How to convert NSData to byte array in iPhone?

Question

I want to convert `NSData` to a byte array, so I write the following code: ``` NSData *data = [NSData dataWithContentsOfFile:filePath]; int len = [data length]; Byte byteData[len]; byteData = [data bytes]; ``` But the last line of code pops up an error saying "incompatible types in assignment". What is the correct way to convert the data to byte array then?

Accepted Answer

You can't declare an array using a variable so `Byte byteData[len];` won't work. If you want to copy the data from a pointer, you also need to memcpy (which will go through the data pointed to by the pointer and copy each byte up to a specified length).

Try:

```
NSData *data = [NSData dataWithContentsOfFile:filePath];
NSUInteger len = [data length];
Byte *byteData = (Byte*)malloc(len);
memcpy(byteData, [data bytes], len);
```

This code will dynamically allocate the array to the correct size (you must `free(byteData)` when you're done) and copy the bytes into it.

You could also use `getBytes:length:` as indicated by others if you want to use a fixed length array. This avoids malloc/free but is less extensible and more prone to buffer overflow issues so I rarely ever use it.

How to convert NSData to byte array in iPhone?

Solution

Problem