/**
 * Various utility functions for use by device drivers
 * 
 * Copyright (C) 2015 Tommy Vestermark
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#ifndef INCLUDE_UTIL_H_
#define INCLUDE_UTIL_H_

#include <stdint.h>
#include <time.h>

// Helper macros
#define max(a,b) ((a) > (b) ? (a) : (b))
#define min(a,b) ((a) < (b) ? (a) : (b))

/// Generic Cyclic Redundancy Check CRC-8
///
/// Example polynomial: 0x31 = x8 + x5 + x4 + 1	(x8 is implicit)
/// Example polynomial: 0x80 = x8 + x7			(a normal bit-by-bit parity XOR)
///
/// @param message[]: array of bytes to check
/// @param nBytes: number of bytes in message
/// @param polynomial: byte is from x^7 to x^0 (x^8 is implicitly one)
/// @return CRC value
uint8_t crc8(uint8_t const message[], unsigned nBytes, uint8_t polynomial);


// buffer to hold localized timestamp YYYY-MM-DD HH:MM:SS
#define LOCAL_TIME_BUFLEN	32

/// Printable timestamp in local time
///
/// @param time_secs: 0 for now, or seconds since the epoch
/// @param buf: output buffer, long enough for YYYY-MM-DD HH:MM:SS
void local_time_str(time_t time_secs, char *buf);

/**
 * convert unit from celsius to fahrenheit
 * @param celsius input temperature in Celsius
 * @return temperature value in Fahrenheit
 */
float celsius2fahrenheit(float celsius);

#endif /* INCLUDE_UTIL_H_ */