#ifndef cpu_h
#define cpu_h

#include <cstdint>

struct cpu
{
    enum {INIT = 0};

    std::uint64_t rip, rsp, rbp, rbx, r12, r13, r14, r15;

    cpu() = default;

    std::uint64_t __attribute__((naked,noinline,returns_twice)) get()
    {
        asm volatile("mov (%%rsp),%0  \n"
                     "lea 8(%%rsp),%1 \n"
                     "mov %%rbp,%2    \n"
                     "mov %%rbx,%3    \n"
                     "mov %%r12,%4    \n"
                     "mov %%r13,%5    \n"
                     "mov %%r14,%6    \n"
                     "mov %%r15,%7    \n"
                     :"=r"(rip), "=r"(rsp), "=m"(rbp), "=m"(rbx), 
                      "=m"(r12), "=m"(r13), "=m"(r14), "=m"(r15));
        asm volatile("ret"::"a"(INIT)); // optional: first call returns INIT = 0
    }

    void __attribute__((naked,noinline,noreturn)) set(std::uint64_t ret = INIT + 1) const
    {
        asm volatile("mov %1,%%rsp \n"
                     "push %0      \n"
                     "mov %2,%%rbp \n"
                     "mov %3,%%rbx \n"
                     "mov %4,%%r12 \n"
                     "mov %5,%%r13 \n"
                     "mov %6,%%r14 \n"
                     "mov %7,%%r15 \n"
                     "mov %%rsi,%%rax \n" // optional: return value on get after set
                     "ret           \n"
                     :
                     :"m"(rip), "m"(rsp), "m"(rbp), "m"(rbx), 
                      "m"(r12), "m"(r13), "m"(r14), "m"(r15)
                     :"memory");
    }
};

#endif // cpu_h