A simple CFNetwork wrapper

YSNetwork.h

#import <Foundation/Foundation.h>

@interface YSNetwork : NSObject
@property (readonly) NSURL *URL;
@property (strong, nonatomic) NSURLRequest *request;
@property (strong, nonatomic) NSString *userAgent;
@property (strong, nonatomic, readonly) NSData *responseData;
@property (strong, nonatomic, readonly) NSDictionary *responseHeader;
@property (strong, nonatomic) void (^completion)(NSDictionary *responseHeader, NSData *responseData);
@property (strong, nonatomic) void (^failure)(NSError *error);

- (void)start;
- (void)startSynchronous;

@end

YSNetwork.m

#import "YSNetwork.h"

@interface YSNetwork ()
@property (strong, nonatomic) NSMutableData *buffer;
@property (strong, nonatomic) NSData *responseData;
@property (strong, nonatomic) NSDictionary *responseHeader;
@end

@implementation YSNetwork

- (NSURL *)URL
{
    return self.request.URL;
}

- (void)start
{
    CFReadStreamRef stream = [self prepare];
    if (stream) {
        dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
        dispatch_async(q, ^{
            [self pollingStream:stream];
        });
    }
    else {
        [self raiseError:stream];
    }
}

- (void)startSynchronous
{
    CFReadStreamRef stream = [self prepare];
    [self pollingStream:stream];
}

- (CFReadStreamRef)prepare
{
    self.buffer = NSMutableData.data;

    CFHTTPMessageRef message =
        CFHTTPMessageCreateRequest(kCFAllocatorDefault, (CFStringRef)@"GET",
                                   (__bridge CFURLRef)(self.URL), kCFHTTPVersion1_1);
    for (NSString *field in self.request.allHTTPHeaderFields) {
        NSString *value = self.request.allHTTPHeaderFields[field];
        CFHTTPMessageSetHeaderFieldValue(message,
                                         (__bridge CFStringRef)field,
                                         (__bridge CFStringRef)value);
    }
    CFReadStreamRef stream = CFReadStreamCreateForHTTPRequest(kCFAllocatorDefault, message);
    BOOL open = CFReadStreamOpen(stream);

    return open ? stream : NULL;
}

- (void)pollingStream:(CFReadStreamRef)stream
{
    BOOL done = NO;
    NSDate *timeout = [NSDate dateWithTimeIntervalSinceNow:300];
    NSDictionary *header = nil;
    NSUInteger contentLength = 0;
    while (!done) {
        if (!CFReadStreamHasBytesAvailable(stream)) {
            if ([NSDate.date timeIntervalSinceDate:timeout] > 0) {
                [self raiseError:stream];
                break;
            }
            continue;
        }

        if (!header) {
            CFHTTPMessageRef response =
                (CFHTTPMessageRef)CFReadStreamCopyProperty(stream, kCFStreamPropertyHTTPResponseHeader);
            header = CFBridgingRelease(CFHTTPMessageCopyAllHeaderFields(response));
            contentLength = (NSUInteger)[header[@"Content-Length"] integerValue];
            CFRelease(response);

            self.responseHeader = header;
        }
        UInt8 buf[1024];
        CFIndex read = CFReadStreamRead(stream, buf, 1024);
        if (read < 0) {
            [self raiseError:stream];
        }
        else {
            [self.buffer appendBytes:buf length:read];
            if (self.buffer.length == contentLength) {
                self.responseData = self.buffer;
                if (self.completion) {
                    self.completion(header, self.buffer);
                }
                done = YES;
            }
        }
    }
    CFReadStreamClose(stream);
    CFRelease(stream);
}

- (void)raiseError:(CFReadStreamRef)stream
{
    CFErrorRef e = CFReadStreamCopyError(stream);
    if (self.failure) {
        self.failure((__bridge NSError *)(e));
    }
    CFRelease(e);
}

@end