Byte encoder for some basic types

encoder.cxx

#include <cstdint>
#include <type_traits>

/*
 * Encodes the value as bytes and inserts into the iterator.
 *
 * Example:
 *   std::vector<uint8_t> buf;
 *   int some_val = 0x12345678;
 *   encode(some_val, back_inserter(buf));
 *
 * © 2014 Matthew Brush
 */
template< typename ValueType,
          typename ByteIterator,
          typename SizeType = size_t,
          typename std::enable_if<
            std::is_integral<ValueType>::value
          >::type* = nullptr >
void encode(ValueType value, ByteIterator iter) {

  const SizeType bits_size(sizeof(ValueType) * 8);
  unsigned long long as_int = static_cast<unsigned long long>(value);
  for (SizeType shift=(bits_size - 8); shift != 0; shift-=8) {
    *iter = static_cast<uint8_t>((as_int >> shift) & 0xFF);
    ++iter;
  }
  *iter = static_cast<uint8_t>(as_int & 0xFF);
}

template< typename ByteIterator,
          typename SizeType = size_t >
void encode(float value, ByteIterator iter) {

  union { float as_dbl; uint32_t as_int; } u = { value };
  encode<uint32_t, ByteIterator, SizeType>(u.as_int, iter);
}

template< typename ByteIterator,
          typename SizeType = size_t >
void encode(double value, ByteIterator iter) {

  union { double as_dbl; uint64_t as_int; } u = { value };
  encode<uint64_t, ByteIterator, SizeType>(u.as_int, iter);
}

#ifdef __GNUC__
template< typename ByteIterator,
          typename SizeType = size_t >
void encode(long double value, ByteIterator iter) {

  const SizeType bits_size(sizeof(long double) * 8);
  union { long double as_dbl; unsigned __int128 as_int; } u = { value };
  for (SizeType shift=(bits_size - 8); shift != 0; shift-=8) {
    *iter = static_cast<uint8_t>((u.as_int >> shift) & 0xFF);
    ++iter;
  }
  *iter = static_cast<uint8_t>(u.as_int & 0xFF);
}
#endif

template< typename ByteIterator,
          typename CharType = char,
          typename SizeType = size_t >
void encode(const std::basic_string<CharType>& value, ByteIterator iter) {

  encode<uint32_t, ByteIterator, SizeType>(value.size(), iter);
  for (CharType ch : value)
    encode<CharType, ByteIterator, SizeType>(ch, iter);
}