How to properly split up NSData? - ios

Question

I'm trying to split up NSData into smaller <100 length chunks so I can send them over CoreBluetooth but for some reason, it decides to mess up occasionally, proven by the fact that trying to combine the data and decoding the object from within the same method fails. Because of this, I'm assuming I'm splitting up the NSData wrong?
Here is the code I'm using to split it up (Taken from some kind stranger on stackoverflow!)
// Split up the data and put into Array
NSUInteger length = [data length];
NSUInteger chunkSize = 100;
NSUInteger offset = 0;
do {
NSUInteger thisChunkSize = length - offset > chunkSize ? chunkSize : length - offset;
NSData* chunk = [NSData dataWithBytesNoCopy:(char *)[data bytes] + offset
length:thisChunkSize freeWhenDone:NO];
offset += thisChunkSize;
[orderQueue addObject:chunk];
} while (offset < length);
The data is then recombined and the object unarchived as so:
NSMutableData *finishedData = [[NSMutableData alloc] init];
for (NSData *dataChunk in orderQueue) {
[finishedData appendData:dataChunk];
}
Order *order = [NSKeyedUnarchiver unarchiveObjectWithData:finishedData]; // ERRORS OUT ON THIS LINE
finishedData = [[NSMutableData alloc] init];
dataChunks = [[NSMutableArray alloc] init];
On paper, I honestly think I'm doing it right but it still bugs out occasionally. Any ideas why this might be? :< I get the following error:
* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[NSKeyedUnarchiver initForReadingWithData:]: incomprehensible archive (0x62, 0x70, 0x6c, 0x69, 0x73, 0x74, 0x30, 0x30)'

Answer 1

I just ran this code to check your logic and it's correct.
NSMutableArray *orderQueue = [[NSMutableArray alloc] init];
NSString *originalString = #"Here are some strings for you.";
for (NSInteger i = 0; i < 1000; ++i)
{
#autoreleasepool {
originalString = [originalString stringByAppendingString:#"\nHere are some strings for you."];
}
}
NSData *data = [originalString dataUsingEncoding:NSUTF8StringEncoding];
// Split up the data and put into Array
NSUInteger length = [data length];
NSUInteger chunkSize = 100;
NSUInteger offset = 0;
do {
NSUInteger thisChunkSize = length - offset > chunkSize ? chunkSize : length - offset;
NSData* chunk = [NSData dataWithBytesNoCopy:(char *)[data bytes] + offset
length:thisChunkSize freeWhenDone:NO];
offset += thisChunkSize;
[orderQueue addObject:chunk];
} while (offset < length);
NSMutableData *finishedData = [[NSMutableData alloc] init];
for (NSData *dataChunk in orderQueue) {
[finishedData appendData:dataChunk];
}
NSString *recreatedString = [[NSString alloc] initWithData:finishedData encoding:NSUTF8StringEncoding];
NSLog(#"%#", recreatedString);
NSLog(#"%#", [originalString isEqualToString:recreatedString] ? #"Equal" : #"Error");
Your error must be somewhere else, potentially in the way you're responding to the <NSCoding> protocol in the Order class.