Get a number's binary representation and hex representation

show_binary_and_hex_of_a_number.c

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <regex.h>

#define TOTAL_TYPE_PATTERNS 2

enum number_type{
	TYPE_INT,
	TYPE_FLOAT,
	TYPE_INVALID = -1
};

void show_bytes(unsigned char *a, int n)
{
	int i = 0;
	for (;i<n;i++) {
		printf("%.2X ", a[i]);
	}
	printf("\n");
}


void show_bits(unsigned char *a, int n)
{
	int i, j;
	unsigned char b;
	for (i=0;i<n;i++) {
		for (j=0;j<8;j++) {
			b = ((((unsigned int)a[i]) <<(24+ j)) >> 31);
			printf("%d", b);
		}
		printf(" ");
	}
	printf("\n");
}

int reg_match(const char *pattern, const char *target)
{
	regex_t rgx;

	if (regcomp(&rgx, pattern, REG_EXTENDED | REG_NOSUB | REG_NEWLINE) != 0) {
		return -1;
	}
	int result =  regexec(&rgx, target, 0, NULL, 0);
	regfree(&rgx);
	return result;
}


enum number_type  get_type(const char *str)
{
	const char *patterns[] = {
	"^[0-9]{1,10}$", 
	"^([0-9]{1,6}\\.[[:digit:]]{1,6}(e-?[0-9]+)?)$"
	};

	int i;
	for (i=0;i<TOTAL_TYPE_PATTERNS;i++) {
		if (reg_match(patterns[i], str) == 0) {
			return i;
		}
	}

	return -1;
}


int main(int argc, char **argv)
{
	long a;
	float b;
	unsigned char *c;
	char *type_names[] = {"int", "float"};


	if (argc > 1)  {
		enum number_type type = get_type(argv[1]);
		printf("Number(%s) type is %s\n", argv[1], type_names[type]);
		switch (type) {
			case TYPE_INT:
				a = strtol(argv[1], NULL, 10);
				c = (unsigned char *)&a;
				break;
			case TYPE_FLOAT:
				b = strtof(argv[1], NULL);
				c = (unsigned char *)&b;
				printf("%f\n", b);
				break;
			case TYPE_INVALID:
				printf("No valid number to convert.\n");
				return 0;
		}

		printf("--- BINARY FORM ---\n");
		show_bits(c, 4);
		printf("--- HEX FORM ---\n");
		show_bytes(c, 4);
	}
	return 0;
}