Re: MD5

[David Ayers]

Richard Frith-Macdonald wrote:

> I already added a simple category of NSData to the Additions library, 
> consisting only of an -MD5Digest method returning an NSData object. 

Cool, I'll try to get a gsweb patch in soon...

> I'm not sure what the other methods are supposed to do exactly ... the 
> string encoding makes sense where the string is the input to the 
> digest ... but what to do when producing string output?  I don't think 
> there is any standard format for representing a digest as a string, 
> unless it's to encode the bytes as pairs of hex digits.
> certainly, you can't just use [NSString-initWithData:encoding:] to 
> produce a string as you have no guarantee that the bytes of the digest 
> are valid characters in the encoding you specify. 

Actually yes, I did fall into that trap here :-).  What I actually meant 
would probably be something like

@implementation NSData (MD5)
...
- (NSString *)md5String
{
return [[self md5Digest] hexadecimalStringRepresentation]
}
@end
and at that point the encoding wouldn't hav to be dealt with.

and maybe:
@implementation NSString (MD5)
- (NSString *)md5StringUsingEncoding: (NSStringEncoding) enc
{
 return [[self dataUsingEncoding: enc] md5String];
}
- (NSString *)md5String
{
 return [[self dataUsingEncoding: [isa defaultCStringEncoding] md5String];
}