE *pByte = new BYTE[64];

In C/C++ there is nothing like lower bound of array is zero. Upper bound is 63 as you specified 64 (bcoz array starts with zero so 64-1).