Base64 in C

base64.c

#include <stdlib.h>
#include "base64.h"

static char values[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

static int indexOf(char * array, char value){
	int i;
	for(i = 0; *array; ++i, ++array)
		if(*array == value)
			return i;

	return -1;
}

static unsigned long size(char * input){ 	//will calculate size up to 2^64-1 bytes
	long length = 0;
	while(*input++)
		length++;

	return length;
}

static char valid(char value){ 		//check to see if the char is valid
	return (value < 64 && value >= 0) ? 1 : 0;
}

static unsigned char * getMem(unsigned long inputSize, char value){
	return  malloc(1+ (value == ENCODE) ? ((inputSize * 4)/3): ((inputSize * 3)/4));
}

unsigned char *encode(char *input){
	unsigned long len = size(input), i;
	unsigned char *res = getMem(len, ENCODE), *p = res, b;

	for(i = 0; i < len; i += 3){
		b = (input[i] & 0xFC) >> 2;
		*p++ = values[b];
		b = (input[i] & 0x03) << 4;

		if(i+1 < len){
			b |= ((input[i+1] & 0xf0) >> 4);
			*p++ = values[b];
			b = (input[i+1] & 0x0F) << 2;

			if(i+2 < len){
				b |= (input[i+2] & 0xC0) >> 6;
				*p++ = values[b];
				b = (input[i+2] & 0x3F);
				*p++ = values[b];
			}else{
				*p++ = values[b];
				*p++ = values[64];
				*p++ = values[64];
			}
		}else{
			*p++ = values[b];
			*p++ = values[64];
		}
	}

	*p = '\0';
	return res;
}

unsigned char *decode(char *input){
	unsigned long len = size(input), i;
	unsigned char *res = getMem(len, DECODE), *p = res, b[4];

	for(i = 0; i < len; i += 4){
		int a;
		for(a = 0; a < 4; a++){
			b[a] = indexOf(values,input[i+a]);
		}

		if(!valid(b[0])){
			*p++ = (b[0] << 2);
		}else{
			*p++ =  (b[0] << 2) | ((valid(b[1])) ? (b[1] >> 4) : 0);
			if(valid(b[1])){
				*p++ = (b[1] << 4) | ((valid(b[2])) ? (b[2] >> 2) : 0);
				if(valid(b[2])){
					*p++ = (b[2] << 6) | ((valid(b[3])) ? b[3] : 0);
				}
			}
		}
	}

	*p = '\0';
	return res;
}

base64.h

#ifndef BASE64_H_
#define BASE64_H_

#define ENCODE 0
#define DECODE 1

unsigned char * encode(char * input);
unsigned char * decode(char * input);

#endif /* BASE64_H_ */

main.c

#include <stdio.h>
#include "base64.h"

int main(void){

	char * res = "This is an encoded message into base64 and should display properly without errors!!";

	printf("%s\n\n", res);

	char * encoded = encode(res);
	printf("%s\n\n", encoded);

	char * decoded = decode(encoded);
	printf("%s\n\n", decoded);

	return 0;
}