The Tor Browser: nsprpub/pr/include/prrng.h@925c144e1f1f

     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/. */

     7 /*

     8 ** prrng.h -- NSPR Random Number Generator

     9 **

    10 **

    11 ** lth. 29-Oct-1999.

    12 */

    14 #ifndef prrng_h___

    15 #define prrng_h___

    17 #include "prtypes.h"

    19 PR_BEGIN_EXTERN_C

    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 );

    72 PR_END_EXTERN_C

    74 #endif /* prrng_h___ */

    75 /* end prrng.h */

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