On 18 Apr 2011, at 03:54, Quincey Morris <quinceymor...@earthlink.net> wrote:
>
> On Apr 17, 2011, at 13:09, JAMES ROGERS wrote:
>
>> char sndBuffer[65];
>> int j;
>>
>> characterIndex++; // is always sitting at the last character sent so
>> advance to the next character in string.
>> for (j = 0; j < 65; j++) {
>> sndBuffer[j] = [string characterAtIndex:characterIndex];
>> characterIndex++;
>> }
>> sndBuffer[j] = 0x00;
>> substring = [NSString stringWithUTF8String:sndBuffer];
>>
>> It works flawlessly, but there oughta be a way without reverting to C?
>
> This code is just wrong, BTW.
>
> The return value from -[NSString characterAtIndex:] is 'unichar', which is a
> 16-bit quantity, so assigning it to a 'char' variable isn't a good idea.
>
> Also, the return value is *not* a character, in the sense of being a Unicode
> code point. It's an element of the UTF-16 representation of the string. That
> means you can't just stop extracting elements at an arbitrary position,
> without potentially breaking the current substring and/or the next substring.
>
> Either you're going to have to analyze the sequence of elements manually
> according to the UTF-16 definition to find a good break point, or use
> something like -[NSString rangeOfComposedCharacterSequence...] (which doesn't
> do the same thing, but does guarantees a usable UTF-16 break point).
>
> Also, re-creating the NSString (substring) using a UTF-16 string but
> pretending it's a UTF-8 string isn't going to work very well.
>
> Also, it matters what's going to happen to your substring next. The UTF-8,
> UTF-16 and Unicode code point byte-lengths of a string are all different, so
> your assumptions about what fits into a fixed-size buffer need to be
> carefully re-examined.
>
I would suggest to convert the string into raw bytes, using NSString
dataUsingEncoding: NSUTF8StringEncoding , then NSData -bytes, then transmit the
bytes in appropriate chunks.
On the receiving end:
get some bytes, use NSMutableData appendBytes:length:
and finally, when all data have arrived, use NSString initWithData:encoding:
NSUTF8StringEncoding.
Gerriet.
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