79 lines
2.3 KiB
C
79 lines
2.3 KiB
C
#include "rand.h"
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#include "ch32fun.h"
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#include <stdint.h>
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#define BUILD_SEED \
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((uint64_t)(__TIME__[0]) * (uint64_t)(__TIME__[1]) * \
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(uint64_t)(__TIME__[3]) * (uint64_t)(__TIME__[4]) * \
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(uint64_t)(__TIME__[6]) * (uint64_t)(__TIME__[7]))
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#define FLASH_SEED_ADDR ((uintptr_t *)0x08003700) // PRNG state storage
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#define PRNG_SAVE_INTERVAL 50 // Save every 1000 calls to prand()
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static uint64_t seed = BUILD_SEED;
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// Initialize this to something close to interval
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static int prand_counter = PRNG_SAVE_INTERVAL - 10;
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uint64_t prand() {
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seed = seed * 6364136223846793005ULL + 1;
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if (++prand_counter >= PRNG_SAVE_INTERVAL) {
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rand_save_to_flash();
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prand_counter = 0;
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}
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return seed;
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}
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uint64_t prand_range(uint64_t min, uint64_t max) {
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return min + (prand() % (max - min + 1));
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}
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void sprand(uint64_t s) {
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if (s) {
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seed = s;
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} else {
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rand_reseed();
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}
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}
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void rand_reseed() {
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uint64_t stored_seed = *(volatile uint64_t *)FLASH_SEED_ADDR;
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if (stored_seed == 0 || stored_seed == 0xFFFFFFFFFFFFFFFFULL) {
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seed = BUILD_SEED;
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} else {
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seed = stored_seed;
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}
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}
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// See:
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// https://github.com/cnlohr/ch32v003fun/blob/2ac62072272f2ccd2122e688a9e0566de3976a94/examples/flashtest/flashtest.c
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void rand_save_to_flash() {
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FLASH->KEYR = 0x45670123; // Unlock flash
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FLASH->KEYR = 0xCDEF89AB;
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FLASH->MODEKEYR = 0x45670123; // Unlock programming mode
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FLASH->MODEKEYR = 0xCDEF89AB;
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// Erase the flash page
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FLASH->CTLR = CR_PAGE_ER;
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FLASH->ADDR = (intptr_t)FLASH_SEED_ADDR;
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FLASH->CTLR = CR_STRT_Set | CR_PAGE_ER;
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while (FLASH->STATR & FLASH_STATR_BSY); // Wait for erase
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// Write new seed
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FLASH->CTLR = CR_PAGE_PG;
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FLASH->CTLR = CR_BUF_RST | CR_PAGE_PG;
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FLASH->ADDR = (intptr_t)FLASH_SEED_ADDR;
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((uint32_t *)FLASH_SEED_ADDR)[0] = (uint32_t)seed;
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((uint32_t *)FLASH_SEED_ADDR)[1] = (uint32_t)(seed >> 32);
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FLASH->CTLR = CR_PAGE_PG | FLASH_CTLR_BUF_LOAD;
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while (FLASH->STATR & FLASH_STATR_BSY); // Wait for completion
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FLASH->CTLR = CR_PAGE_PG | CR_STRT_Set; // Commit write
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while (FLASH->STATR & FLASH_STATR_BSY); // Wait for completion
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}
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