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88 lines
2.1 KiB
C++
88 lines
2.1 KiB
C++
/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
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// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
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#ident "$Id$"
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#ident "Copyright (c) 2007-2012 Tokutek Inc. All rights reserved."
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#ifndef TOKU_RANDOM_H
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#define TOKU_RANDOM_H
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#include <config.h>
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#include <toku_portability.h>
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#include <toku_assert.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <limits.h>
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#if defined(HAVE_RANDOM_R)
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// Definition of randu62 and randu64 assume myrandom_r generates 31 low-order bits
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static_assert(RAND_MAX == INT32_MAX, "Unexpected RAND_MAX");
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static inline int
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myinitstate_r(unsigned int seed, char *statebuf, size_t statelen, struct random_data *buf)
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{
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return initstate_r(seed, statebuf, statelen, buf);
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}
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static inline int32_t
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myrandom_r(struct random_data *buf)
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{
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int32_t x;
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int r = random_r(buf, &x);
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lazy_assert_zero(r);
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return x;
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}
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#elif defined(HAVE_NRAND48)
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struct random_data {
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unsigned short xsubi[3];
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};
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static inline int
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myinitstate_r(unsigned int seed, char *UU(statebuf), size_t UU(statelen), struct random_data *buf)
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{
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buf->xsubi[0] = (seed & 0xffff0000) >> 16;
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buf->xsubi[0] = (seed & 0x0000ffff);
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buf->xsubi[2] = (seed & 0x00ffff00) >> 8;
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return 0;
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}
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static inline int32_t
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myrandom_r(struct random_data *buf)
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{
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int32_t x = nrand48(buf->xsubi);
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return x;
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}
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#else
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# error "no suitable reentrant random function available (checked random_r and nrand48)"
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#endif
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static inline uint64_t
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randu62(struct random_data *buf)
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{
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uint64_t a = myrandom_r(buf);
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uint64_t b = myrandom_r(buf);
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return (a | (b << 31));
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}
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static inline uint64_t
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randu64(struct random_data *buf)
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{
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uint64_t r62 = randu62(buf);
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uint64_t c = myrandom_r(buf);
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return (r62 | ((c & 0x3) << 62));
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}
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static inline uint32_t
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rand_choices(struct random_data *buf, uint32_t choices) {
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invariant(choices >= 2);
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invariant(choices < INT32_MAX);
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uint32_t bits = 2;
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while (bits < choices) {
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bits *= 2;
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}
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--bits;
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uint32_t result;
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do {
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result = myrandom_r(buf) & bits;
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} while (result >= choices);
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return result;
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}
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#endif // TOKU_RANDOM_H
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