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My NSSwappedDouble decoding crashes on iPhone 4
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My NSSwappedDouble decoding crashes on iPhone 4


  • Subject: My NSSwappedDouble decoding crashes on iPhone 4
  • From: Markus Spoettl <email@hidden>
  • Date: Wed, 29 Sep 2010 02:41:33 -0400

Hello,

  I have a need to manually encode and decode double values archived using a NSKeyedArchiver. I can't use encodeDouble/decodeDouble in this case because of truly terrible performance in some previous releases of Mac OS (not sure if that's still the case in 10.6).

This worked well so far on all kinds of platforms including the iPhone 3G and 3GS. Values sent back and forth on the same and different platforms were correctly encoded/decoded every time. On the iPhone 4 the decoding crashes at the indicated location (according to the crash logs I have) and I have no idea why.

The the Mac code is 32bit and runs on Leopard and Snow Leopard.

- (void)encodeDouble:(double)value forKey:(NSString *)key withCoder:(NSCoder *)encoder
{
    NSSwappedDouble sd = NSSwapHostDoubleToLittle(value);
    [encoder encodeBytes:(const uint8_t *)&sd length:sizeof(NSSwappedDouble) forKey:key];
}

- (double)decodeDoubleForKey:(NSString *)key withCoder:(NSCoder *)decoder
{
    double result = 0.0;
    NSUInteger retsize;
    NSSwappedDouble *sd = (NSSwappedDouble *)[decoder decodeBytesForKey:key returnedLength:&retsize];
    if (retsize == sizeof(NSSwappedDouble)) {  // <=== crash
        result = NSSwapLittleDoubleToHost(*sd);
    }
    return result;
}

I'm sure this will be a humiliating exercise for me but I don't have the faintest clue what the problem might be and I could use some help. Thanks a lot for any insight.

Regards
Markus
--
__________________________________________
Markus Spoettl

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