source: vbox/trunk/src/libs/xpcom18a4/nsprpub/pr/include/prrng.h@ 1

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the Netscape Portable Runtime (NSPR).
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1999-2000
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */


/*
** prrng.h -- NSPR Random Number Generator
** 
**
** lth. 29-Oct-1999.
*/

#ifndef prrng_h___ 
#define prrng_h___

#include "prtypes.h"

PR_BEGIN_EXTERN_C

/*
** PR_GetRandomNoise() -- Get random noise from the host platform
**
** Description:
** PR_GetRandomNoise() provides, depending on platform, a random value.
** The length of the random value is dependent on platform and the
** platform's ability to provide a random value at that moment.
**
** The intent of PR_GetRandomNoise() is to provide a "seed" value for a
** another random number generator that may be suitable for
** cryptographic operations. This implies that the random value
** provided may not be, by itself, cryptographically secure. The value
** generated by PR_GetRandomNoise() is at best, extremely difficult to
** predict and is as non-deterministic as the underlying platfrom can
** provide.
**
** Inputs:
**   buf -- pointer to a caller supplied buffer to contain the
**          generated random number. buf must be at least as large as
**          is specified in the 'size' argument.
**
**   size -- the requested size of the generated random number
**
** Outputs:
**   a random number provided in 'buf'.
**
** Returns:
**   PRSize value equal to the size of the random number actually
**   generated, or zero. The generated size may be less than the size
**   requested. A return value of zero means that PR_GetRandomNoise() is
**   not implemented on this platform, or there is no available noise
**   available to be returned at the time of the call.
**
** Restrictions:
**   Calls to PR_GetRandomNoise() may use a lot of CPU on some platforms.
**   Some platforms may block for up to a few seconds while they
**   accumulate some noise. Busy machines generate lots of noise, but
**   care is advised when using PR_GetRandomNoise() frequently in your
**   application.
**
** History:
**   Parts of the model dependent implementation for PR_GetRandomNoise()
**   were taken in whole or part from code previously in Netscape's NSS
**   component.
**
*/
NSPR_API(PRSize) PR_GetRandomNoise( 
    void    *buf,
    PRSize  size
);

PR_END_EXTERN_C

#endif /* prrng_h___ */
/* end prrng.h */