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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>
const char HEX_DIGITS[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
static inline int to_nibble(char *bin) {
char *endptr = NULL;
char *dup = strndup(bin, 4);
int result = strtol(dup, &endptr, 2);
if (dup + strlen(dup) != endptr) {
free(dup);
return -1;
}
free(dup);
return result;
}
char *pad_to_n(char *str, size_t n) {
size_t len = (strlen(str) / n + 1) * n;
char *out = calloc(len + 1, sizeof(char));
char *ptr = out;
for (size_t i = 0; i < len - strlen(str); i++) {
*ptr = '0';
ptr++;
}
while (*str) {
*ptr = *str;
ptr++;
str++;
}
return out;
}
char *bin_to_hex(char *num) {
char *padded = pad_to_n(num, 8);
char *ptr = padded;
char *end = padded + strlen(padded);
char *out = calloc(strlen(padded) / 4 + 1, sizeof(char));
size_t i = 0;
while (ptr < end) {
int num = to_nibble(ptr);
if (num == -1) {
free(padded);
free(out);
return NULL;
}
out[i] = HEX_DIGITS[num];
ptr += 4;
i++;
}
free(padded);
return out;
}