NSString - Base64 Encoding/Decoding

Base 64 Encoding

// .h
#import 

@interface NSString (NSStringAdditions)
+ (NSString *)base64StringFromData:(NSData *)data length:(int)length;
@end

 

// .m
#import "NSStringAdditions.h"

static char base64EncodingTable[64] = {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
	'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
	'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
};

@implementation NSString (NSStringAdditions)

+ (NSString *)base64StringFromData:(NSData *)data length:(int)length {
	unsigned long ixtext, lentext;
	long ctremaining;
	unsigned char input[3], output[4];
	short i, charsonline = 0, ctcopy;
	const unsigned char *raw;
	NSMutableString *result;

	lentext = [data length];
	if (lentext < 1)
		return @"";
	result = [NSMutableString stringWithCapacity:lentext];
	raw = [data bytes];
	ixtext = 0;

	while (true) {
		ctremaining = lentext - ixtext;
		if (ctremaining <= 0)
			break;
		for (i = 0; i < 3; i++) {
			unsigned long ix = ixtext + i;
			if (ix < lentext)
				input[i] = raw[ix];
			else
				input[i] = 0;
		}
		output[0] = (input[0] & 0xFC) >> 2;
		output[1] = ((input[0] & 0x03) << 4) | ((input[1] & 0xF0) >> 4);
		output[2] = ((input[1] & 0x0F) << 2) | ((input[2] & 0xC0) >> 6);
		output[3] = input[2] & 0x3F;
		ctcopy = 4;
		switch (ctremaining) {
			case 1:
				ctcopy = 2;
				break;

			case 2:
				ctcopy = 3;
				break;
		}

		for (i = 0; i < ctcopy; i++)
			[result appendString:[NSString stringWithFormat:@"%c", base64EncodingTable[output[i]]]];

		for (i = ctcopy; i < 4; i++)
			[result appendString:@"="];

		ixtext += 3;
		charsonline += 4;

		if ((length > 0) && (charsonline >= length))
			charsonline = 0;
	}
	return result;
}

@end

Base 64 Decoding

// .h
#import 

@class NSString;

@interface NSData (NSDataAdditions)
+ (NSData *)base64DataFromString:(NSString *)string;
@end

  

// .m
#import "NSDataAdditions.h"

@implementation NSData (NSDataAdditions)

+ (NSData *)base64DataFromString:(NSString *)string {
	unsigned long ixtext, lentext;
	unsigned char ch, inbuf[4], outbuf[3];
	short i, ixinbuf;
	Boolean flignore, flendtext = false;
	const unsigned char *tempcstring;
	NSMutableData *theData;

	if (string == nil)
		return [NSData data];

	ixtext = 0;
	tempcstring = (const unsigned char *)[string UTF8String];
	lentext = [string length];
	theData = [NSMutableData dataWithCapacity:lentext];
	ixinbuf = 0;

	while (true) {
		if (ixtext >= lentext)
			break;

		ch = tempcstring[ixtext++];
		flignore = false;

		if ((ch >= 'A') && (ch <= 'Z'))
			ch = ch - 'A';
		else if ((ch >= 'a') && (ch <= 'z'))
			ch = ch - 'a' + 26;
		else if ((ch >= '0') && (ch <= '9'))
			ch = ch - '0' + 52;
		else if (ch == '+')
			ch = 62;
		else if (ch == '=')
			flendtext = true;
		else if (ch == '/')
			ch = 63;
		else
			flignore = true;

		if (!flignore) {
			short ctcharsinbuf = 3;
			Boolean flbreak = false;

			if (flendtext) {
				if (ixinbuf == 0)
					break;

				if ((ixinbuf == 1) || (ixinbuf == 2))
					ctcharsinbuf = 1;
				else
					ctcharsinbuf = 2;

				ixinbuf = 3;
				flbreak = true;
			}

			inbuf[ixinbuf++] = ch;

			if (ixinbuf == 4) {
				ixinbuf = 0;

				outbuf[0] = (inbuf[0] << 2) | ((inbuf[1] & 0x30) >> 4);
				outbuf[1] = ((inbuf[1] & 0x0F) << 4) | ((inbuf[2] & 0x3C) >> 2);
				outbuf[2] = ((inbuf[2] & 0x03) << 6) | (inbuf[3] & 0x3F);

				for (i = 0; i < ctcharsinbuf; i++) {
					[theData appendBytes:&outbuf[i] length:1];
				}
			}

			if (flbreak)
				break;
		}
	}

	return theData;
}

@end