Convert a double to bytes and back in C

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HoboBen	Created : 06 December 2010 System : Server Based Language : Monkey Convert a double to bytes and back in C
By using a C union data structure, it's simple to convert a double to its raw bytes and back. Note that the actual order of bytes varies depending on machine endianness. #include <stdlib.h> #include <stdio.h> union { double d; unsigned char byte[sizeof(double)]; } doubleConverter; int main(void) { int i; doubleConverter.d = (22.0 / 7.0); printf("Double: %f\n", doubleConverter.d); printf("Bytes: "); for (i = 0; i < sizeof(double); i++) { printf("%d ", doubleConverter.byte[i]); } printf("\n"); /* Mess it up... */ doubleConverter.byte[0] = 119; doubleConverter.byte[1] = 190; doubleConverter.byte[2] = 159; doubleConverter.byte[3] = 26; doubleConverter.byte[4] = 47; doubleConverter.byte[5] = 221; doubleConverter.byte[6] = 94; doubleConverter.byte[7] = 64; printf("Edited Double: %f\n", doubleConverter.d); } --v

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Tuesday, 07 December 2010, 17:38
Evil Roy Ferguso	C++ lets you apply this pattern to a slightly more ridiculous extreme. #include <iostream> #include <algorithm> #include <functional> #include <random> template <typename T> struct evil_converter { union { T value; unsigned char bytes[sizeof(T)]; }; }; template <typename T> std::ostream& operator<<(std::ostream& out, evil_converter<T> const& bah) { out << bah.value << std::endl; std::for_each(bah.bytes, bah.bytes + sizeof(T), [&out](unsigned char b){ out << (int)b << " "; }); return out; } int main() { typedef double the_type; evil_converter<the_type> bah; bah.value = 37; std::cout << bah << std::endl; std::cout << "Muck it up" << std::endl; std::uniform_int_distribution<unsigned char> distribution(0, 255); std::generate_n(bah.bytes, sizeof(the_type), std::bind(distribution, std::mt19937())); std::cout << bah << std::endl; } --v

Convert a double to bytes and back in C

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