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Add virRandom() API to generate numbers with non-power-of-2 limit
The current virRandomBits() API is only usable if the caller wants a random number in the range [0, n-1) where n is a power of two. This adds a virRandom() API which generates a double in the range [0.0,1.0) with 48 bits of entropy. It then also adds a virRandomInt(uint32_t max) API which generates an unsigned in the range [0,@max) Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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@ -1641,8 +1641,10 @@ virPidFileDeletePath;
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# virrandom.h
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virRandom;
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virRandomBits;
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virRandomGenerateWWN;
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virRandomInt;
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# virsocketaddr.h
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@ -23,6 +23,7 @@
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#include <stdlib.h>
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#include <inttypes.h>
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#include <math.h>
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#include "virrandom.h"
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#include "threads.h"
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@ -108,6 +109,37 @@ uint64_t virRandomBits(int nbits)
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return ret;
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}
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/**
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* virRandom:
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*
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* Generate an evenly distributed random number between [0.0,1.0)
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*
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* Return: a random number with 48 bits of entropy
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*/
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double virRandom(void)
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{
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uint64_t val = virRandomBits(48);
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return ldexp(val, -48);
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}
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/**
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* virRandomInt:
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* @max: upper limit
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*
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* Generate an evenly distributed random integer between [0, @max)
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*
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* Return: a random number between [0,@max)
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*/
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uint32_t virRandomInt(uint32_t max)
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{
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double val = virRandom();
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return val * max;
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}
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#define QUMRANET_OUI "001a4a"
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#define VMWARE_OUI "000569"
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#define MICROSOFT_OUI "0050f2"
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@ -25,6 +25,8 @@
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# include "internal.h"
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uint64_t virRandomBits(int nbits);
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double virRandom(void);
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uint32_t virRandomInt(uint32_t max);
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int virRandomGenerateWWN(char **wwn, const char *virt_type);
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#endif /* __VIR_RANDOM_H__ */
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