base64encoding

NSData+Additions.h

//
//  NSData+Additions.h
//
//  Created by Samuel Chow on 4/26/11.
//  Copyright 2011 MobyFab. All rights reserved.
//

@interface NSData (MBBase64)

+ (id)dataWithBase64EncodedString:(NSString *)string;     //  Padding '=' characters are optional. Whitespace is ignored.
- (NSString *)base64Encoding;

@end

NSData+Additions.m

//
//  NSData+Additions.m
//
//  Created by Samuel Chow on 4/26/11.
//  Copyright 2011 MobyFab. All rights reserved.
//
//  Credits: http://www.cocoadev.com/index.pl?BaseSixtyFour
//

#import "NSData+Additions.h"

static const char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

@implementation NSData (MBBase64)

+ (id)dataWithBase64EncodedString:(NSString *)string {
  if (string == nil)
    [NSException raise:NSInvalidArgumentException format:nil];
  if ([string length] == 0)
    return [NSData data];
  
  static char *decodingTable = NULL;
  if (decodingTable == NULL) {
    decodingTable = malloc(256);
    if (decodingTable == NULL)
      return nil;
    memset(decodingTable, CHAR_MAX, 256);
    NSUInteger i;
    for (i = 0; i < 64; i++)
      decodingTable[(short)encodingTable[i]] = i;
  }
  
  const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding];
  if (characters == NULL)     //  Not an ASCII string!
    return nil;
  char *bytes = malloc((([string length] + 3) / 4) * 3);
  if (bytes == NULL)
    return nil;
  NSUInteger length = 0;
  
  NSUInteger i = 0;
  while (YES)
  {
    char buffer[4];
    short bufferLength;
    for (bufferLength = 0; bufferLength < 4; i++)
    {
      if (characters[i] == '\0')
        break;
      if (isspace(characters[i]) || characters[i] == '=')
        continue;
      buffer[bufferLength] = decodingTable[(short)characters[i]];
      if (buffer[bufferLength++] == CHAR_MAX)      //  Illegal character!
      {
        free(bytes);
        return nil;
      }
    }
    
    if (bufferLength == 0)
      break;
    if (bufferLength == 1)      //  At least two characters are needed to produce one byte!
    {
      free(bytes);
      return nil;
    }
    
    //  Decode the characters in the buffer to bytes.
    bytes[length++] = (buffer[0] << 2) | (buffer[1] >> 4);
    if (bufferLength > 2)
      bytes[length++] = (buffer[1] << 4) | (buffer[2] >> 2);
    if (bufferLength > 3)
      bytes[length++] = (buffer[2] << 6) | buffer[3];
  }
  
  realloc(bytes, length);
  return [NSData dataWithBytesNoCopy:bytes length:length];
}

- (NSString *)base64Encoding {
  if ([self length] == 0)
    return @"";
  
  char *characters = malloc((([self length] + 2) / 3) * 4);
  if (characters == NULL)
    return nil;
  NSUInteger length = 0;
  
  NSUInteger i = 0;
  while (i < [self length])
  {
    char buffer[3] = {0,0,0};
    short bufferLength = 0;
    while (bufferLength < 3 && i < [self length])
      buffer[bufferLength++] = ((char *)[self bytes])[i++];
    
    //  Encode the bytes in the buffer to four characters, including padding "=" characters if necessary.
    characters[length++] = encodingTable[(buffer[0] & 0xFC) >> 2];
    characters[length++] = encodingTable[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];
    if (bufferLength > 1)
      characters[length++] = encodingTable[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];
    else characters[length++] = '=';
    if (bufferLength > 2)
      characters[length++] = encodingTable[buffer[2] & 0x3F];
    else characters[length++] = '=';  
  }
  
  return [[[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES] autorelease];
}

@end