c语言如何用指针将十六进制字符串转换成二进制字符串？

Question

c语言如何用指针将十六进制字符串转换成二进制字符串？

Answer 1

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <ctype.h>

char x[17][5] =
{
  "0000", "0001", "0010", "0011",
  "0100", "0101", "0110", "0111",
  "1000", "1001", "1010", "1011",
  "1100", "1101", "1110", "1111",
};

int index_of_x(char c) {
  if (isdigit(c)) {
    return c - '0';
  } else if (isalpha(c)) {
    c = tolower(c);
    return (c - 'a') + 10;
  }
}

char* hex_to_bin(const char *hex_str) {
  int len = strlen(hex_str);
  char *bin_str = (char*)malloc(len * 4 + 1);
  const char *p = hex_str;
  char *q = bin_str;
  while (*p != '\0') {
    int idx = index_of_x(*p);
    memmove(q, x[idx], strlen(x[idx]));
    q += 4;
    p++;
  }
  *q = '\0';
  return bin_str;
}

int main() {
  const char hex_str[] = "ab14cb";
  char *dest = hex_to_bin(hex_str);
  printf("bin_str: %s\n", dest);
  free(dest);
  return 0;
}

抛砖引玉， 多多交流。

1 个 16 进制数对应 4 位二进制，把握住这点就可以了