C++ 32-bit word byte swapping [duplicate]

Question

Possible Duplicate:
How do I convert between big-endian and little-endian values in C++?

I was wondering how you would byte swap a 32-bit word

I have a huge buffer of these words and each of them need to be byte swapping due to endianness.

Thomas Russell · Accepted Answer · 2012-07-09 14:49:10Z

Either use the functions provided by your OS (cf. Martin Beckett's answer), or alternatively, if you are looking for a way to do this out of interest you may be interested in the following code snippet:

x = (x & 0x0000FFFF) << 16 | (x & 0xFFFF0000) >> 16; x = (x & 0x00FF00FF) << 8 | (x & 0xFF00FF00) >> 8;

Yeah, to complete the byte swapping a second line is needed: x = (x & 0x00FF00FF) << 8 | (x & 0xFF00FF00) >> 8;

Martin Beckett · Accepted Answer · 2012-07-09 14:34:30Z

0

Use htonl / ntohl provided by your OS

answered Jul 9, 2012 at 14:34

Martin Beckett

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3 Comments

Mike Seymour Over a year ago

That will only swap bytes if the native format is the reverse of network format.

Martin Beckett Over a year ago

@MikeSeymour true, but it's most likely that this is what the user needs. Anyone writing some low level non-network order driver is likely to know how to do it anyway. This seemed a good 99% answer

user1496413 Over a year ago

Well actually I am writing a low level non-network order driver... For an internship though so its above my head. I understand the concept but I am used to high level languages.

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