mirror of
https://gitlab.com/ryandwyer/perfect-dark
synced 2026-06-05 11:17:23 -04:00
Ryan Dwyer
42 lines
875 B
C
42 lines
875 B
C
#include <ultra64.h>
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#include "constants.h"
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#include "bss.h"
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#include "lib/rng.h"
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#include "data.h"
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#include "types.h"
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u64 g_RngSeed = 0xab8d9f7781280783;
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/**
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* Generate a random number between 0 and 4294967295.
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*/
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u32 random(void)
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{
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g_RngSeed = ((g_RngSeed << 63) >> 31 | (g_RngSeed << 31) >> 32) ^ (g_RngSeed << 44) >> 32;
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g_RngSeed = ((g_RngSeed >> 20) & 0xfff) ^ g_RngSeed;
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return g_RngSeed;
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}
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/**
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* Set the given seed as the RNG seed. Add 1 to make sure it isn't 0.
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*/
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void rngSetSeed(u64 seed)
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{
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g_RngSeed = seed + 1;
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}
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/**
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* Rotate the given seed using the same algorithm as random().
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*
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* Store the new 64-bit seed at the pointed address and return the same seed
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* cast as a u32.
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*/
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u32 rngRotateSeed(u64 *seed)
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{
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*seed = ((*seed << 63) >> 31 | (*seed << 31) >> 32) ^ (*seed << 44) >> 32;
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*seed = ((*seed >> 20) & 0xfff) ^ *seed;
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return *seed;
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}
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