/*
00000001 10000000 | 00000001 10000001
 0000001  0000000 |  0000001  0000001
  0000001 0000000 |    00000010000001
              128 |               129
*/

#include <cstdint>
#include <cstring>

int main() {
  constexpr int size = 2;

  char input[size] = {0b00000001, 0b10000000};

  int64_t res = 0;

  for (int i = 0; i < size; ++i) {
    int64_t byte = 0;

    std::memcpy(&byte, &input[i], sizeof(char));

    const bool eof = byte & (1 << 7);

    byte = byte & ~(1 << 7);
    res <<= i * 7;
    res |= byte;

    if (eof)
      break;
  }
}