| 1 | /* $Id: randparkmiller.cpp 69111 2017-10-17 14:26:02Z vboxsync $ */
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| 2 | /** @file
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| 3 | * IPRT - Random Numbers, Park-Miller Pseudo Random.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2008-2017 Oracle Corporation
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| 8 | *
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| 9 | * This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | * available from http://www.virtualbox.org. This file is free software;
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| 11 | * you can redistribute it and/or modify it under the terms of the GNU
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| 12 | * General Public License (GPL) as published by the Free Software
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| 13 | * Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | *
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| 17 | * The contents of this file may alternatively be used under the terms
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| 18 | * of the Common Development and Distribution License Version 1.0
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| 19 | * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | * VirtualBox OSE distribution, in which case the provisions of the
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| 21 | * CDDL are applicable instead of those of the GPL.
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| 22 | *
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| 23 | * You may elect to license modified versions of this file under the
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| 24 | * terms and conditions of either the GPL or the CDDL or both.
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| 25 | */
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| 26 |
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| 27 |
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| 28 | /*********************************************************************************************************************************
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| 29 | * Header Files *
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| 30 | *********************************************************************************************************************************/
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| 31 | #include <iprt/rand.h>
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| 32 | #include "internal/iprt.h"
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| 33 |
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| 34 | #include <iprt/asm-math.h>
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| 35 | #include <iprt/mem.h>
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| 36 | #include <iprt/string.h>
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| 37 | #include <iprt/err.h>
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| 38 | #include "internal/rand.h"
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| 39 | #include "internal/magics.h"
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| 40 |
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| 41 |
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| 42 |
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| 43 | DECLINLINE(uint32_t) rtRandParkMillerU31(uint32_t *pu32Ctx)
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| 44 | {
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| 45 | /*
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| 46 | * Park-Miller random number generator:
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| 47 | * X2 = X1 * g mod n.
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| 48 | *
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| 49 | * We use the constants suggested by Park and Miller:
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| 50 | * n = 2^31 - 1 = INT32_MAX
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| 51 | * g = 7^5 = 16807
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| 52 | *
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| 53 | * This will produce numbers in the range [0..INT32_MAX-1], which is
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| 54 | * almost 31-bits. We'll ignore the missing number for now and settle
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| 55 | * for just filling in the missing bit instead (the caller does this).
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| 56 | */
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| 57 | uint32_t x1 = *pu32Ctx;
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| 58 | if (!x1)
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| 59 | x1 = 20080806;
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| 60 | /*uint32_t x2 = ((uint64_t)x1 * 16807) % INT32_MAX;*/
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| 61 | uint32_t x2 = ASMModU64ByU32RetU32(ASMMult2xU32RetU64(x1, 16807), INT32_MAX);
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| 62 | return *pu32Ctx = x2;
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| 63 | }
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| 64 |
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| 65 |
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| 66 | /** @copydoc RTRANDINT::pfnGetU32 */
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| 67 | static DECLCALLBACK(uint32_t) rtRandParkMillerGetU32(PRTRANDINT pThis, uint32_t u32First, uint32_t u32Last)
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| 68 | {
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| 69 | uint32_t off;
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| 70 | uint32_t offLast = u32Last - u32First;
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| 71 | if (offLast == UINT32_MAX)
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| 72 | {
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| 73 | /* 30 + 2 bit (make up for the missing INT32_MAX value) */
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| 74 | off = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
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| 75 | if (pThis->u.ParkMiller.cBits < 2)
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| 76 | {
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| 77 | pThis->u.ParkMiller.u32Bits = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
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| 78 | pThis->u.ParkMiller.cBits = 30;
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| 79 | }
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| 80 | off >>= 1;
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| 81 | off |= (pThis->u.ParkMiller.u32Bits & 3) << 30;
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| 82 | pThis->u.ParkMiller.u32Bits >>= 2;
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| 83 | pThis->u.ParkMiller.cBits -= 2;
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| 84 | }
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| 85 | else if (offLast == (uint32_t)INT32_MAX - 1)
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| 86 | /* The exact range. */
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| 87 | off = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
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| 88 | else if (offLast < UINT32_C(0x07ffffff))
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| 89 | {
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| 90 | /* Requested 23 or fewer bits, just lose the lower bit. */
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| 91 | off = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
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| 92 | off >>= 1;
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| 93 | off %= (offLast + 1);
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| 94 | }
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| 95 | else
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| 96 | {
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| 97 | /*
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| 98 | * 30 + 6 bits.
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| 99 | */
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| 100 | uint64_t off64 = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
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| 101 | if (pThis->u.ParkMiller.cBits < 6)
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| 102 | {
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| 103 | pThis->u.ParkMiller.u32Bits = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
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| 104 | pThis->u.ParkMiller.cBits = 30;
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| 105 | }
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| 106 | off64 >>= 1;
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| 107 | off64 |= (uint64_t)(pThis->u.ParkMiller.u32Bits & 0x3f) << 30;
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| 108 | pThis->u.ParkMiller.u32Bits >>= 6;
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| 109 | pThis->u.ParkMiller.cBits -= 6;
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| 110 | off = ASMModU64ByU32RetU32(off64, offLast + 1);
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| 111 | }
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| 112 | return off + u32First;
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| 113 | }
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| 114 |
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| 115 |
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| 116 | /** @copydoc RTRANDINT::pfnSeed */
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| 117 | static DECLCALLBACK(int) rtRandParkMillerSeed(PRTRANDINT pThis, uint64_t u64Seed)
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| 118 | {
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| 119 | pThis->u.ParkMiller.u32Ctx = (uint32_t)u64Seed;
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| 120 | pThis->u.ParkMiller.u32Bits = 0;
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| 121 | pThis->u.ParkMiller.cBits = 0;
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| 122 | return VINF_SUCCESS;
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| 123 | }
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| 124 |
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| 125 |
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| 126 | /** @copydoc RTRANDINT::pfnSaveState */
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| 127 | static DECLCALLBACK(int) rtRandParkMillerSaveState(PRTRANDINT pThis, char *pszState, size_t *pcbState)
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| 128 | {
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| 129 | #define RTRAND_PARKMILLER_STATE_SIZE (3+8+1+8+1+2+1+1)
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| 130 |
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| 131 | if (*pcbState < RTRAND_PARKMILLER_STATE_SIZE)
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| 132 | {
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| 133 | *pcbState = RTRAND_PARKMILLER_STATE_SIZE;
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| 134 | return VERR_BUFFER_OVERFLOW;
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| 135 | }
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| 136 | RTStrPrintf(pszState, *pcbState, "PM:%08RX32,%08RX32,%02x;",
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| 137 | pThis->u.ParkMiller.u32Ctx,
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| 138 | pThis->u.ParkMiller.u32Bits,
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| 139 | pThis->u.ParkMiller.cBits);
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| 140 | return VINF_SUCCESS;
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| 141 | }
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| 142 |
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| 143 |
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| 144 | /** @copydoc RTRANDINT::pfnRestoreState */
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| 145 | static DECLCALLBACK(int) rtRandParkMillerRestoreState(PRTRANDINT pThis, char const *pszState)
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| 146 | {
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| 147 | /* marker */
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| 148 | if ( pszState[0] != 'P'
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| 149 | || pszState[1] != 'M'
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| 150 | || pszState[2] != ':')
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| 151 | return VERR_PARSE_ERROR;
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| 152 | pszState += 3;
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| 153 |
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| 154 | /* u32Ctx */
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| 155 | char *pszNext = NULL;
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| 156 | uint32_t u32Ctx;
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| 157 | int rc = RTStrToUInt32Ex(pszState, &pszNext, 16, &u32Ctx);
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| 158 | if ( rc != VWRN_TRAILING_CHARS
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| 159 | || pszNext != pszState + 8
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| 160 | || *pszNext != ',')
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| 161 | return VERR_PARSE_ERROR;
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| 162 | pszState += 8 + 1;
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| 163 |
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| 164 | /* u32Bits */
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| 165 | uint32_t u32Bits;
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| 166 | rc = RTStrToUInt32Ex(pszState, &pszNext, 16, &u32Bits);
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| 167 | if ( rc != VWRN_TRAILING_CHARS
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| 168 | || pszNext != pszState + 8
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| 169 | || *pszNext != ',')
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| 170 | return VERR_PARSE_ERROR;
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| 171 | pszState += 8 + 1;
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| 172 |
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| 173 | /* cBits */
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| 174 | uint32_t cBits;
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| 175 | rc = RTStrToUInt32Ex(pszState, &pszNext, 16, &cBits);
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| 176 | if ( rc != VWRN_TRAILING_CHARS
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| 177 | || pszNext != pszState + 2
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| 178 | || *pszNext != ';'
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| 179 | || pszNext[1] != '\0')
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| 180 | return VERR_PARSE_ERROR;
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| 181 |
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| 182 | /* commit */
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| 183 | pThis->u.ParkMiller.u32Ctx = u32Ctx;
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| 184 | pThis->u.ParkMiller.u32Bits = u32Bits;
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| 185 | pThis->u.ParkMiller.cBits = cBits;
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| 186 | return VINF_SUCCESS;
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| 187 | }
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| 188 |
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| 189 |
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| 190 | RTDECL(int) RTRandAdvCreateParkMiller(PRTRAND phRand) RT_NO_THROW_DEF
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| 191 | {
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| 192 | PRTRANDINT pThis = (PRTRANDINT)RTMemAlloc(sizeof(*pThis));
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| 193 | if (!pThis)
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| 194 | return VERR_NO_MEMORY;
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| 195 | pThis->u32Magic = RTRANDINT_MAGIC;
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| 196 | pThis->pfnGetBytes= rtRandAdvSynthesizeBytesFromU32;
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| 197 | pThis->pfnGetU32 = rtRandParkMillerGetU32;
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| 198 | pThis->pfnGetU64 = rtRandAdvSynthesizeU64FromU32;
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| 199 | pThis->pfnSeed = rtRandParkMillerSeed;
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| 200 | pThis->pfnSaveState = rtRandParkMillerSaveState;
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| 201 | pThis->pfnRestoreState = rtRandParkMillerRestoreState;
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| 202 | pThis->pfnDestroy = rtRandAdvDefaultDestroy;
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| 203 | pThis->u.ParkMiller.u32Ctx = 0x20080806;
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| 204 | pThis->u.ParkMiller.u32Bits = 0;
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| 205 | pThis->u.ParkMiller.cBits = 0;
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| 206 | *phRand = pThis;
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| 207 | return VINF_SUCCESS;
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| 208 | }
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| 209 | RT_EXPORT_SYMBOL(RTRandAdvCreateParkMiller);
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| 210 |
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