varnum.hpp

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#ifndef NDNPH_TLV_VARNUM_HPP
#define NDNPH_TLV_VARNUM_HPP
 
#include "../core/common.hpp"
 
namespace ndnph {
namespace tlv {
 
constexpr size_t
sizeofVarNum(uint32_t n) {
  return n < 0xFD ? 1 : n <= 0xFFFF ? 3 : 5;
}
 
inline void
writeVarNum(uint8_t* room, uint32_t n) {
  if (n < 0xFD) {
    room[0] = n;
  } else if (n <= 0xFFFF) {
    room[0] = 0xFD;
    room[1] = n >> 8;
    room[2] = n;
  } else {
    room[0] = 0xFE;
    room[1] = n >> 24;
    room[2] = n >> 16;
    room[3] = n >> 8;
    room[4] = n;
  }
}
 
inline int
readVarNum(const uint8_t* input, size_t size, uint32_t& n) {
  if (size >= 1 && input[0] < 0xFD) {
    n = input[0];
    return 1;
  }
  if (size >= 3 && input[0] == 0xFD) {
    n = (static_cast<uint32_t>(input[1]) << 8) | static_cast<uint32_t>(input[2]);
    return 3;
  }
  if (size >= 5 && input[0] == 0xFE) {
    n = (static_cast<uint32_t>(input[1]) << 24) | (static_cast<uint32_t>(input[2]) << 16) |
        (static_cast<uint32_t>(input[3]) << 8) | static_cast<uint32_t>(input[4]);
    return 5;
  }
  return 0;
}
 
} // namespace tlv
} // namespace ndnph
 
#endif // NDNPH_TLV_VARNUM_HPP