mirror of
https://github.com/openvswitch/ovs
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2737b46d87
random_range, random_uint8 and random_uint16 are basically just wrappers around random_uint32. Hence, don't export these functions so the compiler can be smarter when it comes to optimizations. Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com> Signed-off-by: Ben Pfaff <blp@nicira.com>
120 lines
2.6 KiB
C
120 lines
2.6 KiB
C
/*
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* Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <config.h>
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#include "random.h"
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#include <errno.h>
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#include <stdlib.h>
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#include <sys/time.h>
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#include "entropy.h"
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#include "hash.h"
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#include "ovs-thread.h"
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#include "timeval.h"
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#include "util.h"
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/* This is the 32-bit PRNG recommended in G. Marsaglia, "Xorshift RNGs",
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* _Journal of Statistical Software_ 8:14 (July 2003). According to the paper,
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* it has a period of 2**32 - 1 and passes almost all tests of randomness.
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*
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* We use this PRNG instead of libc's rand() because rand() varies in quality
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* and because its maximum value also varies between 32767 and INT_MAX, whereas
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* we often want random numbers in the full range of uint32_t.
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*
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* This random number generator is intended for purposes that do not require
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* cryptographic-quality randomness. */
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/* Current random state. */
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DEFINE_STATIC_PER_THREAD_DATA(uint32_t, seed, 0);
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static uint32_t random_next(void);
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void
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random_init(void)
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{
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uint32_t *seedp = seed_get();
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while (!*seedp) {
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struct timeval tv;
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uint32_t entropy;
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pthread_t self;
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xgettimeofday(&tv);
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get_entropy_or_die(&entropy, 4);
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self = pthread_self();
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*seedp = (tv.tv_sec ^ tv.tv_usec ^ entropy
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^ hash_bytes(&self, sizeof self, 0));
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}
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}
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void
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random_set_seed(uint32_t seed_)
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{
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ovs_assert(seed_);
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*seed_get() = seed_;
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}
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void
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random_bytes(void *p_, size_t n)
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{
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uint8_t *p = p_;
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random_init();
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for (; n > 4; p += 4, n -= 4) {
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uint32_t x = random_next();
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memcpy(p, &x, 4);
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}
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if (n) {
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uint32_t x = random_next();
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memcpy(p, &x, n);
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}
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}
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uint32_t
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random_uint32(void)
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{
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random_init();
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return random_next();
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}
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uint64_t
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random_uint64(void)
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{
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uint64_t x;
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random_init();
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x = random_next();
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x |= (uint64_t) random_next() << 32;
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return x;
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}
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static uint32_t
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random_next(void)
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{
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uint32_t *seedp = seed_get_unsafe();
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*seedp ^= *seedp << 13;
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*seedp ^= *seedp >> 17;
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*seedp ^= *seedp << 5;
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return *seedp;
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}
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