CODEWITHSUNDEEP
c++vectorstl
Francisco Gomes
Francisco Gomes

Reputation: 55

C++11/14 convert std::uint32 to std::vector<std::uint8>

I would like to convert std::uint32 to std::vector<std::uint8> in a better way than this:

std::uint32_t base_rva = 0xccddee00;
std::vector<std::uint8_t> vraw_data;

//copying base_rva to raw_data
vraw_data.resize(sizeof(base_rva));
std::memcpy(vraw_data.data(), &base_rva, sizeof(base_rva));

I was looking for something like:

std::vector<std::uint8_t> vraw_data((std::uint8_t*)&base_rva, sizeof(base_rva));

Any suggestions?

Upvotes: 2

Views: 7064

Answers (2)

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

I was looking for something like:

std::vector<std::uint8_t> raw_data((std::uint8_t*)&base_rva, sizeof(base_rva));

There's no such constructor available for std::vector, but supposed you want to store the copy of a std::uint32_t internal representation in a std::vector<std::uint8_t> you can simply do

 std::uint32_t data = 42;
 std::vector<std::uint8_t> raw_data( (std::uint8_t*)&data
                                   , (std::uint8_t*)&(data) + sizeof(std::uint32_t));

according (4) from std::vector constructors.

Upvotes: 5

evan
evan

Reputation: 1673

If you don't like casting, you could do it like...

union to_byte_vector
{
  uint32_t val;
  uint8_t bytes[1];

  to_byte_vector() = default;
  to_byte_vector(uint32_t v) : val(v) {}
  to_byte_vector(const to_byte_vector& o) : val(o.val) {}
  to_byte_vector& operator=(const to_byte_vector& o) { val = o.val; return *this; }
  operator uint32_t() const { return val; }
  std::vector<uint8_t> get_vector() const { return std::vector<uint8_t>(begin(), end()); }

private:
  const uint8_t* begin() const { return bytes; }
  const uint8_t* end() const { return bytes + sizeof(uint32_t); }
};

And use it like...

auto vec = to_byte_vector(42).get_vector();

But really, this is just letting the union do the casting work for you.

Upvotes: 0

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