I need someone to check if my program works on big-endian (Mac)
Author
Hey all, I've been working on a hiscore system. It saves the hiscores to a binary file using a format and process I made myself. It tries to take into account both big and little endian systems. It works fine on my PC, which is little endian. I was hoping to get someone with a big-endian system (like a Mac) to test it out and make sure it works. If possible, please download it and test it out. You should just be able to put all the files together in a project using your favorite IDE or into a makefile for make, and compile them. They don't have any windows-only code.
Thanks a lot, I appreciate it!
I have a windows machine, but I still have a couple suggestions. I don't think that code would work quite the way you think it would.
Here's some changes I think would help you, this still isn't the optimal solution, but its the first thing that popped into my head
[EDIT]
Odd, well if it works it works I guess.. =) I could have sworn you should have been going out of bounds in a couple of spots there...
[/EDIT]
[Edited by - moeron on June 10, 2005 10:13:26 AM]
// always specify the sign of a char in these cases...some systems have // different defaultschar * ReverseByteOrder( const char * bytes ){ // whats this for? char swap; // what if bytes isn't null terminated? Or what if its terminated too early? unsigned int length = std::strlen(bytes); // this points at one byte? char * ret = new char[1]; // going out of bounds here std::strcpy(ret, bytes); for ( unsigned int i = 0, j = length-1; i < length; ++i, --j ) { ret = bytes[j]; } return ret;}Here's some changes I think would help you, this still isn't the optimal solution, but its the first thing that popped into my head
#include <iostream>#include <bitset>#include <exception>#include <climits>using std::bitset;using std::cout;using std::endl;using std::cerr;void * ReverseByteOrder(const void *pValue, const std::size_t numBytes){ if( 0 == pValue ) throw(std::exception(__FUNCTION__)); std::size_t i, j = numBytes-1; const unsigned char *pData = reinterpret_cast<const unsigned char*>(pValue); unsigned char *pRetVal = new unsigned char[numBytes]; for(i=0; i < numBytes; ++i, --j ) pRetVal = pData[j]; return(pRetVal);}int main(){ unsigned int before = 1, *pAfter = NULL; std::bitset<sizeof(int) * CHAR_BIT> b; try{ b = before; cout << "Before swap\t" << b << endl; pAfter = (unsigned int*)ReverseByteOrder( &before, sizeof(before)); b = *pAfter; cout << "After swap\t" << b << endl; } catch(std::exception &e) { cerr << e.what() << endl; } catch(...) { cerr << "An unknown exception has occurred" << endl; } delete [] pAfter; return(0);}[EDIT]
Odd, well if it works it works I guess.. =) I could have sworn you should have been going out of bounds in a couple of spots there...
[/EDIT]
[Edited by - moeron on June 10, 2005 10:13:26 AM]
Hello,
I didn't look at your code, sorry. Here is the output on a 32-bit big endian machine (G4 PPC):
Mary has 1904 points.
Ben has 18 points.
John has 18 points.
Bip has 9 points.
Jeremy has 8 points.
Bob has 8 points.
Hope this helps.
I didn't look at your code, sorry. Here is the output on a 32-bit big endian machine (G4 PPC):
Mary has 1904 points.
Ben has 18 points.
John has 18 points.
Bip has 9 points.
Jeremy has 8 points.
Bob has 8 points.
Hope this helps.
Author
Sweet! Guess it works. Anyone else give it a try? I would have rated you up anonymous, but you are anonymous :) ++rate for moeron, though. I appreciate it.
I couldn't get hiscoresystem.cpp to compile, got the following warnings and errors from g++:
hiscoresystem.cpp: In member function `bool HiscoreSystem::Load()':
hiscoresystem.cpp:153: warning: comparison between signed and unsigned integer
expressions
hiscoresystem.cpp:173: error: type specifier omitted for parameter `score'
hiscoresystem.cpp:174: error: no matching function for call to `
std::vector<Hiscore, std::allocator<Hiscore> >::push_back(Hiscore
(&)(std::basic_string<char, std::char_traits<char>, std::allocator<char> >))
'
/usr/include/c++/3.3.2/bits/stl_vector.h:596: error: candidates are: void
std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = Hiscore, _Alloc
= std::allocator<Hiscore>]
Maybe i'm forgetting something, i'll come back and look at it when I get the chance.
hiscoresystem.cpp: In member function `bool HiscoreSystem::Load()':
hiscoresystem.cpp:153: warning: comparison between signed and unsigned integer
expressions
hiscoresystem.cpp:173: error: type specifier omitted for parameter `score'
hiscoresystem.cpp:174: error: no matching function for call to `
std::vector<Hiscore, std::allocator<Hiscore> >::push_back(Hiscore
(&)(std::basic_string<char, std::char_traits<char>, std::allocator<char> >))
'
/usr/include/c++/3.3.2/bits/stl_vector.h:596: error: candidates are: void
std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = Hiscore, _Alloc
= std::allocator<Hiscore>]
Maybe i'm forgetting something, i'll come back and look at it when I get the chance.
Author
I've made some code changes - found one of the errors you mentioned. If you could re-download it, that would be great, because the line numbers have changed :) The original link should work fin.
I really appreciate you taking the time to do this, though. Thanks again!
I really appreciate you taking the time to do this, though. Thanks again!
Your code relies on having a null terminated byte string (unsigned int length = std::strlen(bytes);)
Try this, it's more type safe than your solution - you should declare this in an anonymous namesapce and have wrappers for it only for types that it makes sense to endian-swap:
Try this, it's more type safe than your solution - you should declare this in an anonymous namesapce and have wrappers for it only for types that it makes sense to endian-swap:
template<class T>T& ReverseByteOrder(T& value){ unsigned char* ptr = reinterpret_cast<unsigned char*>(&value); size_t index = 0; for(;index<(sizeof(T)/2);++index) { std::swap(ptr[index],ptr[size - index -1]); } return value;}template<class T>T ReverseByteOrder_copy(const T& value){ T value_copy = value; ReverseByteOrder(value_copy); return value_copy;}I don't have access to the actual code I use right now, so I had to write this from memory, but hopefully you get the idea.
Author
Quote:Original post by Anonymous Poster
the endian won't and doesn't matter
Why not? I posted something on this a while ago and everyone told me it would. Anyways, I tried this:
entries_to_write = ReverseByteOrder_copy<int>(entries_to_write);
and similar on all the lines where I needed to reverse the byte order (changing <int> to <char*> when neccessary), but it gave me a bunch of linker errors, like this for example:
[Linker error] undefined reference to `int ReverseByteOrder<int>(int const&)'
I can't think of how I'm supposed to change the statement so it will work. Can you give me an example? Thanks.
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