hex_str_to_binary.c

#include <stdbool.h>

unsigned int get_digit_value(char digit) {
    int n = digit - '0';
    if (n >= 0 && n<10) { return (unsigned int) n; }
    if ((digit == 'A') || (digit == 'a')) { return 10; }
    if ((digit == 'B') || (digit == 'b')) { return 11; }
    if ((digit == 'C') || (digit == 'c')) { return 12; }
    if ((digit == 'D') || (digit == 'd')) { return 13; }
    if ((digit == 'E') || (digit == 'e')) { return 14; }
    if ((digit == 'F') || (digit == 'f')) { return 15; }
    return -1;
}

int get_pair_value(char digit1, char digit2) {
    unsigned int v1 = get_digit_value(digit1);
    unsigned int v2 = get_digit_value(digit2);
    return (v1 == -1 || v2 == -1) ? -1 : v1 * 16 + v2;
}

bool hex_str_to_binary(const char *src, size_t size, unsigned char *dst) {
    bool isGood = false;
    if (size % 2 == 0) {
        isGood = true;
        for (size_t i = 0; i<size; i += 2) {
            int pv = get_pair_value(src[i], src[i + 1]);
            if (pv == -1) { isGood = false; break; }
            *dst = pv;
            dst++;
        }
    }
    // *dst = 0;
    return isGood;
}

void binary_to_hex_str(const unsigned char *src, size_t size, char *dst) {
    if (src == NULL || size == 0 || dst == NULL) {
        return;
    }
    for (size_t i = 0; i != size; ++i) {
        sprintf(dst, "%02X", src[i]);
        dst += 2;
    }
    *dst = '\0';
}

void str_to_upper(char *str) {
    if (str == NULL) {
        return;
    }
    for (int i = 0; str[i] != 0x00; i++) {
        if (str[i] >= 'a' && str[i] <= 'z') {
            str[i] -= 32;
        }
    }
}

int test(void) {
    char buffer[100] = { 0 };
    char RecvData[64] = "474F4420426C65737320416D657269636121";

    printf("%s\n", RecvData);
    printf("isGood = %d\n", hex_str_to_binary(RecvData, (size_t)strlen(RecvData), buffer));
    printf("%s\n", buffer);

    char buffer2[100];
    binary_to_hex_str(buffer, strlen(buffer), buffer2);
    printf("%s\n", buffer2);

    return 0;
}