iOS issues having large uint8_t[ ] array - iphone

Question

Actually I m receiving huge byte array as long as 35 mb in size. This byte array is bytes of a pdf document. I m receiving this from tcp socket input stream.
The code I m using is
+ (NSString *) recvToFile:(NSString *)_fileName: (long)_sz {
#try {
uint8_t t[_sz];
NSMutableData *data = nil;
NSMutableData *fileData = [[NSMutableData alloc] init];
long _pos = 0;
NSString *_fullPath = [Misc createTempFile:_fileName];
while (_sz > _pos) {
long _c = [m_sin read:t maxLength:_sz];
_pos += _c;
data = [NSData dataWithBytes:t length:_c];
if([Misc checkTempFileExists:_fileName]==nil)
[[NSFileManager defaultManager] createFileAtPath:_fullPath contents:nil attributes:nil];
[fileData appendData:data];
}
[fileData writeToFile:_fullPath atomically:YES];
NSDictionary *attr = [[NSFileManager defaultManager] attributesOfItemAtPath:_fullPath error:nil];
NSLog(#"ATTR - %#",attr);
long long length = [[attr valueForKey:#"NSFileSize"] intValue];
if (length >= _sz)
return (_fullPath);
}
#catch (NSException * e) {
}
return (nil);
}
The problem is that the app crashes giving "EXC_BAD_ACCESS(code=2 address=0x2461ae4)" error at first line that is
+(NSString *) recvToFile:(NSString *)_fileName: (long)_sz
When i explicitly declare the size of uint8_t array to 800000 as uint8_t[800000];
then it works in my iOS simulator but not on my iPad
Please help. Thanks

Answer 1

You are most likely running out of stack space. Even if you allocated the memory on the heap, 35MB is quite a lot for iOS devices. You should write the data out to a file rather than an in-memory buffer.
UPDATE:
So it looks like this code can already chunk the data and write it to the file in small pieces. All you have to do is change from this:
uint8_t t[_sz];
To something like this:
uint8_t t[CHUNK_SIZE];
where CHUNK_SIZE can be something reasonable like a few KB.

Answer 2

This line looks wrong to me:
(NSString *) recvToFile:(NSString *)_fileName: (long)_sz {
You should have something like:
+ (ReturnType *) methodname:(Type) _var1 secondArg:(type) _var2
So maybe you want:
+ (NSString *) recvToFile:(NSString *)_fileName size:(long)_sz
I think the reason you're getting a crash is that you're trying to read a variable called _sz. By changing this to a fixed value you're not reading it here, and by some miracle the rest of your code is running.
Looking at your code I think you might need a refresher on some of basics of objective C syntax. Maybe you're more familiar with another language? I'm told by my iOS colleagues that try and catch are used rarely in objective C, and the way you've used them could create various problems.