Removing non-ascii characters from NSData?

Question

First off, I'm not exactly sure what is happening or if I fully understand it enough to describe the issue so I'll try my best.

I'm encoding a NSData object that contains json and one of the objects contains a degree symbol. We believe this what is causing the issue and would like to remove it before encoding since the problem occurs during encoding.

I have plenty of options out there for removing certain characters from strings but none from doing it from the NSData object itself. Wondering if this is even possible or if its an issue with how I'm already encoding it.

This is how the NSData object is being encoded and turned back into a NSData object to serialize it to json. Right now I'm not trying to remove the degree symbol, using Latin 1 because another character I want to use but do not need it, this probably isn't the best way to do but it works for majority of other data objects that pass through it just not this one so this needs to change.

NSString* stringISOLatin1 = [NSString stringWithCString:data.bytes encoding:NSISOLatin1StringEncoding];
NSData* dataUTF8 = [stringISOLatin1 dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];

The results are a little weird, most of the time it works fine, even including the degree symbol in the text when displayed on screen. Other times after encoding the string comes back messed up at the end which makes it unable to be serialized.

Any help would be appreciated even if it just leads to a better explanation of what is happen. Thanks

Answer 1

The problem is likely that you are using NSString:stringWithCString:encoding: to convert your data object. This function requires the data to be null terminated. NSData objects do not have to be NULL terminated because they have an explicit length. If the NULL character is missing it will continue to read whatever there happens to be after the string, giving you either garbage at the end or possibly crash because of memory violation.

Instead try using this:

NSString *stringISOLatin1 = [[NSString alloc] initWithData:data encoding:NSISOLatin1StringEncoding];