Re: Arbitrary length ints from NSData

[Quincey Morris]

On Aug 13, 2009, at 11:25, Chase Meadors wrote:

I'm afraid you'll have to explain the multiply-by-256-and-add  
technique.

I mean something like this (untested):

        unsigned char *bytes = [self bytes];
        int byteIndex = [self length];
        int result = 0;
        BOOL firstByte = YES;

        while (byteIndex--) {
                if (firstByte) {
			result = (signed char *) bytes [byteIndex]; // signed the first  
time
                        firstByte = NO;
                }
                else
			result = result * 0x100 + bytes [byteIndex]; // unsigned the rest  
of the times
        }
        
        return [NSNumber numberWithInt: result];

BTW, I didn't notice that you'd originally declared 'result' as  
unsigned int, so my first suggestion wouldn't have have worked unless  
you also changed 'result' to a signed int.

P.S. I see Alastair gave you a mostly better answer already. However,  
I'll point out that if you have any *3-byte* numbers (I see "arbitrary  
length ints" in the subject line) you're not going to find an  
OSReadLittleInt24 to help you.


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