Custom NSURLProtocol class for WebView doesn't work when loading video in HTML5 document

Question

I'm working with WebView which loads its contents from certain location like sandbox. So I added simple child class of NSURLProtocol to handle those files. The protocol handler will manage URL scheme like "dummy:". When I tried custom url like dummy:///index.html, this should load index.html from a local directory. Htmls and embedded images etc. worked fine.

But when I tried an html file includes HTML5 video player using tag, it doesn't work. WebView even didn't tried the method canInitWithRequest:request in my custom class for the video file.

@interface DummyURLProtocol : NSURLProtocol {
}

+ (BOOL)canInitWithRequest:(NSURLRequest *)request;
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request;
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b;
- (void)startLoading;
- (void)stopLoading;

@end

@implementation DummyURLProtocol

+(BOOL)canInitWithRequest:(NSURLRequest *)request {
    return [[[request URL] scheme] isEqualToString:@"dummy"];
}

+(NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
    return request;
}

+(BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b {
    return [[[a URL] resourceSpecifier] isEqualToString:[[b URL] resourceSpecifier]];
}

-(void)startLoading {
    NSURL *url = [[self request] URL];
    NSString *pathString = [url resourceSpecifier];
    NSString *path = [NSString stringWithFormat:@"/Users/cronos/tmp/video_demo/%@", pathString];
    NSString *fullFilename = [pathString lastPathComponent];
    NSString *extention = [fullFilename pathExtension];
    NSString *mimeType = [[SSGHTMLUtil sharedUtil] mimeTypeForExtension:extention];
    NSLog(@"DummyURLProtocol:FILEPATH: %@ EXTENSION: %@ MIME-TYPE: %@", path, extention, mimeType);


    NSURLResponse *response = [[NSURLResponse alloc] initWithURL:url MIMEType:mimeType expectedContentLength:-1 textEncodingName:nil];
    FILE *fp = fopen([path UTF8String], "r");
    if (fp) {
        char buf[32768];
        size_t len;
        [[self client] URLProtocol:self
                didReceiveResponse:response
                cacheStoragePolicy:NSURLCacheStorageNotAllowed];
        while ((len = fread(buf,1,sizeof(buf),fp))) {
            [[self client] URLProtocol:self didLoadData:[NSData dataWithBytes:buf length:len]];
        }
        fclose(fp);
    }
    [[self client] URLProtocolDidFinishLoading:self];
}

-(void)stopLoading {
}

@end

I registered the protocol handler in applicationDidFinishLaunching: in AppDelegate.m

if ([NSURLProtocol registerClass:[DummyURLProtocol class]]) {
    NSLog(@"URLProtocol registration successful.");
} else {
    NSLog(@"URLProtocol registration failed.");
}

then I tried my WebView with the url "dummy:///HTML5_Video.html". Other resources like javascript files, css files, images are loaded successfully but mp4 file wasn't passed to the DummyURLProtocol. The HTML5_Video.html includes following.

  <video preload="metadata"> <!-- https://bugzilla.mozilla.org/show_bug.cgi?id=676422 -->
    <source src="assets/dizzy.mp4" type="video/mp4" />
    <source src="assets/dizzy.webm" type="video/webm" />
    <source src="assets/dizzy.ogv" type="video/ogv" />
  </video>

Any ideas or good starting point to solve this problem?

Thank you.

Answer 1

Yup. It won't work.

I've filed bugs with Apple over a year ago.

Video and other multimedia types including SVG do not go through the NSURLProtocol mechanism

See http://openradar.appspot.com/8446587

and http://openradar.appspot.com/8692954