NSData+MKBase64.m

//
//  NSData+MKNKBase64.m
//  base64
//
//  Created by Matt Gallagher on 2009/06/03.
//  Copyright 2009 Matt Gallagher. All rights reserved.
//
//  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+MKBase64.h"

//
// Mapping from 6 bit pattern to ASCII character.
//
static unsigned char base64EncodeLookup[65] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

//
// Definition for "masked-out" areas of the base64DecodeLookup mapping
//
#define xx 65

//
// Mapping from ASCII character to 6 bit pattern.
//
static unsigned char base64DecodeLookup[256] =
{
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 62, xx, xx, xx, 63, 
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, xx, xx, xx, xx, xx, xx, 
    xx,  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, xx, xx, xx, xx, xx, 
    xx, 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, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
    xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, 
};

//
// Fundamental sizes of the binary and base64 encode/decode units in bytes
//
#define BINARY_UNIT_SIZE 3
#define BASE64_UNIT_SIZE 4

//
// NewBase64Decode
//
// Decodes the base64 ASCII string in the inputBuffer to a newly malloced
// output buffer.
//
//  inputBuffer - the source ASCII string for the decode
//	length - the length of the string or -1 (to specify strlen should be used)
//	outputLength - if not-NULL, on output will contain the decoded length
//
// returns the decoded buffer. Must be free'd by caller. Length is given by
//	outputLength.
//
void *NewBase64Decode(
	const char *inputBuffer,
	size_t length,
	size_t *outputLength)
{
	if (length == -1)
	{
		length = strlen(inputBuffer);
	}
	
	size_t outputBufferSize =
		((length+BASE64_UNIT_SIZE-1) / BASE64_UNIT_SIZE) * BINARY_UNIT_SIZE;
	unsigned char *outputBuffer = (unsigned char *)malloc(outputBufferSize);
	
	size_t i = 0;
	size_t j = 0;
	while (i < length)
	{
		//
		// Accumulate 4 valid characters (ignore everything else)
		//
		unsigned char accumulated[BASE64_UNIT_SIZE];
		size_t accumulateIndex = 0;
		while (i < length)
		{
			unsigned char decode = base64DecodeLookup[inputBuffer[i++]];
			if (decode != xx)
			{
				accumulated[accumulateIndex] = decode;
				accumulateIndex++;
				
				if (accumulateIndex == BASE64_UNIT_SIZE)
				{
					break;
				}
			}
		}
		
		//
		// Store the 6 bits from each of the 4 characters as 3 bytes
		//
		// (Uses improved bounds checking suggested by Alexandre Colucci)
		//
		if(accumulateIndex >= 2)  
			outputBuffer[j] = (accumulated[0] << 2) | (accumulated[1] >> 4);  
		if(accumulateIndex >= 3)  
			outputBuffer[j + 1] = (accumulated[1] << 4) | (accumulated[2] >> 2);  
		if(accumulateIndex >= 4)  
			outputBuffer[j + 2] = (accumulated[2] << 6) | accumulated[3];
		j += accumulateIndex - 1;
	}
	
	if (outputLength)
	{
		*outputLength = j;
	}
	return outputBuffer;
}

//
// NewBase64Encode
//
// Encodes the arbitrary data in the inputBuffer as base64 into a newly malloced
// output buffer.
//
//  inputBuffer - the source data for the encode
//	length - the length of the input in bytes
//  separateLines - if zero, no CR/LF characters will be added. Otherwise
//		a CR/LF pair will be added every 64 encoded chars.
//	outputLength - if not-NULL, on output will contain the encoded length
//		(not including terminating 0 char)
//
// returns the encoded buffer. Must be free'd by caller. Length is given by
//	outputLength.
//
char *NewBase64Encode(
	const void *buffer,
	size_t length,
	bool separateLines,
	size_t *outputLength)
{
	const unsigned char *inputBuffer = (const unsigned char *)buffer;
	
	#define MAX_NUM_PADDING_CHARS 2
	#define OUTPUT_LINE_LENGTH 64
	#define INPUT_LINE_LENGTH ((OUTPUT_LINE_LENGTH / BASE64_UNIT_SIZE) * BINARY_UNIT_SIZE)
	#define CR_LF_SIZE 2
	
	//
	// Byte accurate calculation of final buffer size
	//
	size_t outputBufferSize =
			((length / BINARY_UNIT_SIZE)
				+ ((length % BINARY_UNIT_SIZE) ? 1 : 0))
					* BASE64_UNIT_SIZE;
	if (separateLines)
	{
		outputBufferSize +=
			(outputBufferSize / OUTPUT_LINE_LENGTH) * CR_LF_SIZE;
	}
	
	//
	// Include space for a terminating zero
	//
	outputBufferSize += 1;

	//
	// Allocate the output buffer
	//
	char *outputBuffer = (char *)malloc(outputBufferSize);
	if (!outputBuffer)
	{
		return NULL;
	}

	size_t i = 0;
	size_t j = 0;
	const size_t lineLength = separateLines ? INPUT_LINE_LENGTH : length;
	size_t lineEnd = lineLength;
	
	while (true)
	{
		if (lineEnd > length)
		{
			lineEnd = length;
		}

		for (; i + BINARY_UNIT_SIZE - 1 < lineEnd; i += BINARY_UNIT_SIZE)
		{
			//
			// Inner loop: turn 48 bytes into 64 base64 characters
			//
			outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0xFC) >> 2];
			outputBuffer[j++] = base64EncodeLookup[((inputBuffer[i] & 0x03) << 4)
				| ((inputBuffer[i + 1] & 0xF0) >> 4)];
			outputBuffer[j++] = base64EncodeLookup[((inputBuffer[i + 1] & 0x0F) << 2)
				| ((inputBuffer[i + 2] & 0xC0) >> 6)];
			outputBuffer[j++] = base64EncodeLookup[inputBuffer[i + 2] & 0x3F];
		}
		
		if (lineEnd == length)
		{
			break;
		}
		
		//
		// Add the newline
		//
		outputBuffer[j++] = '\r';
		outputBuffer[j++] = '\n';
		lineEnd += lineLength;
	}
	
	if (i + 1 < length)
	{
		//
		// Handle the single '=' case
		//
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0xFC) >> 2];
		outputBuffer[j++] = base64EncodeLookup[((inputBuffer[i] & 0x03) << 4)
			| ((inputBuffer[i + 1] & 0xF0) >> 4)];
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i + 1] & 0x0F) << 2];
		outputBuffer[j++] =	'=';
	}
	else if (i < length)
	{
		//
		// Handle the double '=' case
		//
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0xFC) >> 2];
		outputBuffer[j++] = base64EncodeLookup[(inputBuffer[i] & 0x03) << 4];
		outputBuffer[j++] = '=';
		outputBuffer[j++] = '=';
	}
	outputBuffer[j] = 0;
	
	//
	// Set the output length and return the buffer
	//
	if (outputLength)
	{
		*outputLength = j;
	}
	return outputBuffer;
}

@implementation NSData (MKNKBase64)

//
// dataFromBase64String:
//
// Creates an NSData object containing the base64 decoded representation of
// the base64 string 'aString'
//
// Parameters:
//    aString - the base64 string to decode
//
// returns the autoreleased NSData representation of the base64 string
//
+ (NSData *)dataFromBase64String:(NSString *)aString
{
	NSData *data = [aString dataUsingEncoding:NSASCIIStringEncoding];
	size_t outputLength;
	void *outputBuffer = NewBase64Decode([data bytes], [data length], &outputLength);
	NSData *result = [NSData dataWithBytes:outputBuffer length:outputLength];
	free(outputBuffer);
	return result;
}

//
// base64EncodedString
//
// Creates an NSString object that contains the base 64 encoding of the
// receiver's data. Lines are broken at 64 characters long.
//
// returns an autoreleased NSString being the base 64 representation of the
//	receiver.
//
- (NSString *)base64EncodedString
{
	size_t outputLength = 0;
	char *outputBuffer =
		NewBase64Encode([self bytes], [self length], false, &outputLength);
	
	NSString *result =
		[[NSString alloc]
			initWithBytes:outputBuffer
			length:outputLength
			encoding:NSASCIIStringEncoding];
	free(outputBuffer);
	return result;
}

@end