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02.23.2008 at 06:59AM PST, ID: 23187069
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7.8

How do you set minimum/maximum values when generating random numbers?

Asked by Visual_Pro in Microsoft Visual C++.Net, C++ Programming Language, Microsoft Visual C#.Net

Tags:

I just have a small question about a console-based random number generating program I've created which uses the CryptGenRandom function.  Basically the random numbers are generating fine but the minimum or maximum number it generates is well into the +/- billions.

Now I know the 2nd property of that function decides the size of the number and originally I was using sizeof(int) but after much effort in experimenting around I can't find a reliable way to make it generate random numbers within a given range that I set (e.g. from 1 to 100).

The best I've been able to do is use this line (full source is below):

if (!CryptGenRandom(Provider, sizeof(char), (unsigned char *) &RetValue))

which by using sizeof(char) is generating random numbers from 0 to 255 for me.  But I'd ideally like to be able to set that as low as 1 to 50.  So if you can give me any advice on what I can do to set a min/max range for the numbers that would be muchly appreciated.  Start Free Trial 
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#include "stdafx.h"
#include <windows.h>
#include <wincrypt.h>
#include <iostream>
 
#define _WIN32_WINNT 0x0400
 
using namespace std;
 
int __fastcall GenerateRndNum()
   {
   static HCRYPTPROV Provider = NULL;
   int RndNum;
    
   if (!Provider)
    {
    if (!CryptAcquireContext(&Provider, NULL, NULL, PROV_RSA_FULL, 0))
    if (!CryptAcquireContext(&Provider, NULL, NULL, PROV_RSA_FULL, CRYPT_NEWKEYSET))
    return(0);
    
    GenerateRndNum(); 
    }
 
   RndNum = 0;
   if (!CryptGenRandom(Provider, sizeof(char), (unsigned char *) &RndNum))
    RndNum = 0;
   return(RndNum);
   }
 
 
int _tmain(int argc, _TCHAR* argv[])
{
	cout << "Calculating..." << endl;
	
         for (i=0;i<50;i++)
	{
		cout << GenerateRndNum() << endl;
	}
 
		cout << "Calculating finished." << endl;
	
	return 0;
}
 
Keywords: How do you set minimum/maximum va…
Title
1 sizeof struct
2 sizeof
3 unsigned char
4 sizeof(*this)
5 Sizeof()
6 convert unsigned int to unsigned char
 
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[+][-]02.23.2008 at 07:06AM PST, ID: 20965168

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Zones: Microsoft Visual C++.Net, C++ Programming Language, Microsoft Visual C#.Net
Tags: Visual C++, Visual C#
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Solution Provided By: evilrix
Participating Experts: 3
Solution Grade: A
 
 
[+][-]02.23.2008 at 08:08AM PST, ID: 20965397

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[+][-]02.23.2008 at 09:42AM PST, ID: 20965778

At Experts Exchange, members can ask their questions to thousands of technology professionals, also known as Experts. Experts compete and collaborate to answer those questions by leaving comments like this one.

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