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Re: archiving report
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Re: archiving report


  • Subject: Re: archiving report
  • From: Sean McBride <email@hidden>
  • Date: Tue, 26 Feb 2013 13:11:39 -0500
  • Organization: Rogue Research Inc.

On Wed, 27 Feb 2013 00:47:35 +0700, Gerriet M. Denkmann said:

>2. NSKeyedArchiver seems to be ok.

One problem I know of with NSKeyedArchiver:

It has methods like encodeInt32:forKey: but no unsigned variants <rdar://6083905>.   (Good thing I filed the bug, I'm sure Apple will get right on it, eh Gwynne? :)  Sorry, couldn't resist.)

You have to watch out for sign extension.  This may surprise some people:

	uint32_t input = 0xFFFFFFFF; // 4294967295
	NSMutableData* data = [NSMutableData data];
	NSKeyedArchiver* archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
	[archiver encodeInt32:(int32_t)input forKey:@"test"];
	[archiver finishEncoding];

	NSKeyedUnarchiver* unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
	int64_t output = [unarchiver decodeInt64ForKey:@"test"];
	[unarchiver finishDecoding];

The value of output is _not_ 4294967295, it is -1.  This behaves correctly, but I bet lots of code out there casts uint32 to int32 like above.  If you want to encode a uint32 you need to use encodeInt64: I guess, which is not obvious.  The lack of encodeUInt64 is worst of all.

Cheers,

--
____________________________________________________________
Sean McBride, B. Eng                 email@hidden
Rogue Research                        www.rogue-research.com
Mac Software Developer              Montréal, Québec, Canada



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References: 
 >archiving report (From: "Gerriet M. Denkmann" <email@hidden>)

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