pre-allocate memory for string

Hello all,
is there a way to pre-allocate memory for a string?

so if I want to do something like this:

Code:

---

char *data;
string value;

for (i=0; i<size; i++)
{
  value += data[i];
}

---

And I wanted to pre-allocate some memory this I could do:

Code:

---

string value[size];

---

I'm not looking for an array, but just a string. Set to the right size before I start loading it for speed.

Thanks,
Michael

It would be:

Code:

---

string value(size);

---

However, looking at the context, data presumably points somewhere. As such, instead of the loop, you can just write:

Code:

---

string value(data, data + size);

---

and get on with something more important.

Quote:

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Originally Posted by laserlight

It would be:

Code:

---

string value(size);

---

However, looking at the context, data presumably points somewhere. As such, instead of the loop, you can just write:

Code:

---

string value(data, data + size);

---

and get on with something more important.

---

Everyone yelled at me when I put that. They are arguing over if I'm putting a pointer in the size section or a very large number.

Why not just put

Code:

---

string value(data, size)

---

?

Thanks.

Quote:

---

Originally Posted by TheBigOnion

Everyone yelled at me when I put that. They are arguing over if I'm putting a pointer in the size section or a very large number.

---

If they object on those grounds, then they have no clue about pointer arithmetic, or they are simply unaware that std::string has a constructor that takes two iterators that denote a range.

Quote:

---

Originally Posted by TheBigOnion

Why not just put

Code:

---

string value(data, size)

---

?

---

That is certainly another option.

Quote:

---

Originally Posted by laserlight

If they object on those grounds, then they have no clue about pointer arithmetic, or they are simply unaware that std::string has a constructor that takes two iterators that denote a range.


That is certainly another option.

---

Then should it have been:

Code:

---

string value(data, data, size);

---

?

No, that would simply be wrong as there is no such constructor. (The third argument to these constructors is an allocator object, but the default is used if it is not provided.)

Basically, the iterator version is string(start, end) where start and end are two addresses (or objects acting as addresses) which forms a range from where to copy the data into the string. As such, your 3 argument constructor makes no sense.