Obj-C Read Little Endian From Binary File? (xcode)

Question

I'm looking for a way to get an int value from a binary file. So lets say i have this file "myfile.dat" where from my PC i stored a lot of stuff... Now i need to read that file from my IPhone and show the data...

on the "myfile.dat" i have this (binary and all ints are little endian): 0-12: A signature string 13-16: An int number (note that length = 4)

So using NSData i know i can read from pos 13 to pos 16 and get those bytes... i can get the first 0-12 string correctly, but i cannot read pos 13-16 and convert it to an int value in Obj-C.... ;(

I have something like:

unsigned char bytes[length];
[_data getBytes:bytes range:NSMakeRange(offset, length)];
int32_t elem = OSReadLittleInt32(bytes, 0);

Now, im a newbie when it comes to Obj-C and C/C++... all my life i have been working with C# (sad)...

Can anyone help? THANKS IN ADVANCE!

Jef · Accepted Answer · 2011-11-09 16:43:05Z

4

Give this a try:

unsigned long bytes;
[_data getBytes: &bytes length: sizeof(unsigned long)];

NSLog(@"%i", NSSwapLittleLongToHost(bytes));

answered Nov 9, 2011 at 16:43

Jef

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3 Comments

rzumbado Over a year ago

I still get some wrong number: 544106784. Which is wrong.. the right number i'm looking for is 333.

Jef Over a year ago

Can you add the output of NSLog(@"data: %@", [_data description])?

rzumbado Over a year ago

Oh boy, you are going to hate me... i was storing the values in the wrong order (on the file)... So this method of yours works just fine. So thank you very much :) you rock!

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