Converting NSData to base64 - iphone

Question

How to convert NSData to base64. I have NSData and want to convert into base64 how can I do this?

Answer 1

EDIT
As of OS X 10.9 / iOS 7, this is built into the frameworks.
See -[NSData base64EncodedDataWithOptions:]
Prior to iOS7/OS X 10.9:
Matt Gallagher wrote an article on this very topic. At the bottom he gives a link to his embeddable code for iPhone.
On the mac you can use the OpenSSL library, on the iPhone he writes his own impl.

Answer 2

//from: http://cocoadev.com/BaseSixtyFour
+ (NSString*)base64forData:(NSData*)theData {
const uint8_t* input = (const uint8_t*)[theData bytes];
NSInteger length = [theData length];
static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
NSMutableData* data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
uint8_t* output = (uint8_t*)data.mutableBytes;
NSInteger i;
for (i=0; i < length; i += 3) {
NSInteger value = 0;
NSInteger j;
for (j = i; j < (i + 3); j++) {
value <<= 8;
if (j < length) {
value |= (0xFF & input[j]);
}
}
NSInteger theIndex = (i / 3) * 4;
output[theIndex + 0] = table[(value >> 18) & 0x3F];
output[theIndex + 1] = table[(value >> 12) & 0x3F];
output[theIndex + 2] = (i + 1) < length ? table[(value >> 6) & 0x3F] : '=';
output[theIndex + 3] = (i + 2) < length ? table[(value >> 0) & 0x3F] : '=';
}
return [[[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding] autorelease];
}

Answer 3

As an update, the iOS7 SDK has a category on NSData (NSDataBase64Encoding) with methods
-[NSData base64EncodedStringWithOptions:]
-[NSData initWithBase64EncodedString:options:]
-[NSData initWithBase64EncodedData:options:]
-[NSData base64EncodedDataWithOptions:]
Should avoid having to roll your own category method

Answer 4

Super easy drop-in Google library code here.
Just use +rfc4648Base64StringEncoding to get an instance, then use the encode/decode functions.
It's a beautiful thing. (Don't forget to grab the header file and the GTMDefines.h header from the root, though.)

Answer 5

Its not easy. As in there's no built in support for this in c or obj-c. Here's what Im doing (Which is basically having the CL do it for me):
- (NSString *)_base64Encoding:(NSString *) str
{
NSTask *task = [[[NSTask alloc] init] autorelease];
NSPipe *inPipe = [NSPipe pipe], *outPipe = [NSPipe pipe];
NSFileHandle *inHandle = [inPipe fileHandleForWriting], *outHandle = [outPipe fileHandleForReading];
NSData *outData = nil;
[task setLaunchPath:#"/usr/bin/openssl"];
[task setArguments:[NSArray arrayWithObjects:#"base64", #"-e", nil]];
[task setStandardInput:inPipe];
[task setStandardOutput:outPipe];
[task setStandardError:outPipe];
[task launch];
[inHandle writeData:[str dataUsingEncoding: NSASCIIStringEncoding]];
[inHandle closeFile];
[task waitUntilExit];
outData = [outHandle readDataToEndOfFile];
if (outData)
{
NSString *base64 = [[[NSString alloc] initWithData:outData encoding:NSUTF8StringEncoding] autorelease];
if (base64)
return base64;
}
return nil;
}
And you use it like this:
NSString *b64str = [strToConvert _base64Encoding:strToConvert];
And this isn't my code - I found it here: http://www.cocoadev.com/index.pl?BaseSixtyFour and it works great. You could always turn this into a +() method.
Oh, and to get your NSData to an NSString for this method:
NSString *str = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];

Answer 6

iOS has always included built in support for base64 encoding and decoding. If you look at resolv.h you should see the two functions b64_ntop and b64_pton . The Square SocketRocket library provides a reasonable example of how to use these functions from objective-c.
These functions are pretty well tested and reliable - unlike many of the implementations you may find in random internet postings.
Don't forget to link against libresolv.dylib.
If you link against the iOS 7 SDK, you can use the newer methods initWithBase64Encoding: and base64EncodedDataWithOptions:. These exist in previous releases, but were private. So if you link against the 6 SDK, you may run into undefined behavior. This would be an example of how to use this only when linking against the 7 SDK:
#ifndef __IPHONE_7_0
// oh no! you are using something unsupported!
// Call and implementation that uses b64_pton here
#else
data = [[NSData alloc] initWithBase64Encoding:string];
#endif

Answer 7

I modified the code above to meet my needs, building an HTTP POST. I was able to skip the NSString step, and include line breaks in the BASE64 code, which at least one web server found more palatable:
#define LINE_SIZE 76
//originally from: http://www.cocoadev.com/index.pl?BaseSixtyFour
// via joshrl on stockoverflow
- (void) appendBase64Of: (NSData *)inData to:(NSMutableData *)outData {
const uint8_t* input = (const uint8_t*)[inData bytes];
NSInteger length = [inData length];
static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
uint8_t buf[LINE_SIZE + 4 + 2];
size_t n = 0;
NSInteger i;
for (i=0; i < length; i += 3) {
NSInteger value = 0;
NSInteger j;
for (j = i; j < (i + 3); j++) {
value <<= 8;
if (j < length) {
value |= (0xFF & input[j]);
}
}
buf[n + 0] = table[(value >> 18) & 0x3F];
buf[n + 1] = table[(value >> 12) & 0x3F];
buf[n + 2] = (i + 1) < length ? table[(value >> 6) & 0x3F] : '=';
buf[n + 3] = (i + 2) < length ? table[(value >> 0) & 0x3F] : '=';
n += 4;
if (n + 2 >= LINE_SIZE) {
buf[n++] = '\r';
buf[n++] = '\n';
[outData appendBytes:buf length:n];
n = 0;
}
}
if (n > 0) {
buf[n++] = '\r';
buf[n++] = '\n';
[outData appendBytes:buf length:n];
}
return;
}