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prrng.h
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00001 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
00002 /* ***** BEGIN LICENSE BLOCK *****
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00011  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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00014  *
00015  * The Original Code is the Netscape Portable Runtime (NSPR).
00016  *
00017  * The Initial Developer of the Original Code is
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00019  * Portions created by the Initial Developer are Copyright (C) 1999-2000
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00024  * Alternatively, the contents of this file may be used under the terms of
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00037 
00038 
00039 /*
00040 ** prrng.h -- NSPR Random Number Generator
00041 ** 
00042 **
00043 ** lth. 29-Oct-1999.
00044 */
00045 
00046 #ifndef prrng_h___ 
00047 #define prrng_h___
00048 
00049 #include "prtypes.h"
00050 
00051 PR_BEGIN_EXTERN_C
00052 
00053 /*
00054 ** PR_GetRandomNoise() -- Get random noise from the host platform
00055 **
00056 ** Description:
00057 ** PR_GetRandomNoise() provides, depending on platform, a random value.
00058 ** The length of the random value is dependent on platform and the
00059 ** platform's ability to provide a random value at that moment.
00060 **
00061 ** The intent of PR_GetRandomNoise() is to provide a "seed" value for a
00062 ** another random number generator that may be suitable for
00063 ** cryptographic operations. This implies that the random value
00064 ** provided may not be, by itself, cryptographically secure. The value
00065 ** generated by PR_GetRandomNoise() is at best, extremely difficult to
00066 ** predict and is as non-deterministic as the underlying platfrom can
00067 ** provide.
00068 **
00069 ** Inputs:
00070 **   buf -- pointer to a caller supplied buffer to contain the
00071 **          generated random number. buf must be at least as large as
00072 **          is specified in the 'size' argument.
00073 **
00074 **   size -- the requested size of the generated random number
00075 **
00076 ** Outputs:
00077 **   a random number provided in 'buf'.
00078 **
00079 ** Returns:
00080 **   PRSize value equal to the size of the random number actually
00081 **   generated, or zero. The generated size may be less than the size
00082 **   requested. A return value of zero means that PR_GetRandomNoise() is
00083 **   not implemented on this platform, or there is no available noise
00084 **   available to be returned at the time of the call.
00085 **
00086 ** Restrictions:
00087 **   Calls to PR_GetRandomNoise() may use a lot of CPU on some platforms.
00088 **   Some platforms may block for up to a few seconds while they
00089 **   accumulate some noise. Busy machines generate lots of noise, but
00090 **   care is advised when using PR_GetRandomNoise() frequently in your
00091 **   application.
00092 **
00093 ** History:
00094 **   Parts of the model dependent implementation for PR_GetRandomNoise()
00095 **   were taken in whole or part from code previously in Netscape's NSS
00096 **   component.
00097 **
00098 */
00099 NSPR_API(PRSize) PR_GetRandomNoise( 
00100     void    *buf,
00101     PRSize  size
00102 );
00103 
00104 PR_END_EXTERN_C
00105 
00106 #endif /* prrng_h___ */
00107 /* end prrng.h */