c base64 encoder

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

char *base64encode(char *input);

int main(int argc, char **argv) {
    if (argc != 2) {
        printf("Usage: example ... text\r\n");
        return 1;
    }
    char *text = argv[1];
    char *encoded_text = base64encode(text);
    printf("Input String: \"%s\"\r\nOutput String: \"%s\"\r\n", text, encoded_text);
    free(encoded_text);
    return 0;
}

char *base64encode(char *input) {
    int len = strlen(input), padding = (len % 3)?3 - (len % 3):0, n, xlen = 0;
    size_t bitlen = len * 8;
    uint8_t *x = malloc(((int)(bitlen / 24) * 4) + ((padding)?4:0)), i, o;
    for (n = 0; n < len; n++) {
        switch (n % 3) {
            case 0:
                i = (uint8_t)(input[n] >> 2);
                x[xlen++] = i;
                break;
            case 1:
                i = (uint8_t)((input[n-1] & 3) << 4);
                o = (uint8_t)((input[n] & 240) >> 4);
                x[xlen++] = i | o;
                break;
            case 2:
                i = (uint8_t)((input[n-1] & 15) << 2);
                o = (uint8_t)((input[n] & 192) >> 6);
                x[xlen++] = i | o;
                i = (uint8_t)(input[n] & 63);
                x[xlen++] = i;
                break;
        }
        if ((len - n) == ((padding==2)?2:3) && padding > 0) {
            n++;
            break;
        }
    }
    if (padding == 2) {
        i = (uint8_t)(input[n] >> 2);
        x[xlen++] = i;
        i = (uint8_t)((input[n] & 3) << 4);
        x[xlen++] = i;
    } else if (padding == 1) {
        i = (uint8_t)(input[n] >> 2);
        x[xlen++] = i;
        i = (uint8_t)((input[n] & 3) << 4);
        o = (uint8_t)((input[n+1] & 240) >> 4);
        x[xlen++] = i | o;
        i = (uint8_t)((input[n+1] & 15) << 2);
        x[xlen++] = i;
    }
    const char *index = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    char *returnString = malloc((int)((bitlen / 24) + padding) * 4 + 1);
    for (n = 0; n < ((int)(bitlen / 24) * 4) + ((padding)?4:0) - padding; n++) {
        returnString[n] = index[x[n]];
    }
    free(x);
    for (;padding > 0; padding--) {
        returnString[n++] = '=';
    }
    returnString[n] = '\0';
    return returnString;
}