bluesniff/hopping.c at main · lexfo/bluesniff · GitHub

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/*
 * This file is part of the Bluesniff project.
 * Copyright (C) 2025 LEXFO
 */

#include <stdint.h>

static uint16_t perm(uint16_t v) {
	v = ((v & 0x5555) << 1) | ((v & 0xAAAA) >> 1);
	v = ((v & 0x3333) << 2) | ((v & 0xCCCC) >> 2);
	v = ((v & 0x0F0F) << 4) | ((v & 0xF0F0) >> 4);
	return v;
}

static uint16_t channelId(uint32_t aa) { return (aa >> 16) ^ (aa & 0xFFFF); }

static uint16_t mam(uint16_t a, uint16_t b) { return (17 * a + b) & 0xFFFF; }

static uint16_t eventPrng(uint16_t counter, uint16_t channelId) {
	uint16_t res = counter ^ channelId;
	res = perm(res);
	res = mam(res, channelId);
	res = perm(res);
	res = mam(res, channelId);
	res = perm(res);
	res = mam(res, channelId);
	res = res ^ channelId;
	return res;
}

static uint16_t unmappedChannel(uint16_t prn_e) { return prn_e % 37; }

uint16_t getChannel(uint16_t counter, uint32_t aa) {
	uint16_t res = unmappedChannel(eventPrng(counter, channelId(aa)));
	return res;
}