NSString+BaseConvertion

NSString+BaseConvertion.h

//
//  NSString+BaseConvertion.h
//
//  Created by Guilherme Araújo on 31/05/14.
//  Copyright (c) 2014 Guilherme Araújo. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (BaseConvertion)

+ (NSString *)stringWithInteger:(NSUInteger)number onBase:(NSUInteger)base padding:(NSUInteger)padding;
- (NSUInteger)integerFromBase:(NSUInteger)base;

@end

NSString+BaseConvertion.m

//
//  NSString+BaseConvertion.m
//
//  Created by Guilherme Araújo on 31/05/14.
//  Copyright (c) 2014 Guilherme Araújo. All rights reserved.
//

#import "NSString+BaseConvertion.h"

@implementation NSString (BaseConvertion)

+ (NSString *)stringWithInteger:(NSUInteger)number onBase:(NSUInteger)base padding:(NSUInteger)padding {
  if (base < 2 || base > 62) {
    NSLog(@"NSString+BaseConvertion: invalid base. Base must be a value between 2 and 62");
    return nil;
  }
  
  NSString *alphabet = @"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  NSMutableString *encoded = [[NSMutableString alloc] init];
  
  do {
    [encoded insertString:[alphabet substringWithRange:NSMakeRange(number % base, 1)] atIndex:0];
  } while (number /= base);
  
  while ([encoded length] < padding) {
    [encoded insertString:@"0" atIndex:0];
  }
  
  return encoded;
}

- (NSUInteger)integerFromBase:(NSUInteger)base {
  if (base < 2 || base > 62) {
    NSLog(@"NSString+BaseConvertion: invalid base. Base must be a value between 2 and 62");
    return -1;
  }
  
  NSString *alphabet = @"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  NSUInteger number = 0;
  
  for (NSUInteger power = [self length]; power > 0; power--) {
    NSUInteger value = [alphabet rangeOfString:[self substringWithRange:NSMakeRange(power - 1, 1)]].location;
    number += value * (NSUInteger)pow(base, [self length] - power);
  }
  
  return number;
}

@end