Le 26/01/2017 à 01:05, Vicente J. Botet Escriba a écrit :

Le 26/01/2017 à 00:04, Vicente J. Botet Escriba a écrit :

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Hi,

I wanted to put an Int wrapper inside a endian_buffer and I have some compiler errors depending on whether it is aligned ort not.

http://melpon.org/wandbox/permlink/k52wH2A7yagL2vMP

I was expecting that the endian_buffer would make abstraction of the wrapped type and consider it just as a sequence of bytes, but it seems that it instead works only for some builtin integral.

Am I missing something? Was this restriction intended? Could this restriction be removed and if yes, how?

I have reached to fix the aligned case adding the customization

Int endian_reverse(Int x) { using boost::endian::endian_reverse; return Int {endian_reverse(x.value)}; }

However for the unaligned case there is yet the shift error

prog.cc:30:28: required from here /usr/local/boost-1.61.0/include/boost/endian/buffers.hpp:231:26: error: invalid static_cast from type 'Int' to type 'char' *(bytes - 1) = static_cast<char>(value); ^~~~~~~~~~~~~~~~~~~~~~~~ /usr/local/boost-1.61.0/include/boost/endian/buffers.hpp:232:59: error: no match for 'operator>>' (operand types are 'Int' and 'int') next::store_big(bytes - 1, static_cast<T>(value >> 8)); ~~~~~~^~~~ /usr/local/boost-1.61.0/include/boost/endian/buffers.hpp:202:5: note: candidate: template std::basic_istream& boost::endian::operator>>(std::basic_istream&, boost::endian::endian_buffer&) operator>>(std::basic_istream& is, ^~~~~~~~

http://melpon.org/wandbox/permlink/iPwgdVBV91wsRxeC

I have added whatever was missing struct Int { int value; // Needed by unaligned Int() = default; Int(int i) : value (i) {} explicit operator char() { return value; } int operator >>(int n) { return value >> n; } int operator <<(int n) { return value << n; } friend Int endian_reverse(Int x) { using boost::endian::endian_reverse; return Int {endian_reverse(x.value)}; } }; http://melpon.org/wandbox/permlink/erLEWpc1oaR64iMW While Int() = default; explicit Int(int i) : value (i) {} are natural on a wrapped opaque int, the implicit conversion is less desirable as well as the conversions to char and the shift operations. Int(int i) : value (i) {} explicit operator char() { return value; } int operator >>(int n) { return value >> n; } int operator <<(int n) { return value << n; } I believe that the conversion could be explicit and that the implementation could use reinterpret_cast instead of static_cast, as we are reinterpreting the bits. IMHO, the shift shouldn't be required. It should be an implementation detail. BTW, is there any reason endian_buffer doesn't define equality operators? Vicente