NSData bytes method - (const void *)bytes returned pointer empty

Question

const unsigned char *rawImgNSDataBuffer=(unsigned char *)[self.RNGbyImage.rawImgNSData bytes];

I am attempting to read my NSData by calling the method - (const void *)bytes. What I did is assign the returned bytes to my own unsigned char pointer, so as to read bytes inside rawImgNSData from this pointer rawImgNSDataBuffer. However, the returned pointer rawImgNSDataBuffer has always 0 contents. It is not nil, but it never contains char values I expect. I would guarantee that my NSData is not nil and NSData has length > 0. I was trying hard to read it but not worked. Any help would be much appreciated.

Did you read the info in the description of NSData bytes? "A read-only pointer to the receiver’s contents.", meaning that if the NSData object goes away so does the char data. — Hot Licks

JJC JJC · Accepted Answer · 2014-03-12T01:00:14

If your rawImgNSDataBuffer is not nil, then things should be working fine. What do you mean that it has 0 contents? Are you viewing it in the debug area?

If you're printing out the contents and it displays nothing, it may just mean that the first bytes are '00' which in terms of char type, just means end of a string. However, it doesn't mean that there is no data there.

I suggest placing a breakpoint after your bytes call, then right-clicking on the rawImgNSDataBuffer variable in the debug area and selecting "View Memory of "rawImgNSDataBuffer"". You'll get a better picture of what the data actually looks like there.

NSData bytes method - (const void *)bytes returned pointer empty

1 Answers