Re: Caching Streaming video
I am trying to playback video in my iOS app while I am loading and caching it at the same time. I fetch the video using a NSURLConnection and then store it in a local file, I start video playback of the local video file after a certain number of bytes are received. I have it working great in the simulator, I can start playing the video before I have received all of it, but when I go to run my app on my iPodTouch, I can only seem to play up to the number of bytes I had already received before I started playback. I can only play the entire video if I wait until I have receive the entire file before I start playback. I can also get the video to play completely if I stop the failed attempt with a [video stop] message and then start playing it again, pausing the video only doesn't work. Has anybody got this working, is it possible. I haven't done this, but I would be interested in hearing about the solution you come up with. What you describe sounds like a bug worth filing a bug report on. I'll speculate the device implementation sees that you are opening a file and uses the number of bytes as a hint to the length of the video (incorrectly). So a random, not completely thought out idea...what if you created an intermediate local socket which you use to further separate the temporary file from the NSFileHandle. Maybe the implementation won't be able to find the file size if your NSFileHandle wraps a socket instead. -Eric -- Beginning iPhone Games Development http://playcontrol.net/iphonegamebook/ ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
dispatch_async Performance Issues
Hi All
I've implemented a typical consumer/producer pattern, using a container holding
a FIFO list of buffers. This buffer list has functions to store and retrieve
these buffers concurrently. Consumer and Producer are running in the global
concurrent dispatch queue.
I'm experiencing huge differences in performance in two almost identical
versions of the code. I've tried to figure the cause with Instruments, but
didn't find any concrete hints. The xxx_block_invoke of the consumer part of
one version just takes considerable more time than the other.
The code basically works as follows:
The producer is simply creating a certain amount of buffers (NSData objects),
initializing its content and storing them into the concurrent accessible buffer
list. The producer part of the code is identical in both versions. The
concurrently accessible buffers list is the same, too.
In the consumer part , the code simply retrieves buffers and processes them.
The difference is in the processing of the received buffer content - that is,
how the bytes of the buffer's content are accessed.
This tiny bit of difference in code should't make a huge difference in runtime,
but it actually there is a huge difference, where ever it comes from!
The first uses a direct implementation using pointers accessing the content
of the buffer.
The second implementation uses a C++ iterator concept. But when compiled with
-03, it should produce almost the same code as the former. So, I would expect
only minor differences in performance.
However, the difference is about factor 3! I have no idea what the cause of
this huge difference is. The main part of the code is shown below. The source
is actual C++ and uses just the dispatch library. Not every piece of source is
shown, but I can provide it if necessary.
Additional Info:
Synchronizing the access is achieved using dispatch_semaphore objects. Storing
a buffer into the buffers list may block if the buffers list has reached its
maximum number of buffers. Retrieving a buffer may block if there is no buffer
available.
After testing, it seems, the implementation is correct.
Class CFDataConstBufferschar is the type of the buffer list. Is has two
principal functions:
consume() and produce() which can be called concurrently.
consume() returns the next buffer in the list (FIFO). It may block until the
buffer list has one available.
produce() puts back a buffer. It may block, if the buffer's capacity (max
number of buffers) is reached.
Class CFDataConstBufferchar, the buffer class, is basically a thin wrapper
around a CFDataRef.
Class semaphore is a thin wrapper around a dispatch_semahore_t.
Below are two functions whose runtime duration is measured. Note that the
consumer part of the function ConcurrentProduceConsume() is written such that
it mimics the code produced by the compiler in the second function
ConcurrentProduceConsumeIter() which uses C++ Iterators - hence, it looks a bit
more complex than necessary. The code for the iterator isn't shown here, though.
The buffer size was set from 4KB to 32KB, incrementing in steps.
The buffers' list capacity (max number of hold buffers) was set to 1 to 8.
LLVM compiler, Xcode 4.02.
For no apparent reason ConcurrentProduceConsume() performs significantly faster
(about 2.5x) than ConcurrentProduceConsumeIter().
Is there a hidden cost for C++ instances in a block, for C++ exception
handlers, etc.?
Thanks for tips!
// Create a buffers instance with capacity C, then produce N buffers with
// BUFFER_SIZE bytes and fill them. Concurrently consume the buffers and
// iterate over the consumed buffer.
// Performs concurrently on two threads.
//
void ConcurrentProduceConsume(size_t C = 1, size_t N = 100)
{
typedef std::pairCFDataConstBufferchar, bool result_t;
// Create a buffers instance with at max C buffers:
CFDataConstBufferschar buffers(C);
CFDataConstBufferschar* buffersPtr = buffers;
const size_t TOTAL = BUFFER_SIZE * N;
// Get the global concurrent queue:
dispatch_queue_t queue =
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
// Create a group in order to sync the two threads:
dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, queue,
^{
unsigned long k = 0;
UInt8 data[BUFFER_SIZE];
for (int i = 0; i N; ++i) {
// fill the buffer:
for (int j = 0; j BUFFER_SIZE; ++j, ++k) {
data[j] = char(k);
}
CFDataRef d = CFDataCreate(NULL, data, sizeof(data));
CFDataConstBufferchar buffer = d;
CFRelease(d);
buffersPtr-produce(buffer);
}
// put EOF:
buffersPtr-produce(CFDataConstBufferchar());
});
dispatch_group_async(group, queue,
^{
const
sorting a pair of arrays
Hi, I have a pair of arrays (one of integers and one of strings) and I need to sort the one of integers from largest to smallest and then however it gets sorted I need to copy that sorting in my strings array since they are related. Any advice on what the best way to approach this is would be great since I don't have a lot of experience in sorting like this. Thanks! rc___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: sorting a pair of arrays
You want an object that holds both integer and string as properties. Put those objects in an array and sort that. On 28 Jun 2011, at 13:52, Rick C. wrote: Hi, I have a pair of arrays (one of integers and one of strings) and I need to sort the one of integers from largest to smallest and then however it gets sorted I need to copy that sorting in my strings array since they are related. Any advice on what the best way to approach this is would be great since I don't have a lot of experience in sorting like this. Thanks! rc___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/cocoadev%40mikeabdullah.net This email sent to cocoa...@mikeabdullah.net ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: sorting a pair of arrays
Hi Rick, It sounds to me like one way of looking at your data structures is as a NSDictionary with the first array as keys and the second as objects (values). If so, you could then sort the keys using - (NSArray *)keysSortedByValueUsingComparator:(NSComparator)cmptr , or one of the other sorting methods, and use the returned array to access the objects in turn. If the array-contaner is important for your code add the sorted objects to an array. NSArray, of course, also has a set of sorting methods, you could leverage to co-sort the strings in place. Mikkel On 28 Jun 2011, at 14:52, Rick C. wrote: Hi, I have a pair of arrays (one of integers and one of strings) and I need to sort the one of integers from largest to smallest and then however it gets sorted I need to copy that sorting in my strings array since they are related. Any advice on what the best way to approach this is would be great since I don't have a lot of experience in sorting like this. Thanks! rc___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/my.inputstream%40googlemail.com This email sent to my.inputstr...@googlemail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Reading Adobe Photoshop header, Obj-C
Was writing a program to create thumbnails using SIPS, GhostScript, ImageMagick. During testing I found I needed to read the header file of Adobe Photoshop native documents directly because Duotone image color mode simply wasn't returning the proper color mode (in a variety of programs). So I threw together this bit of code which works great for the first tag, but // References //http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/PhotoshopFileFormats.htm#50577409_pgfId-1055726 //http://www.adobe.com/content/dam/Adobe/en/devnet/photoshop/psir/ps_image_resources.pdf NSFileHandle *fileHandler = [NSFileHandle fileHandleForReadingAtPath:@/Users/kevin/Desktop/balloon.psd]; NSData *psdFileHeader = [NSData dataWithData:[fileHandler readDataOfLength:26]]; // read entire PSD header NSData *signature = [psdFileHeader subdataWithRange: NSMakeRange(0,4)]; NSData *version = [psdFileHeader subdataWithRange: NSMakeRange(4,2)]; NSData *reserved = [psdFileHeader subdataWithRange: NSMakeRange(6,6)]; NSLog(@Raw string is '%s' (length %d)\n, [signature bytes], [signature length]); NSLog(@Raw string is '%s' (length %d)\n, [version bytes], [version length]); NSLog(@Raw string is '%s' (length %d)\n, [reserved bytes], [reserved length]); As you can see from the output, the 'version' 'reserved' isn't being read at all. Must I coerce/parse something here? Much thanks... [Session started at 2011-06-28 09:14:31 -0400.] 2011-06-28 09:14:31.458 Read Standard Input[65929:10b] Raw string is '8BPS' (length 4) 2011-06-28 09:14:31.460 Read Standard Input[65929:10b] Raw string is '' (length 2) 2011-06-28 09:14:31.460 Read Standard Input[65929:10b] Raw string is '' (length 6) Kevin Muldoon e: caoimgh...@gmail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: dispatch_async Performance Issues
Hi Andreas, If I understand your post correctly, you are saying that you see a performance drop of 3x when using an iterator in your inner loop as opposed to using hand-written C code to do the iterating. Unfortunately you say you haven't actually posted the code relating to the iterator... but it seems to me that this is very likely to be the source of your problems! Your title states dispatch_async Performance Issues, but have you actually looked into whether you see the same problem in a single-threaded case that does not use dispatch_async? All I can suggest is that you examine the preprocessor output and even the generated assembly code with the aim of spotting any significant differences in the generated code in each case. It may well be that a function call is being generated as part of the iterator code, or something like that. Shark may help you pin down where the problem is, but you will probably need to have some level of appreciation of assembly code to be able to fully interpret the results for your optimized build. Unfortunately without the crucial part of your source code there's not a lot anyone else can do to help you in that respect... Hope that helps a bit Jonny___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: dispatch_async Performance Issues
... and more importantly I do not believe your code makes correct use of dispatch_group_async. Your first call adds a producer block to the global concurrent queue, which may start executing immediately. At some time soon afterwards you add a consumer block to the global concurrent queue, which again may start executing immediately - while the producer block is still in the process of producing. As far as I can see the code appears to have a number of major issues: 1. Theoretically your producer block may not have produced anything by the time your consumer block executes 2. What happens if your consumer block has processed all the currently-added blocks before the producer block has added the eof marker? 3. You have only one single consumer block, which means you will only have a single consumer thread running under Grand Central Dispatch, which rather defeats the purpose of using it at all! I think you may not have fully understood how GCD is intended to be used... 4. Are you sure that your mysterious and rather complicated-seeming CFDataConstBuffers class is sufficiently threadsafe for your producer to be adding to it at the same time as your consumer block is iterating through it? I am 99% sure that the explicit consumer code you wrote in ConcurrentProduceConsume is not threadsafe. Jonny.___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Assigning to property with 'readonly' atribute not allowed
On 27 Jun 2011, at 9:52 PM, Fernando Aureliano wrote:
- (AQGridViewCell *) gridView: (AQGridView *)inGridView cellForItemAtIndex:
(NSUInteger) index;
{
MagazineCell *cell = (MagazineCell *)[inGridView
dequeueReusableCellWithIdentifier:@cell];
if (!cell) {
cell = [MagazineCell cell];
*cell.reuseIdentifier = @cell;*
//Assigning to property with 'readonly' atribute not allowed
}
cell.backgroundColor = [UIColor clearColor];
cell.selectionStyle = AQGridViewCellSelectionStyleGlow;
cell.edicaoLabel.text = [[edicoesArray objectAtIndex:index] name];
cell.dataLabel.text = [[edicoesArray objectAtIndex:index] name];
return cell;
}
I tried to do this on head file
@property(nonatomic, readwrite) NSString * reuseIdentifier;
I also tried
@property(nonatomic, assign) NSString * reuseIdentifier;
But still no work.
In what way was the reply you got yesterday not satisfactory?
The class seems to be modeled on UITableViewCell, in which assignment to the
reuse identifier is illegal.
A glance at the class on GitHub suggests the reason: The identifier is intended
as a key into an NSMutableDictionary. In general, changing the identifier would
require changing the placement of the cell in the dictionary. AQGridViewCell
has no reference back to its container, so the change is impossible. Changing
reuseIdentifier would break AQGridView.
Redeclaring reuseIdentifier won't change an assignment that can't work into one
that can. All it would do is silence the compiler and leave your app to crash.
Changing the attribute to assign is a particularly bad idea when the intended
behavior is copy. Review the memory-management guide to understand why.
I assume you have control over class MagazineCell, and can initialize it as you
please. Why can't you call [super initWithFrame: CGRectZero reuseIdentifier:
@cell] in its initializer?
— F
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Help with relationship objects
I need a little guidance. Did I properly add a relationship object? I don't
know what's normal in this scenario.
I referred to here:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/Articles/cdUsingMOs.html
I have an entity called SRNoteEntity which has a to-many relationship with
SRTodoEntity in a mutableSet called todos. When I do the following:
[thisNote addTodosObject:todoItem];
I get the below. Notice the new SRTodoEntity is properly in the todos
relationship but there's also a reference to it outside of the SRNoteEntity.
Intuitively, I would think there should be only one reference to it inside
SRNoteEntity.This is my confusion. Why is it reference twice? How can I
prevent that from happening if this isn't normal?
po [[self managedObjectContext] registeredObjects]
{(
Note uid:330961758011065
creationDate:2009-09-05 13:21:54 -0400
modificationDate:2009-09-06 12:41:02 -0400
todos:Relationship objects for {(
SRTodoEntity: 0x200483d80 (entity: SRTodoEntity; id: 0x2004121e0
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRTodoEntity/p1 ; data: {
note = 0x2002c4e60
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRNoteEntity/p1;
todoViewData = nil;
})
)} on 0x200448360
noteData:538
SRTodoEntity: 0x200483d80 (entity: SRTodoEntity; id: 0x2004121e0
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRTodoEntity/p1 ; data: {
note = 0x2002c4e60
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRNoteEntity/p1;
todoViewData = nil;
})
)}
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Re: sorting a pair of arrays
Mikkel Islay wrote:
It sounds to me like one way of looking at your data structures is as a
NSDictionary with the first array as keys and the second as objects (values).
Which fails the if there's any possibility that the items in the first array
aren't unique. Better two have an array of dictionaries where each dictionary
holds a respective pair from the current two arrays as their own objects
{
myInt - 1
myString - some string
}
Then a typical use of either sort descriptors or a comparison proc.
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Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 6:23 AM, Kevin Muldoon wrote: As you can see from the output, the 'version' 'reserved' isn't being read at all. Must I coerce/parse something here? Much thanks… I’m not familiar with the PSD format, but aren’t ‘version’ and ‘reserved’ binary? You’re printing them as C strings. Assuming ‘version’ is a 16-bit big-endian integer, you could read it like this: const uint8_t* bytes = [signature bytes]; uint16_t version = *(const uint16_t*)(bytes + 2); version = NSSwapBigShortToHost(version); Another way (that I often use) is to define a C struct that matches the fields and layout of the header, then cast the bytes to a pointer to that struct and read the fields. It makes your code look a lot cleaner, but you have to be careful to (a) make sure the compiler packs the struct fields properly, and (b) you byte-swap all integer/float fields appropriately. —Jens smime.p7s Description: S/MIME cryptographic signature ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: sorting a pair of arrays
On Jun 28, 2011, at 5:52 AM, Rick C. wrote: I have a pair of arrays (one of integers and one of strings) and I need to sort the one of integers from largest to smallest and then however it gets sorted I need to copy that sorting in my strings array since they are related. Any advice on what the best way to approach this is would be great since I don't have a lot of experience in sorting like this. Thanks! Another way to do this, besides what’s been suggested, is to make a new numeric array that maps old indexes to sorted indexes. Start it out as the identity (a[i] = i), then sort it using a compare function that compares the ints mapped into your original int array. Then use the sorted index mapping to renumber your original arrays. —Jens smime.p7s Description: S/MIME cryptographic signature ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
Hey Jens, I suppose the trouble here is that I'm familiar with Objective-C code and not so familiar with its parent, C. On Jun 28, 2011, at 1:00 PM, Jens Alfke wrote: On Jun 28, 2011, at 6:23 AM, Kevin Muldoon wrote: As you can see from the output, the 'version' 'reserved' isn't being read at all. Must I coerce/parse something here? Much thanks… I’m not familiar with the PSD format, but aren’t ‘version’ and ‘reserved’ binary? You’re printing them as C strings. Assuming ‘version’ is a 16-bit big-endian integer, you could read it like this: const uint8_t* bytes = [signature bytes]; uint16_t version = *(const uint16_t*)(bytes + 2); version = NSSwapBigShortToHost(version); Another way (that I often use) is to define a C struct that matches the fields and layout of the header, then cast the bytes to a pointer to that struct and read the fields. It makes your code look a lot cleaner, but you have to be careful to (a) make sure the compiler packs the struct fields properly, and (b) you byte-swap all integer/float fields appropriately. —Jens Kevin Muldoon e: caoimgh...@gmail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 10:11 AM, Kevin Muldoon wrote: I suppose the trouble here is that I'm familiar with Objective-C code and not so familiar with its parent, C. Yeah, unfortunately Objective-C does not absolve you of having to know C. With where you’re going, I’d suggest cracking open Kernighan Ritchie or some other good C book. (It’s a shame Cocoa doesn’t have more powerful stream APIs, or some equivalent of Perl/PHP/Ruby’s ‘unpack’ function, that would let you do this kind of stuff without needing to do pointer grunge. For some reason streams have always been a primary Achilles’ heel of Cocoa. I’ve been coding in it for ten years and I still never use NSFileHandle — if I have to stream data to/from files I just drop down to ANSI C or POSIX I/O calls.) —Jens smime.p7s Description: S/MIME cryptographic signature ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: dispatch_async Performance Issues
On Jun 28, 2011, at 3:53 PM, Jonathan Taylor wrote:
Hi Jonathan,
Thank you very much for taking the time to look at it.
Hi Andreas,
If I understand your post correctly, you are saying that you see a
performance drop of 3x when using an iterator in your inner loop as opposed
to using hand-written C code to do the iterating.
Yes, at least that was my former assumption.
In the meantime however, I found one (surprising) cause of the performance
issue. After making the versions *more* equivalent the issue become apparent.
I restructured the second version (using the C++ iterators) and will discuss
this in more detail. The culprit is in the consumer part as follows:
New restructured code:
...
#if defined (USE_FUTURE)
__block size_t sum = 0;
__block size_t total = 0;
#endif
dispatch_async(queue,
^{
CFDataConstBuffers_iteratorchar eof;
CFDataConstBuffers_iteratorchar iter(*buffersPtr);
size_t sum_ = 0;
size_t total_ = 0;
while (iter != eof)
{
sum_ += *iter;
++iter;
++total_;
}
#if defined (USE_FUTURE)
sum = sum_;
total = total_;
#endif
semPtr-signal();
});
...
The difference compared to the former code provided in the previous mail is now
1) The C++ instances, that is the iterators, are defined locally within the
block.
2) The Future (that is the result of the operation) is conditional compiled
in or out, in order to test its impact.
Here, the __block modifier is used for the Future variables sum and
total.
When using pointers within the block accessing the outside variables, the
performance does not differ, but using __block may be more correct.
Note, that I access the variables sum and total only once at the end of the
block code. This has a reason, which I will explain below.
As mentioned, the conditional #if define (USE_FUTURE) tests its impact on
performance.
If USE_FUTURE is defined, the performance drops dramatically!
The same happens, if there are pointer variables which access variables defined
outside the block.
The performance drops even more if I would use the __block variables sum and
total directly when incrementing, e.g.:
while (iter != eof)
{
sum += *iter;
++iter;
++total;
}
Even when I access the Future sum and total only once in the block, the
performance penalty is significant.
Unfortunately you say you haven't actually posted the code relating to the
iterator... but it seems to me that this is very likely to be the source of
your problems!
OK, appended the source code. :)
These are three files, and a lot for this mail.
But I guess, this is not the cause of the issue.
Your title states dispatch_async Performance Issues, but have you actually
looked into whether you see the same problem in a single-threaded case that
does not use dispatch_async?
I haven't *exactly* done this one, but I have a lot of other test cases (see
below).
All I can suggest is that you examine the preprocessor output and even the
generated assembly code with the aim of spotting any significant differences
in the generated code in each case. It may well be that a function call is
being generated as part of the iterator code, or something like that. Shark
may help you pin down where the problem is, but you will probably need to
have some level of appreciation of assembly code to be able to fully
interpret the results for your optimized build.
I examined the assembly and from the looks I couldn't find any hints. Both
versions looked quite similar. My guess is, it is some synchronization
primitive like a spin lock.
After modifying the direct implemented and C++ Iterator versions, both run
now similar if no future is used. If a future is used, for some reason, the
runtime drops much more for the C++ Iterator version than the code that mimics
the behavior.
But, considering my original goal, performance is a bit slow, that is, not
faster then a very primitive implementation which uses one thread, allocates
NSData buffers, and adds them to a NSMutableData object which is then processed
(see Classic bench). This is a bit disappointing. Guess the overhead for
dispatch is still high. Here are some results of my bench marks (note that in
single threaded approaches the future has no effect since there is none):
CFDataBuffers Benchmark
Using Future: No
Data size: 131072KB, Buffer size: 8192, N = 16384, C = 2
[SimpleProduceConsume1]:Elapsed time: 299.028ms
[SimpleProduceConsume2]:Elapsed time: 125.744ms
[Classic]: Elapsed time: 218.383ms
[ConcurrentProduceConsume1]:Elapsed time: 123.748ms
[ConcurrentProduceConsume2]:Elapsed time: 271.387ms
[ConcurrentProduceConsumeIter]: Elapsed time: 265.175ms
Re: dispatch_async Performance Issues
On Jun 28, 2011, at 4:07 PM, Jonathan Taylor wrote: ... and more importantly I do not believe your code makes correct use of dispatch_group_async. Your first call adds a producer block to the global concurrent queue, which may start executing immediately. At some time soon afterwards you add a consumer block to the global concurrent queue, which again may start executing immediately - while the producer block is still in the process of producing. As far as I can see the code appears to have a number of major issues: 1. Theoretically your producer block may not have produced anything by the time your consumer block executes The consumer thread may block until a buffer is available. This happens in member function consume() of the buffer list. 2. What happens if your consumer block has processed all the currently-added blocks before the producer block has added the eof marker? The consumer block loops until a buffer is available, or until an timeout occurs. This happens in member consume(). An empty buffer signals EOF. 3. You have only one single consumer block, which means you will only have a single consumer thread running under Grand Central Dispatch, which rather defeats the purpose of using it at all! I think you may not have fully understood how GCD is intended to be used... I know this. But there is no easy way around, due to this: the buffers represent a contiguous stream of data. The consumer thread is used to execute a parser. The parser can not simply stop and then continue with a new chunk of data. The parser's state is represented in the execution stack. So, the parser may block when it iterates over the data buffers and thus safes its state that way. I know that this is not the optimal way to use GCD. But at least I get semaphores which do not trap into the kernel that often, and thread switching shall be faster as well. The original goals for this approach is: Reduce memory foot print. The buffers list maximum number of buffers is limited. Increase overall performance due to simultaneously downloading data and parsing. Scaleability . No need to safe the stream to an intermediate file on disk before parsing. Avoid copying of data completely. 4. Are you sure that your mysterious and rather complicated-seeming CFDataConstBuffers class :) is sufficiently threadsafe for your producer to be adding to it at the same time as your consumer block is iterating through it? I am 99% sure that the explicit consumer code you wrote in ConcurrentProduceConsume is not threadsafe. I hope it is. But there may be subtle caveats which can in certain circumstances reduce performance due to frequent context switches. I would avoid it if I would know IF and when this can happen ;) The source is available (see link previous mail). Would you mind taking a look at it? But be warned: this is C++ code. Thanks in advance! Andreas Jonny. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
No problem at all. I'll pick up Kernighan Ritchie. Thanks for reply. On Jun 28, 2011, at 1:17 PM, Jens Alfke wrote: On Jun 28, 2011, at 10:11 AM, Kevin Muldoon wrote: I suppose the trouble here is that I'm familiar with Objective-C code and not so familiar with its parent, C. Yeah, unfortunately Objective-C does not absolve you of having to know C. With where you’re going, I’d suggest cracking open Kernighan Ritchie or some other good C book. (It’s a shame Cocoa doesn’t have more powerful stream APIs, or some equivalent of Perl/PHP/Ruby’s ‘unpack’ function, that would let you do this kind of stuff without needing to do pointer grunge. For some reason streams have always been a primary Achilles’ heel of Cocoa. I’ve been coding in it for ten years and I still never use NSFileHandle — if I have to stream data to/from files I just drop down to ANSI C or POSIX I/O calls.) —Jens Kevin Muldoon e: caoimgh...@gmail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Help with relationship objects
On Jun 28, 2011, at 08:40, Brad Stone wrote:
I get the below. Notice the new SRTodoEntity is properly in the todos
relationship but there's also a reference to it outside of the SRNoteEntity.
Intuitively, I would think there should be only one reference to it inside
SRNoteEntity.This is my confusion. Why is it reference twice? How can I
prevent that from happening if this isn't normal?
po [[self managedObjectContext] registeredObjects]
{(
Note uid:330961758011065
creationDate:2009-09-05 13:21:54 -0400
modificationDate:2009-09-06 12:41:02 -0400
todos:Relationship objects for {(
SRTodoEntity: 0x200483d80 (entity: SRTodoEntity; id: 0x2004121e0
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRTodoEntity/p1 ; data: {
note = 0x2002c4e60
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRNoteEntity/p1;
todoViewData = nil;
})
)} on 0x200448360
noteData:538
SRTodoEntity: 0x200483d80 (entity: SRTodoEntity; id: 0x2004121e0
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRTodoEntity/p1 ; data: {
note = 0x2002c4e60
x-coredata://614245CF-F03E-4F43-9D7F-98CDCB2899FA/SRNoteEntity/p1;
todoViewData = nil;
})
)}
You've kinda got hold of the wrong end of this. Core Data is an object graph,
certainly, and any pointer to a managed object is a reference to the object.
There are references to these objects all over your code -- every stack
variable pointer is a reference. In the above example, a reference to the Todo
object exists inside the set of references that represents Note's relationship
to its Todo's. That makes it a really important reference, but it's certainly
never the only one.
By sending a 'registeredObjects' message to the managedObjectContext (which is
*not* an object in the object graph), you've asked it to construct a collection
(a set, as it happens) of references to Core Data objects it knows about.
There's no *relationship* from the MOC to the managed objects, it's just the
MOC's job to know what managed objects are currently in memory.
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Re: Reading Adobe Photoshop header, Obj-C
On 28 Jun 2011 10:00:51 -0700, Jens Alfke j...@mooseyard.com posited: Assuming Œversion‚ is a 16-bit big-endian integer, you could read it like this: The htons() and ntohs() C calls go from host-native integer (short) format to network format (big-endian), and from network format back to host-native short ints. There are also long versions of these calls. These calls are also implemented to provide correct operations on hosts systems that are little- and big-endian; they're portable across platforms. If you have to do more of this (at the C layer), then you might consider using the xdr external data representation calls, too. And FWIW, going the other way (from knowing C to learning Objective C) can be fun, too. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: sorting a pair of arrays
On 28 Jun 2011, at 18:40, Gregory Weston wrote: Which fails the if there's any possibility that the items in the first array aren't unique. Better two have an array of dictionaries where each dictionary holds a respective pair from the current two arrays as their own objects] Granted, but in that case you might also consolidate objects for identical keys, to retain the natural index and easily inspect related objects. Mikkel___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: dispatch_async Performance Issues
In the meantime however, I found one (surprising) cause of the performance issue. After making the versions *more* equivalent the issue become apparent. I restructured the second version (using the C++ iterators) and will discuss this in more detail. The culprit is in the consumer part as follows: New restructured code: [...] The difference compared to the former code provided in the previous mail is now 1) The C++ instances, that is the iterators, are defined locally within the block. 2) The Future (that is the result of the operation) is conditional compiled in or out, in order to test its impact. Here, the __block modifier is used for the Future variables sum and total. When using pointers within the block accessing the outside variables, the performance does not differ, but using __block may be more correct. Ah - now then! I will take a very strong guess as to what is happening there (I've done it myself, and seen it done by plenty of others! [*]). In the case where you do NOT define USE_FUTURE, your consumer thread as written in your email does not make any use of the variables sum_ and total_. Hence the compiler is entirely justified in optimizing out those variables entirely! It will still have to check the iterator against eof, and may have to dereference the iterator[**], but it does not need to update the sum_ or total_ variables. It may well be that there is still a deeper performance issue with your original code, and I'm happy to have another look at that when I have a chance. I suggest you deal with this issue first, though, as it appears to be introducing misleading discrepancies in the execution times you're using for comparison. As I say, it's quite a common issue when you start stripping down code with the aim of doing minimal performance comparisons. The easiest solution is either to printf the results at the end (which forces the compiler to actually evaluate them!), or alternatively do the sort of thing you're doing when USE_FUTURE is defined - writing to a shadow variable at the end. If you declare your shadow variable as volatile then the compiler is forced to write the result and is not permitted to optimize everything out. Hope that helps, even if it may not deal with your original problem yet. Apologies that my first round of guesses were wrong - I'm pretty sure about this one though :) Jonny [**] Completely unrelated to this thread, but see this rather extreme example where the claimed performance had to be reduced by a factor of twelve due to this problem! http://www.ibm.com/developerworks/forums/thread.jspa?threadID=226415 [*] I ~think~ ... because this involves a memory access, which is strictly speaking a side effect in itself. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On 28.06.2011, at 15:23, Kevin Muldoon wrote:
Was writing a program to create thumbnails using SIPS, GhostScript,
ImageMagick. During testing I found I needed to read the header file of Adobe
Photoshop native documents directly because Duotone image color mode simply
wasn't returning the proper color mode (in a variety of programs).
So I threw together this bit of code which works great for the first tag,
but
// References
//http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/PhotoshopFileFormats.htm#50577409_pgfId-1055726
//http://www.adobe.com/content/dam/Adobe/en/devnet/photoshop/psir/ps_image_resources.pdf
NSFileHandle *fileHandler = [NSFileHandle
fileHandleForReadingAtPath:@/Users/kevin/Desktop/balloon.psd];
NSData *psdFileHeader = [NSData dataWithData:[fileHandler
readDataOfLength:26]]; // read entire PSD header
NSData *signature = [psdFileHeader subdataWithRange: NSMakeRange(0,4)];
NSData *version = [psdFileHeader subdataWithRange: NSMakeRange(4,2)];
NSData *reserved = [psdFileHeader subdataWithRange: NSMakeRange(6,6)];
You're doing the worst case for performancewise.
The usual way would be to define a struct
#pragma pack (push, 2)
typedef struct {
uint32_t psdMagic;
uint16_t version;
uint16_t reserved1;
uint32_t reserved2;
} PSDHeader;
and use it with code like:
NSData * psdHdrData = [NSData dataWithData:[fileHandler
readDataOfLength:sizeof( PSDHeader )]]; // read entire PSD header
PSDHeader *header = (psdHeader *) [psdHdrData bytes];
psdMagic = CFEndianBToN( header-psdMagic );
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Re: Reading Adobe Photoshop header, Obj-C
On 28.06.2011, at 21:37, Charles Srstka wrote: On Jun 28, 2011, at 12:00 PM, Jens Alfke wrote: Another way (that I often use) is to define a C struct that matches the fields and layout of the header, then cast the bytes to a pointer to that struct and read the fields. It makes your code look a lot cleaner, but you have to be careful to (a) make sure the compiler packs the struct fields properly, and (b) you byte-swap all integer/float fields appropriately. It’s my understanding that reading/writing a struct directly to/from a file is considered poor practice, because of the two things you mentioned: endian issues, and the fact that you don’t know how the compiler will align the fields — and even if you test that, you don’t know that it’s not going to change in some future version of clang or gcc, or that Apple’s not going to switch to a new architecture or something in which the compilers will emit different output. - the endian issue you'll have to deal with anyway - regarding struct alignment: the 80ies file format had tons of of serialized struct data which usually better end up in a struct. Well, streamed reading has bad performance, so you'd not want to use it in image (or movie) manipulation code. Streamed reading just to put it back into a struct is another anti-pattern. The don't is to use binary structs for new defined protocols for transfer, for the given reasons. Regards, Tom_E ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Menu Title Icon in Cocoa
Hi, I'd like to know if there is a way of inserting an icon instead of a menu title in the menu bar. I'm not speaking of the system status bar, but simply of my application's menus. In Carbon, I used to use SetMenuTitleIcon(): so the question is is there an equivalent of SetMenuTitleIcon in Cocoa ? Thanks for any clue on this matter, I can't find anything on the web, Bernard ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On 28.06.2011, at 21:57, Thomas Engelmeier wrote: On 28.06.2011, at 21:37, Charles Srstka wrote: On Jun 28, 2011, at 12:00 PM, Jens Alfke wrote: Another way (that I often use) is to define a C struct that matches the fields and layout of the header, then cast the bytes to a pointer to that struct and read the fields. It makes your code look a lot cleaner, but you have to be careful to (a) make sure the compiler packs the struct fields properly, and (b) you byte-swap all integer/float fields appropriately. It’s my understanding that reading/writing a struct directly to/from a file is considered poor practice, because of the two things you mentioned: endian issues, and the fact that you don’t know how the compiler will align the fields — and even if you test that, you don’t know that it’s not going to change in some future version of clang or gcc, or that Apple’s not going to switch to a new architecture or something in which the compilers will emit different output. - the endian issue you'll have to deal with anyway - regarding struct alignment: the 80ies file format had tons of of serialized struct data which usually better end up in a struct. Well, streamed reading has bad performance, so you'd not want to use it in image (or movie) manipulation code. P.S.: unless the structs have variable length data in the middle, i.e. can not be read in one read anyway. IIRC the PS structures are not organized that way, though. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Custom NSCell and Bindings
On Fri, 24 Jun 2011 09:33:38 -0400, Carter R. Harrison said: It's a pretty typical situation. I've got my model objects stored in an NSSet. An NSArrayController that is bound to the NSSet. And then an NSTableView with one NSTableColumn bound to the arrangedObjects.name property of the NSArrayController. It works great. Now I've introduced a custom NSCell object into the NSTableView. The custom cell displays a title, a subtitle, and a status image - all of which I want to be able to bind to 3 separate properties of the model object. How do I do this? Right now with the 'value' binding bound to the arrangedObjects.name property, on the title of my custom cell updates when the model updates. If the subtitle or status update in the model object the cell does not update. Any help is greatly appreciated. Basically, you can't. :( The table column has only one value binding, so can only be bound to one thing, not many. You could change your model to have one property that is an amalgamation of your title, subtitle, and image and bind to that. -- Sean McBride, B. Eng s...@rogue-research.com Rogue Researchwww.rogue-research.com Mac Software Developer Montréal, Québec, Canada ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Custom NSCell and Bindings
Hello Carter.
Right now I can't remember the name of the example.
Its a little tricky but its do-able.
your MO subclass must do something like:
-(NSDictionary *)userDictionary{
return [self dictionaryWithValuesForKeys:[NSArray
arrayWithObjects:@firstName,@lastName,@avatar,@title,nil]];
}
+(NSSet *)keyPathsForValuesAffectingUserDictionary{
return [NSSet
setWithObjects:@firstName,@lastName,@avatar,@title,nil];
}
which the right properties.
then in the xib bind the value of the tablecolum to
arrangedObjects.userDictionary.
then subclass NSCell, on the awakeFromNib of the controller that contains the
tableview tell the TableColum to set its dataCell as the instance of my custom
cell, (of course I have to initialize my cell before that particular line).
then in my cell what I do is:
//
//Draw the cell that contains the name of the user andits picutre
//This methods tales the objectValue which is a NSDictionary, all this is done
bia bindings,
//the use entoty has a property NSDictionary keysDictionary which will return
all the keys of its propertioes with its corresponding values see @ User.m
//
-(void)drawWithFrame:(NSRect)cellFrame inView:(NSView *)controlView{
NSDictionary * cellValues = [self objectValue];
NSString * firstName = [cellValues valueForKey:@firstName];
NSString * lastName = [cellValues valueForKey:@lastName];
NSString * completeName = [NSString stringWithFormat:@%@
%@,firstName,lastName];
NSPoint textPoint;
NSDictionary *textAttributes;
NSColor * fontColor;
fontColor = [self isHighlighted]?[NSColor whiteColor]:[NSColor
blackColor];
textAttributes = [NSDictionary dictionaryWithObjectsAndKeys: fontColor,
NSForegroundColorAttributeName, [NSFont fontWithName:@Optima
size:(CGFloat)13.0], NSFontAttributeName, nil];
NSSize nameSize = [completeName sizeWithAttributes:textAttributes];
textPoint.x = cellFrame.origin.x + 5.0f;
textPoint.y = cellFrame.origin.y +(cellFrame.size.height -
nameSize.height)/2.0f - 5.0f ;
NSRect rectOfDraw = NSMakeRect(textPoint.x,
textPoint.y,cellFrame.size.width - 50.0f,nameSize.height);
[completeName drawWithRect:rectOfDraw
options:NSStringDrawingTruncatesLastVisibleLine|NSStringDrawingUsesLineFragmentOrigin
attributes:textAttributes];
//Getting the Avatr Value
NSData * avatar = [cellValues valueForKey:@avatar];
NSImage * avatarImage = [[[NSImage alloc] initWithData:avatar]
autorelease];//[NSImage imageNamed:@NoAvatar];
[[NSGraphicsContext currentContext] saveGraphicsState];
CGFloat yOffset = cellFrame.origin.y;
//Checking if the controll view its flipped or no
//Most probably it is.
//then create an affine tarsnfor and translate its coordinates
if ([controlView isFlipped]) {
NSAffineTransform* xform = [NSAffineTransform transform];
[xform translateXBy:0.0 yBy: cellFrame.size.height];
[xform scaleXBy:1.0 yBy:-1.0];
[xform concat];
yOffset = 0-cellFrame.origin.y;
}
//Create and interpolation
//medium its ok, due we don't need to show a high resolutiuon thumbnail
NSImageInterpolation interpolation = [[NSGraphicsContext
currentContext] imageInterpolation];
[[NSGraphicsContext currentContext] setImageInterpolation:
NSImageInterpolationMedium];
//configure the image drawrect and size and pritn in on screen
if(avatarImage != nil){
NSRect imageRect ;
imageRect = NSZeroRect;
imageRect.size = [avatarImage size];
NSRect drawingRect;
drawingRect.origin.x = cellFrame.size.width - 40.0f;
drawingRect.origin.y = yOffset + 2.0;
drawingRect.size = NSMakeSize(37.0f, 37.0f);
[avatarImage drawInRect:drawingRect
fromRect:imageRect
operation:NSCompositeSourceOver
fraction:0.9];
}
[[NSGraphicsContext currentContext] setImageInterpolation:
interpolation];
[[NSGraphicsContext currentContext] restoreGraphicsState];
}
basically is jut taking the values from the cell objectvalue which is a
dictionary and then is just set up of the things inside. So it displays
correctly the name, the last name and the image of the user, in my case.
Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 2:57 PM, Thomas Engelmeier wrote: - the endian issue you'll have to deal with anyway Yes, that was the point. You already have to go through the struct member by member and fix the endians anyway, so reading the whole thing in as one block of data won’t actually make your code look that much “cleaner. - regarding struct alignment: the 80ies file format had tons of of serialized struct data which usually better end up in a struct. Well, streamed reading has bad performance, so you'd not want to use it in image (or movie) manipulation code. Streamed reading just to put it back into a struct is another anti-pattern. The don't is to use binary structs for new defined protocols for transfer, for the given reasons. I am not sure that whatever performance improvement is to be gained by doing this is worth the inherent danger in doing this. Certainly I don’t think it’s a good idea to recommend this to people who are not familiar with the issues involved. Reading/writing structs directly into and out of files seems like something that should never be done unless you are very familiar with the way the compiler works. By all means, you can read the whole header into a buffer at once to cut the fread calls down to one, but I’d still move the values into the struct member by member (and of course, you’re going to be doing this anyway, as even if you read the data directly into the struct, you’re still going to have to go through it and assign bit-swapped values to the struct — member by member). FWIW, Apple also recommends against loading structs directly into and out of raw data (here referring to NSData objects, but it’s the same principle) for the same reason — you’re essentially relying on undocumented behavior on the part of the compiler. http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Archiving/Articles/codingctypes.html#//apple_ref/doc/uid/20001294-96941 And of course, we don’t even know if performance is a concern to the OP or not. This could very likely all be a case of premature optimization, especially if creating a whole NSData object for each member is acceptable to him, as in the code originally posted. Charles___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On 28 Jun 2011, at 18:00, Jens Alfke wrote: Another way (that I often use) is to define a C struct that matches the fields and layout of the header, then cast the bytes to a pointer to that struct and read the fields. It makes your code look a lot cleaner, but you have to be careful to (a) make sure the compiler packs the struct fields properly You can do this with __attribute__((packed)) - see http://developer.apple.com/library/mac/#documentation/DeveloperTools/gcc-4.2.1/gcc/Type-Attributes.html. Be aware that __attribute__((packed)) is a GCC extension though, so it may not be supported by other compilers. Francis ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Menu Title Icon in Cocoa
On Jun 28, 2011, at 10:00 PM, Bernard Desgraupes wrote: Hi, I'd like to know if there is a way of inserting an icon instead of a menu title in the menu bar. I'm not speaking of the system status bar, but simply of my application's menus. In Carbon, I used to use SetMenuTitleIcon(): so the question is is there an equivalent of SetMenuTitleIcon in Cocoa ? Thanks for any clue on this matter, I can't find anything on the web, Bernard Sure. The title of each NSMenu is in fact a NSMenuItem and it has a -setImage: method that you can call. You can also do this in Interface Builder by selecting the menu, selects its underlying NSMenuItem and then choose which image you want directly in the inspector. Marcus smime.p7s Description: S/MIME cryptographic signature ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
Kevin, As others have suggested you probably want to step down to more basic C coding to handle this task. You can just use C library functions to read data from the file: fopen(), fseek(), fread(), fgetc(), fclose() etc. as discussed in Kernighan and Ritchie. As far as big endian, little endian issues, most image files use the convention 'MM' for big endian or 'II' for little endian somewhere in the first few bytes of the file. You then need to load the data accordingly. For example looking at a Photoshop Elements file, I see MM' (two ASCII characters) as the first two bytes of the file, announcing that the file is big endian. A tool that may be helpful for you in looking at file data directly is a Hex Editor. I use HexEdit which is freeware. Beware-- a Hex Editor is a sharp tool, you can open any file on your system and modify it. Jim Merkel ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 6:18 PM, James Merkel wrote: Kevin, As others have suggested you probably want to step down to more basic C coding to handle this task. You can just use C library functions to read data from the file: fopen(), fseek(), fread(), fgetc(), fclose() etc. as discussed in Kernighan and Ritchie. As far as big endian, little endian issues, most image files use the convention 'MM' for big endian or 'II' for little endian somewhere in the first few bytes of the file. You then need to load the data accordingly. For example looking at a Photoshop Elements file, I see MM' (two ASCII characters) as the first two bytes of the file, announcing that the file is big endian. A tool that may be helpful for you in looking at file data directly is a Hex Editor. I use HexEdit which is freeware. Beware-- a Hex Editor is a sharp tool, you can open any file on your system and modify it. Jim Merkel Synalyzeit is a free hex editor that's fabulous. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/jjoyce%40apple.com This email sent to jjo...@apple.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 4:35 PM, John Joyce wrote: On Jun 28, 2011, at 6:18 PM, James Merkel wrote: Kevin, As others have suggested you probably want to step down to more basic C coding to handle this task. You can just use C library functions to read data from the file: fopen(), fseek(), fread(), fgetc(), fclose() etc. as discussed in Kernighan and Ritchie. As far as big endian, little endian issues, most image files use the convention 'MM' for big endian or 'II' for little endian somewhere in the first few bytes of the file. You then need to load the data accordingly. For example looking at a Photoshop Elements file, I see MM' (two ASCII characters) as the first two bytes of the file, announcing that the file is big endian. A tool that may be helpful for you in looking at file data directly is a Hex Editor. I use HexEdit which is freeware. Beware-- a Hex Editor is a sharp tool, you can open any file on your system and modify it. Jim Merkel Synalyzeit is a free hex editor that's fabulous. Thanks, I'll take a look at that. HexEdit is getting a little dated. Jim Merkel ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 4:53 PM, James Merkel wrote: Synalyzeit is a free hex editor that's fabulous. Thanks, I'll take a look at that. HexEdit is getting a little dated. Hex Fiend (open source) is nice too http://ridiculousfish.com/hexfiend/ —Jens smime.p7s Description: S/MIME cryptographic signature ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Reading Adobe Photoshop header, Obj-C
On Jun 28, 2011, at 7:14 PM, Jens Alfke wrote: On Jun 28, 2011, at 4:53 PM, James Merkel wrote: Synalyzeit is a free hex editor that's fabulous. Thanks, I'll take a look at that. HexEdit is getting a little dated. Hex Fiend (open source) is nice too http://ridiculousfish.com/hexfiend/ —Jens hex fiend is pretty cool too. embeddable no less!___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: sorting a pair of arrays
Thanks for all of the insight! I'll be trying out these suggestions and if I have any further questions I'll post back... rc On Jun 29, 2011, at 2:06 AM, Mikkel Islay wrote: On 28 Jun 2011, at 18:40, Gregory Weston wrote: Which fails the if there's any possibility that the items in the first array aren't unique. Better two have an array of dictionaries where each dictionary holds a respective pair from the current two arrays as their own objects] Granted, but in that case you might also consolidate objects for identical keys, to retain the natural index and easily inspect related objects. Mikkel___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/rickcorteza%40gmail.com This email sent to rickcort...@gmail.com ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Problem with setNeedsLayout and layoutSubviews in UIScrollView
Em 27/06/2011, às 13:56, David Duncan escreveu: The problem is that a UIDeviceOrientaiton also includes Unknown, FaceUp and FaceDown orientations. Thus !Landscape means Portrait or one of those (ditto for !Portrait). A large portion of the time, your likely holding the device in FaceUp orientation as far as UIDeviceOrientation is concerned, and thus failing your Landscape check. All right, I didn't know about FaceUp and FaceDow. Now makes sense So, if scroll view layout during scroll, I cannot do this resizing in layoutSubview, and should do this in shouldAutorotateToInterfaceOrientation method in my controller? No, you would use -willAnimateAutorotationToInterfaceOrientation:duration: to do your layout. But at a higher level, why layout based on orientation in the first place? Unless you have specific elements that should not appear in one orientation or another (which doesn't seem to be the case from your code) why not just layout based on the size of the containing view? You can locally determine if it is a portrait or landscape view by comparing width height in many cases. I'm doing this because autoresizingMask wasn't working correctly. I have in this scroll view (planed to be visualized mainly in portrait, but also in landscape) a view that width height. If I put just UIVireAutoResiningFlexibleHeight | UIVireAutoResiningFlexibleWidth, the view get the right size in horizontal , but is compressed in vertical (as when I put in landscape, the proportion of dimensions change). And if I used just UIVireAutoResiningFlexibleWidth, the subcomponents get not proportionally re dimensioned. I have implemented in shouldAutorotateToInterfaceOrientation and it worked, but I will change to willAnimateToInterfaceOrientation:duration: as you proposed. Thank you -- David Duncan ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
how to get viewable text position after scroll a UITextView
I have a UITextView and a slide control. The text view has a long content to read. I need textview can interact with slide control. Now I can drag slide to move text view text to corresponding percentage by calculating position of slide control. I want to move slide indicator position to corresponding position by scroll text view too. But how I can get current viewable text position? Then I can calculate its percentage to move slide. BTW, I can use an inherit UITextView to catch event now. Thanks, hufey ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
