NSString+LolayBase64.m

//
//  Copyright 2012 Lolay, Inc.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

#import "NSString+LolayBase64.h"

static const short _base64DecodingTable[256] = {
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -2, -1, -1, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, -2, -2, 63,
	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2, -2, -2, -2,
	-2,  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, -2, -2, -2, -2, -2,
	-2, 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, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
	-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
};

@implementation NSString (LolayBase64)

- (NSData*) base64DataWithEncoding:(NSStringEncoding) encoding {
	const char * objPointer = [self cStringUsingEncoding:encoding];
	if (objPointer == NULL)  return nil;
	size_t intLength = strlen(objPointer);
	int intCurrent;
	int i = 0, j = 0, k;
	
	unsigned char * objResult;
	objResult = calloc(intLength, sizeof(char));
	
	// Run through the whole string, converting as we go
	while ( ((intCurrent = *objPointer++) != '\0') && (intLength-- > 0) ) {
		if (intCurrent == '=') {
			if (*objPointer != '=' && ((i % 4) == 1)) {// || (intLength > 0)) {
				// the padding character is invalid at this point -- so this entire string is invalid
				free(objResult);
				return nil;
			}
			continue;
		}
		
		intCurrent = _base64DecodingTable[intCurrent];
		if (intCurrent == -1) {
			// we're at a whitespace -- simply skip over
			continue;
		} else if (intCurrent == -2) {
			// we're at an invalid character
			free(objResult);
			return nil;
		}
		
		switch (i % 4) {
			case 0:
				objResult[j] = intCurrent << 2;
				break;
				
			case 1:
				objResult[j++] |= intCurrent >> 4;
				objResult[j] = (intCurrent & 0x0f) << 4;
				break;
				
			case 2:
				objResult[j++] |= intCurrent >>2;
				objResult[j] = (intCurrent & 0x03) << 6;
				break;
				
			case 3:
				objResult[j++] |= intCurrent;
				break;
		}
		i++;
	}
	
	// mop things up if we ended on a boundary
	k = j;
	if (intCurrent == '=') {
		switch (i % 4) {
			case 1:
				// Invalid state
				free(objResult);
				return nil;
				
			case 2:
				k++;
				// flow through
			case 3:
				objResult[k] = 0;
		}
	}
	
	// Cleanup and setup the return NSData
	return [NSData dataWithBytesNoCopy:objResult length:j freeWhenDone:YES];
}

+ (NSData*) base64DataWithString:(NSString*) base64String encoding:(NSStringEncoding) encoding {
	return [base64String base64DataWithEncoding:encoding];
}

- (NSData*) base64Data {
	return [self base64DataWithEncoding:NSUTF8StringEncoding];
}

+ (NSData*) base64DataWithString:(NSString*) base64String {
	return [base64String base64DataWithEncoding:NSUTF8StringEncoding];
}

@end