Re: Need localization-proof method of transporting dates.
Re: Need localization-proof method of transporting dates.
- Subject: Re: Need localization-proof method of transporting dates.
- From: Greg Guerin <email@hidden>
- Date: Sun, 5 Apr 2009 18:18:51 -0700
Michael Ash wrote:
@implementation NSDictionary (SHA1Hashing)
- (NSData *)gc_sha1hash {
NSMutableData *subhashes = [NSMutableData data];
for(id key in [[self allKeys]
sortedArrayUsingSelector:@selector(compare:)]) {
[subhashes appendData:[key gc_sha1hash]];
[subhashes appendData:[[self objectForKey:key] gc_sha1hash]];
}
return [subhashes gc_sha1hash];
}
@end
Then define -gc_sha1hash for all the other classes you expect to
encounter as well. (The prefix is just to ensure that you don't
overwrite a hypothetical Apple implementation of a -sha1hash method.)
As a design, it might be more flexible to define a -gc_canonicalData
method that returns an NSData containing unhashed canonical bytes,
rather than -gc_sha1hash that returns a hash. This would make it
easier to use different secure-hash algorithms, should that be
desired. SHA1 isn't exactly state-of-the-art.
I'd also make the code that calculates the hash from a given
NSDictionary or NSArray return an error (or throw an exception) if
anything in the collection doesn't respond to -gc_canonicalData. Or
it could silently skip those (not hash them), depending on the context.
-- GG
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