nsprpub/pr/include/prrng.h

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6
   7 /*
   8 ** prrng.h -- NSPR Random Number Generator
   9 **
  10 **
  11 ** lth. 29-Oct-1999.
  12 */
  13
  14 #ifndef prrng_h___
  15 #define prrng_h___
  16
  17 #include "prtypes.h"
  18
  19 PR_BEGIN_EXTERN_C
  20
  21 /*
  22 ** PR_GetRandomNoise() -- Get random noise from the host platform
  23 **
  24 ** Description:
  25 ** PR_GetRandomNoise() provides, depending on platform, a random value.
  26 ** The length of the random value is dependent on platform and the
  27 ** platform's ability to provide a random value at that moment.
  28 **
  29 ** The intent of PR_GetRandomNoise() is to provide a "seed" value for a
  30 ** another random number generator that may be suitable for
  31 ** cryptographic operations. This implies that the random value
  32 ** provided may not be, by itself, cryptographically secure. The value
  33 ** generated by PR_GetRandomNoise() is at best, extremely difficult to
  34 ** predict and is as non-deterministic as the underlying platfrom can
  35 ** provide.
  36 **
  37 ** Inputs:
  38 **   buf -- pointer to a caller supplied buffer to contain the
  39 **          generated random number. buf must be at least as large as
  40 **          is specified in the 'size' argument.
  41 **
  42 **   size -- the requested size of the generated random number
  43 **
  44 ** Outputs:
  45 **   a random number provided in 'buf'.
  46 **
  47 ** Returns:
  48 **   PRSize value equal to the size of the random number actually
  49 **   generated, or zero. The generated size may be less than the size
  50 **   requested. A return value of zero means that PR_GetRandomNoise() is
  51 **   not implemented on this platform, or there is no available noise
  52 **   available to be returned at the time of the call.
  53 **
  54 ** Restrictions:
  55 **   Calls to PR_GetRandomNoise() may use a lot of CPU on some platforms.
  56 **   Some platforms may block for up to a few seconds while they
  57 **   accumulate some noise. Busy machines generate lots of noise, but
  58 **   care is advised when using PR_GetRandomNoise() frequently in your
  59 **   application.
  60 **
  61 ** History:
  62 **   Parts of the model dependent implementation for PR_GetRandomNoise()
  63 **   were taken in whole or part from code previously in Netscape's NSS
  64 **   component.
  65 **
  66 */
  67 NSPR_API(PRSize) PR_GetRandomNoise(
  68     void    *buf,
  69     PRSize  size
  70 );
  71
  72 PR_END_EXTERN_C
  73
  74 #endif /* prrng_h___ */
  75 /* end prrng.h */