Improve this answer. Ray 1 1 silver badge 11 11 bronze badges. Cody Gray Cody Gray 3, 14 14 silver badges 27 27 bronze badges. Use stdint. The only way of 'protection' is converting the macro into an inline function, as Cody Gray describes in this answer.
Should code pass a int, unsigned short, char etc. Cody Gray 3, 14 14 silver badges 27 27 bronze badges.
If the data was misaligned on the recipient architecture, the moment you tried to read from it, you'd take an exception or pay a very steep speed penalty. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses.
Featured on Meta. So here in this example, if we get a value 1 after dereferencing the typecasted variable i we can be sure that the machine is a little endian machine or otherwise. Your email address will not be published. This C program shows a very simple program to detect the endianness of the system. Leave a Reply Cancel reply 0 Your email address will not be published. Save my name and email in this browser for the next time I comment.
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Cool, that's good info for anyone developing a closed source product which doesn't need to be portable or standards compliant. Alok, OP did not mention the compiler OS. A person is allowed to give answers according to his experience with a particular set of tools.
Show 7 more comments. What joke? Nodejs uses this technique! Paul Paul 31 1 1 bronze badge. I think you mean char , not byte. Using this strategy, the solution with most votes compared to yours is equivalent and the most efficient and portable. However the solution I propose second most votes needs less operations and should be more efficient. This code snippet can convert 32bit little Endian number to Big Endian number.
Kaushal Billore Kaushal Billore 31 6 6 bronze badges. Thanks YuHao I am new here, don't know how to format the Text. Most compilers would do this, though, but some simple compilers are not able to optimize it for you.
Code relies on a very reasonable assumption: source is aligned as needed - yet if that assumption does not hold, the code is UB. Ok, I added the missing includes. Note that LL not needed in the constant. You're right chux. As for the LL, it's more an annotation than anything else. It's also a habit I catched from a long time ago with buggy compilers pre standard which would not do the right thing.
John Knoeller John Knoeller The Overflow Blog. Stack Gives Back Safety in numbers: crowdsourcing data on nefarious IP addresses. Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Reverse the Endianness of a C structure Ask Question.
Asked 8 years, 3 months ago. Active 8 years, 3 months ago. Viewed 11k times. Improve this question. James James 3, 3 3 gold badges 33 33 silver badges 70 70 bronze badges.
Add a comment. Active Oldest Votes. I think there may be two issues here depending on how you're sending this data over TCP. Issue 1: Endianness As, you've said endianness is an issue. To use these functions you will need to do something like the following Sender: t.
Issue 2: Data alignment The article "Data alignment: Straighten up and fly right" is a great read for this one Improve this answer. Jimbo Jimbo 4, 3 3 gold badges 21 21 silver badges 44 44 bronze badges.
To deal with the alignment issue, most compilers also have some mechanism for specifying alignment, and in particular for specifying packed alignment ie, no padding. Note that this can introduce portability issues however Thank you for a very detailed and clear answer. I was unclear as to whether the actual order of the bits in the byte had to be swapped, or just the bytes, thanks for clearing that up.
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