Now that we've seen the problems, let's take a look at some of the solutions you can use.
The following header files are shipped standard with QNX Neutrino:
<gulliver.h>
Isolates big-endian vs little-endian issues.
<hw/inout.h>
Provides input and output functions for I/O or memory address spaces.
Determining endianness
The file <gulliver.h> contains macros to help resolve endian issues.
Swapping data if required
Suppose you need to ensure that data obtained in the host order (i.e., whatever is “native” on this machine) is returned in a particular order, either big- or little-endian. Or vice versa: you want to convert data from host order to big- or little-endian.
Accessing unaligned data
To access data on nonaligned boundaries, you have to access the data one byte at a time (the correct endian order is preserved during byte access).
Examples
Here are some examples showing how to access different pieces of data using the macros introduced so far.
Accessing I/O ports
When you're porting code that accesses hardware, the x86 architecture has a set of instructions that manipulate a separate address space called the I/O address space. This address space is completely separate from the memory address space. On non-x86 platforms, such an address space doesn't exist—all devices are mapped into memory.