Category on NSMutableURLRequest that sets HTTP "Authorization" header for basic access authentication, using code appropriated from AFNetworking

NSMutableURLRequest+KDJBasicAuthentication.h

#import <Foundation/Foundation.h>

@interface NSMutableURLRequest (KDJBasicAuthentication)

// Sets the "Authorization" HTTP header to a basic authentication value
// with Base64-encoded username and password. This overwrites any existing
// value for this header.
- (void)setAuthorizationHeaderWithUsername:(NSString *)username
                                  password:(NSString *)password;

@end

NSMutableURLRequest+KDJBasicAuthentication.m

// This file contains code from the AFNetworking library, which is
// licensed under these terms:
//
// Copyright (c) 2011 Gowalla (http://gowalla.com/)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#import "NSMutableURLRequest+KDJBasicAuthentication.h"

@implementation NSMutableURLRequest (KDJBasicAuthentication)

// This function was copied from AFNetworking's AFHTTPClient.m
static NSString * Base64EncodedStringFromString(NSString *string) {
    NSData *data = [NSData dataWithBytes:[string UTF8String] length:[string lengthOfBytesUsingEncoding:NSUTF8StringEncoding]];
    NSUInteger length = [data length];
    NSMutableData *mutableData = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
    
    uint8_t *input = (uint8_t *)[data bytes];
    uint8_t *output = (uint8_t *)[mutableData mutableBytes];
    
    for (NSUInteger i = 0; i < length; i += 3) {
        NSUInteger value = 0;
        for (NSUInteger j = i; j < (i + 3); j++) {
            value <<= 8;
            if (j < length) {
                value |= (0xFF & input[j]);
            }
        }
        
        static uint8_t const kAFBase64EncodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
        
        NSUInteger idx = (i / 3) * 4;
        output[idx + 0] = kAFBase64EncodingTable[(value >> 18) & 0x3F];
        output[idx + 1] = kAFBase64EncodingTable[(value >> 12) & 0x3F];
        output[idx + 2] = (i + 1) < length ? kAFBase64EncodingTable[(value >> 6)  & 0x3F] : '=';
        output[idx + 3] = (i + 2) < length ? kAFBase64EncodingTable[(value >> 0)  & 0x3F] : '=';
    }
    
    return [[NSString alloc] initWithData:mutableData encoding:NSASCIIStringEncoding];
}

- (void)setAuthorizationHeaderWithUsername:(NSString *)username password:(NSString *)password {
    NSString *basicAuthCredentials = [NSString stringWithFormat:@"%@:%@", username, password];
    NSString *headerValue = [NSString stringWithFormat:@"Basic %@", Base64EncodedStringFromString(basicAuthCredentials)];
    [self setValue:headerValue forHTTPHeaderField:@"Authorization"];
}

@end