346 lines
8.1 KiB
C
346 lines
8.1 KiB
C
// BLANKART
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//-----------------------------------------------------------------------------
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// Copyright (C) 1993-1996 by id Software, Inc.
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// Copyright (C) 1998-2000 by DooM Legacy Team.
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// Copyright (C) 2012-2016 by Matthew "Kaito Sinclaire" Walsh.
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// Copyright (C) 1999-2020 by Sonic Team Junior.
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//
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// This program is free software distributed under the
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// terms of the GNU General Public License, version 2.
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// See the 'LICENSE' file for more details.
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//-----------------------------------------------------------------------------
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/// \file m_random.c
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/// \brief RNG for client effects and PRNG for game actions
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#include "doomdef.h"
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#include "doomtype.h"
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#include "k_stats.h" // kartstats.totalplaytime
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#include "m_random.h"
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#include "m_fixed.h"
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// ---------------------------
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// RNG functions (not synched)
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// ---------------------------
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ATTRINLINE static UINT32 FUNCINLINE __external_prng__(void)
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{
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UINT32 rnd = rand();
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#if RAND_MAX < 65535
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// Compensate for especially bad randomness.
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UINT32 rndv = (rand() & 1) << 15;
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rnd ^= rndv;
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#endif
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// Shuffle like we do for our own PRNG, since RAND_MAX
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// tends to be [0, INT32_MAX] instead of [0, UINT32_MAX].
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rnd ^= rnd >> 13;
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rnd ^= rnd >> 11;
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rnd ^= rnd << 21;
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return (rnd * 36548569);
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}
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ATTRINLINE static UINT32 FUNCINLINE __external_prng_bound__(UINT32 bound)
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{
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// Handle zero like it would previously.
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if (bound == 0)
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{
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(void)__external_prng__();
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return 0;
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}
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else
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{
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// Do rejection sampling to remove the modulo bias.
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UINT32 threshold = -bound % bound;
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for (;;)
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{
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UINT32 r = __external_prng__();
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if (r >= threshold)
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{
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return r % bound;
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}
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}
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}
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}
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/** Provides a random 32-bit number. Distribution is uniform.
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* As with all M_Random functions, not synched in netgames.
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*
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* \return A random 32-bit number.
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*/
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UINT32 M_Random(void)
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{
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return __external_prng__();
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}
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/** Provides a random fixed point number. Distribution is uniform.
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* As with all M_Random functions, not synched in netgames.
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*
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* \return A random fixed point number from [0,1).
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*/
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fixed_t M_RandomFixed(void)
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{
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return (fixed_t)(__external_prng_bound__(FRACUNIT));
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}
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/** Provides a random byte. Distribution is uniform.
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* As with all M_Random functions, not synched in netgames.
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*
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* \return A random integer from [0, 255].
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*/
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UINT8 M_RandomByte(void)
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{
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return (UINT8)(__external_prng_bound__(UINT8_MAX));
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}
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/** Provides a random integer for picking random elements from an array.
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* Distribution is uniform.
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* As with all M_Random functions, not synched in netgames.
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*
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* \param a Number of items in array.
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* \return A random integer from [0,a).
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*/
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UINT32 M_RandomKey(UINT32 a)
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{
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return __external_prng_bound__(a);
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}
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/** Provides a random integer in a given range.
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* Distribution is uniform.
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* As with all M_Random functions, not synched in netgames.
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*
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* \param a Lower bound.
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* \param b Upper bound.
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* \return A random integer from [a,b].
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*/
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INT32 M_RandomRange(INT32 a, INT32 b)
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{
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return (INT32)(__external_prng_bound__((b - a) + 1)) + a;
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}
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// ------------------------
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// PRNG functions (synched)
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// ------------------------
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// Holds the current seed.
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static UINT32 randomseed = 0xBADE4404;
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// Holds the INITIAL seed value. Used for demos, possibly other debugging.
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static UINT32 initialseed = 0xBADE4404;
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/** Provides a random 32 bit integer.
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* This is a variant of an xorshift PRNG; state fits in a 32 bit integer structure.
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*
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* \return A random, uniformly distributed number from [0,UINT32_MAX].
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*/
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ATTRINLINE static UINT32 FUNCINLINE __internal_prng__(void)
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{
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randomseed ^= randomseed >> 13;
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randomseed ^= randomseed >> 11;
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randomseed ^= randomseed << 21;
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return (randomseed*36548569);
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}
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/** Provides a random number within a specified range.
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*
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* \return A random, uniformly distributed number from [0,bound].
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*/
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ATTRINLINE static UINT32 FUNCINLINE __internal_prng_bound__(UINT32 bound)
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{
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// Handle zero like it would previously.
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if (bound == 0)
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{
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(void)__internal_prng__();
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return 0;
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}
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else
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{
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// Do rejection sampling to remove the modulo bias.
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UINT32 threshold = -bound % bound;
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for (;;)
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{
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UINT32 r = __internal_prng__();
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if (r >= threshold)
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{
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return r % bound;
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}
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}
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}
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}
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/** Provides a random fixed point number. Distribution is uniform.
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* Literally a wrapper for the internal PRNG function.
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*
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* \return A random fixed point number from [0,UINT32_MAX].
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*/
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#ifndef DEBUGRANDOM
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UINT32 P_Random(void)
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{
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#else
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UINT32 P_RandomD(const char *rfile, INT32 rline, pr_class_t pr_class)
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{
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CONS_Printf("P_Random(%u) at: %sp %d\n", pr_class, rfile, rline);
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#endif
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return __internal_prng__();
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}
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/** Provides a random fixed point number. Distribution is uniform.
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*
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* \return A random fixed point number from [0,1].
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*/
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#ifndef DEBUGRANDOM
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fixed_t P_RandomFixed(void)
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{
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#else
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fixed_t P_RandomFixedD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_RandomFixed() at: %sp %d\n", rfile, rline);
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#endif
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return (fixed_t)(__internal_prng_bound__(FRACUNIT));
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}
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/** Provides a random byte. Distribution is uniform.
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* If you're curious, (&0xFF00) >> 8 gives the same result
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* as a fixed point multiplication by 256.
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*
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* \return Random integer from [0,255].
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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UINT8 P_RandomByte(void)
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{
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#else
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UINT8 P_RandomByteD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_RandomByte() at: %sp %d\n", rfile, rline);
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#endif
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return (UINT8)(__internal_prng_bound__(UINT8_MAX));
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}
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/** Provides a random integer for picking random elements from an array.
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* Distribution is uniform.
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* NOTE: Maximum range is 65536.
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*
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* \param a Number of items in array.
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* \return A random integer from [0,a].
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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UINT32 P_RandomKey(UINT32 a)
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{
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#else
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UINT32 P_RandomKeyD(const char *rfile, INT32 rline, UINT32 a)
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{
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CONS_Printf("P_RandomKey() at: %sp %d\n", rfile, rline);
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#endif
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return __internal_prng_bound__(a);
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}
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/** Provides a random integer in a given range.
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* Distribution is uniform.
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* NOTE: Maximum range is 65536.
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*
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* \param a Lower bound.
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* \param b Upper bound.
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* \return A random integer from [a,b].
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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INT32 P_RandomRange(INT32 a, INT32 b)
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{
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#else
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INT32 P_RandomRangeD(const char *rfile, INT32 rline, INT32 a, INT32 b)
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{
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CONS_Printf("P_RandomRange() at: %sp %d\n", rfile, rline);
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#endif
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return (INT32)(__internal_prng_bound__((b - a) + 1)) + a;
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}
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// ----------------------
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// PRNG seeds & debugging
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// ----------------------
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/** Peeks to see what the next result from the PRNG will be.
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* Used for debugging.
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*
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* \return A 'random' number from [0,UINT32_MAX]
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* \sa __internal_prng__
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*/
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UINT32 P_RandomPeek(void)
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{
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UINT32 r = randomseed;
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UINT32 ret = __internal_prng__();
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randomseed = r;
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return ret;
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}
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/** Gets the current random seed. Used by netgame savegames.
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*
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* \return Current random seed.
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* \sa P_SetRandSeed
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*/
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#ifndef DEBUGRANDOM
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UINT32 P_GetRandSeed(void)
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{
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#else
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UINT32 P_GetRandSeedD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_GetRandSeed() at: %sp %d\n", rfile, rline);
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#endif
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return randomseed;
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}
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/** Gets the initial random seed. Used by demos.
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*
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* \return Initial random seed.
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* \sa P_SetRandSeed
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*/
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#ifndef DEBUGRANDOM
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UINT32 P_GetInitSeed(void)
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{
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#else
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UINT32 P_GetInitSeedD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_GetInitSeed() at: %sp %d\n", rfile, rline);
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#endif
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return initialseed;
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}
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/** Sets the random seed.
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* Used at the beginning of the game, and also for netgames.
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*
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* \param rindex New random index.
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* \sa P_GetRandSeed
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*/
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#ifndef DEBUGRANDOM
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void P_SetRandSeed(UINT32 seed)
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{
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#else
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void P_SetRandSeedD(const char *rfile, INT32 rline, UINT32 seed)
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{
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CONS_Printf("P_SetRandSeed() at: %sp %d\n", rfile, rline);
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#endif
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// xorshift requires a nonzero seed
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// this should never happen, but just in case it DOES, we check
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if (!seed) seed = 0xBADE4404;
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randomseed = initialseed = seed;
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}
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/** Gets a randomized seed for setting the random seed.
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*
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* \sa P_GetRandSeed
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*/
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UINT32 M_RandomizedSeed(void)
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{
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return ((kartstats.totalplaytime & 0xFFFF) << 16)|M_RandomFixed();
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}
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