utils.c

/**
 * @file utils.c
 * @author Lee Essen (lee.essen@nowonline.co.uk)
 * @brief 
 * @version 0.1
 * @date 2022-07-12
 * 
 * @copyright Copyright (c) 2022
 * 
 */

#include "utils.h"
#include "stdlib.h"

int hex_digit(char ch) {
    if (ch >= '0' && ch <= '9') return (ch - '0');
    if (ch >= 'a' && ch <= 'f') return (ch - ('a'-10));
    if (ch >= 'A' && ch <= 'F') return (ch - ('A'-10));
    return -1;
}

int hex_byte(char *packet) {
    int rc;
    int v;

    v = hex_digit(*packet++);
    if (v == -1)
        return -1;
    rc = v << 4;
    v = hex_digit(*packet);
    if (v == -1)
        return -1;
    rc |= v;
    return rc;
}

/**
 * @brief Read in 8 chars and convert into a litte endian word
 *
 */
uint32_t hex_word_le32(char *packet) {
    uint32_t rc = 0;

    for (int i = 0; i < 4; i++) {
        rc >>= 8;
        int v = hex_byte(packet);
        if (v == -1)
            return 0xffffffff;
        packet += 2;
        rc |= (v << 24);
    }
    return rc;
}

char *get_two_hex_numbers(char *packet, char sepch, uint32_t *one, uint32_t *two) {
    char *sep;
    char *end;

    *one = strtoul(packet, &sep, 16);
    if (*sep != sepch)
        return NULL;
    *two = strtoul(sep + 1, &end, 16);
    return end;
}

/**
 * @brief Convert a sequence of hex bytes into binary form in the same place, returning length
 * 
 * @param packet 
 * @param sep 
 * @return int 
 */
int hex_to_bin(char *packet) {
    int v;
    uint8_t *dst = (uint8_t *)packet;
    int len = 0;

    while((v = hex_byte(packet)) >= 0) {
        *dst++ = v;
        packet += 2;
        len++;
    }
    return len;
}