randparkmiller.cpp revision e64031e20c39650a7bc902a3e1aba613b9415dee
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * IPRT - Random Numbers, Park-Miller Pseudo Random.
e64031e20c39650a7bc902a3e1aba613b9415deevboxsync * Copyright (C) 2008 Oracle Corporation
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6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync/*******************************************************************************
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync* Header Files *
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync*******************************************************************************/
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsyncDECLINLINE(uint32_t) rtRandParkMillerU31(uint32_t *pu32Ctx)
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * Park-Miller random number generator:
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * X2 = X1 * g mod n.
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * We use the constants suggested by Park and Miller:
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * n = 2^31 - 1 = INT32_MAX
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * g = 7^5 = 16807
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * This will produce numbers in the range [0..INT32_MAX-1], which is
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * almost 31-bits. We'll ignore the missing number for now and settle
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * for just filling in the missing bit instead (the caller does this).
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync /*uint32_t x2 = ((uint64_t)x1 * 16807) % INT32_MAX;*/
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync uint32_t x2 = ASMModU64ByU32RetU32(ASMMult2xU32RetU64(x1, 16807), INT32_MAX);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync/** @copydoc RTRANDINT::pfnGetU32 */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsyncstatic DECLCALLBACK(uint32_t) rtRandParkMillerGetU32(PRTRANDINT pThis, uint32_t u32First, uint32_t u32Last)
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync /* 30 + 2 bit (make up for the missing INT32_MAX value) */
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync off = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync pThis->u.ParkMiller.u32Bits = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync /* The exact range. */
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync off = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync /* Requested 23 or fewer bits, just lose the lower bit. */
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync off = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync * 30 + 6 bits.
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync uint64_t off64 = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync pThis->u.ParkMiller.u32Bits = rtRandParkMillerU31(&pThis->u.ParkMiller.u32Ctx);
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync off64 |= (uint64_t)(pThis->u.ParkMiller.u32Bits & 0x3f) << 30;
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync/** @copydoc RTRANDINT::pfnSeed */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsyncstatic DECLCALLBACK(int) rtRandParkMillerSeed(PRTRANDINT pThis, uint64_t u64Seed)
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync/** @copydoc RTRANDINT::pfnSaveState */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsyncstatic DECLCALLBACK(int) rtRandParkMillerSaveState(PRTRANDINT pThis, char *pszState, size_t *pcbState)
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync#define RTRAND_PARKMILLER_STATE_SIZE (3+8+1+8+1+2+1+1)
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync RTStrPrintf(pszState, *pcbState, "PM:%08RX32,%08RX32,%02x;",
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync/** @copydoc RTRANDINT::pfnRestoreState */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsyncstatic DECLCALLBACK(int) rtRandParkMillerRestoreState(PRTRANDINT pThis, char const *pszState)
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync /* marker */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync /* u32Ctx */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync int rc = RTStrToUInt32Ex(pszState, &pszNext, 16, &u32Ctx);
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync /* u32Bits */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync rc = RTStrToUInt32Ex(pszState, &pszNext, 16, &u32Bits);
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync /* cBits */
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync rc = RTStrToUInt32Ex(pszState, &pszNext, 16, &cBits);
062b8a43e237d9e2edde03b5837d44506e35eb47vboxsync /* commit */
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsyncRTDECL(int) RTRandAdvCreateParkMiller(PRTRAND phRand) RT_NO_THROW
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync PRTRANDINT pThis = (PRTRANDINT)RTMemAlloc(sizeof(*pThis));
6fea4abcc6ee0f2797ac01ef79c374d506aedc02vboxsync pThis->pfnGetBytes= rtRandAdvSynthesizeBytesFromU32;