NSData+Base64.m

//
//  NSData+Base64.m
//
//  Version 1.0.2
//
//  Created by Nick Lockwood on 12/01/2012.
//  Copyright (C) 2012 Charcoal Design
//
//  Distributed under the permissive zlib License
//  Get the latest version from here:
//
//  https://github.com/nicklockwood/Base64
//
//  This software is provided 'as-is', without any express or implied
//  warranty.  In no event will the authors be held liable for any damages
//  arising from the use of this software.
//
//  Permission is granted to anyone to use this software for any purpose,
//  including commercial applications, and to alter it and redistribute it
//  freely, subject to the following restrictions:
//
//  1. The origin of this software must not be misrepresented; you must not
//  claim that you wrote the original software. If you use this software
//  in a product, an acknowledgment in the product documentation would be
//  appreciated but is not required.
//
//  2. Altered source versions must be plainly marked as such, and must not be
//  misrepresented as being the original software.
//
//  3. This notice may not be removed or altered from any source distribution.
//

#import "NSData+Base64.h"

@implementation NSData (Base64)

+ (NSData *)dataWithBase64EncodedString:(NSString *)string
{
    const char lookup[] =
    {
        99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 
        99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 
        99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 62, 99, 99, 99, 63, 
        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 99, 99, 99, 99, 99, 99, 
        99,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 
        15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 99, 99, 99, 99, 99, 
        99, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 
        41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 99, 99, 99, 99, 99
    };
    
    NSData *inputData = [string dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
    long long inputLength = [inputData length];
    const unsigned char *inputBytes = [inputData bytes];
    
    long long maxOutputLength = (inputLength / 4 + 1) * 3;
    NSMutableData *outputData = [NSMutableData dataWithLength:maxOutputLength];
    unsigned char *outputBytes = (unsigned char *)[outputData mutableBytes];

    int accumulator = 0;
    long long outputLength = 0;
    unsigned char accumulated[] = {0, 0, 0, 0};
    for (long long i = 0; i < inputLength; i++)
    {
        unsigned char decoded = lookup[inputBytes[i] & 0x7F];
        if (decoded != 99)
        {
            accumulated[accumulator] = decoded;
            if (accumulator == 3)
            {
                outputBytes[outputLength++] = (accumulated[0] << 2) | (accumulated[1] >> 4);  
                outputBytes[outputLength++] = (accumulated[1] << 4) | (accumulated[2] >> 2);  
                outputBytes[outputLength++] = (accumulated[2] << 6) | accumulated[3];
            }
            accumulator = (accumulator + 1) % 4;
        }
    }
    
    //handle left-over data
    if (accumulator > 0) outputBytes[outputLength] = (accumulated[0] << 2) | (accumulated[1] >> 4);
    if (accumulator > 1) outputBytes[++outputLength] = (accumulated[1] << 4) | (accumulated[2] >> 2);
    if (accumulator > 2) outputLength++;
    
    //truncate data to match actual output length
    outputData.length = outputLength;
    return outputLength? outputData: nil;
}

- (NSString *)base64EncodedStringWithWrapWidth:(NSUInteger)wrapWidth
{
    //ensure wrapWidth is a multiple of 4
    wrapWidth = (wrapWidth / 4) * 4;
    
    const char lookup[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
    
    long long inputLength = [self length];
    const unsigned char *inputBytes = [self bytes];
    
    long long maxOutputLength = (inputLength / 3 + 1) * 4;
    maxOutputLength += wrapWidth? (maxOutputLength / wrapWidth) * 2: 0;
    unsigned char *outputBytes = (unsigned char *)malloc(maxOutputLength);
    
    long long i;
    long long outputLength = 0;
    for (i = 0; i < inputLength - 2; i += 3)
    {
        outputBytes[outputLength++] = lookup[(inputBytes[i] & 0xFC) >> 2];
        outputBytes[outputLength++] = lookup[((inputBytes[i] & 0x03) << 4) | ((inputBytes[i + 1] & 0xF0) >> 4)];
        outputBytes[outputLength++] = lookup[((inputBytes[i + 1] & 0x0F) << 2) | ((inputBytes[i + 2] & 0xC0) >> 6)];
        outputBytes[outputLength++] = lookup[inputBytes[i + 2] & 0x3F];
        
        //add line break
        if (wrapWidth && (outputLength + 2) % (wrapWidth + 2) == 0)
        {
            outputBytes[outputLength++] = '\r';
            outputBytes[outputLength++] = '\n';
        }
    }
    
    //handle left-over data
    if (i == inputLength - 2)
    {
        // = terminator
        outputBytes[outputLength++] = lookup[(inputBytes[i] & 0xFC) >> 2];
        outputBytes[outputLength++] = lookup[((inputBytes[i] & 0x03) << 4) | ((inputBytes[i + 1] & 0xF0) >> 4)];
        outputBytes[outputLength++] = lookup[(inputBytes[i + 1] & 0x0F) << 2];
        outputBytes[outputLength++] =   '=';
    }
    else if (i == inputLength - 1)
    {
        // == terminator
        outputBytes[outputLength++] = lookup[(inputBytes[i] & 0xFC) >> 2];
        outputBytes[outputLength++] = lookup[(inputBytes[i] & 0x03) << 4];
        outputBytes[outputLength++] = '=';
        outputBytes[outputLength++] = '=';
    }
    
    //truncate data to match actual output length
    outputBytes = realloc(outputBytes, outputLength);
    NSString *result = [[NSString alloc] initWithBytesNoCopy:outputBytes length:outputLength encoding:NSASCIIStringEncoding freeWhenDone:YES];

#if !__has_feature(objc_arc)
    [result autorelease];
#endif
    
    return (outputLength >= 4)? result: nil;
}

- (NSString *)base64EncodedString
{
    return [self base64EncodedStringWithWrapWidth:0];
}

@end